All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Additional Problems
Consider 2 Al (s) + 6 HCl (ℓ) → 2 AlCl3 (s) + 3 H2 (g) the reaction of 4.5 mol Al with excess HCl to produce hydrogen gas. What is the pressure of H2(g) if the hydrogen gas collected occupies 14L at 300K? 1. 0.0763 atm 2. 0.233 atm 3. 5.28 atm 4. 7.9 atm 5. 11.9 atm 6. 1.07 atm
A 2.85-g sample of an unknown chlorofluorocarbon decomposes and produces 564mL of chlorine gas at a pressure of 752mmHg and a temperature of 298 K. What is the percent chlorine (by mass) in the unknown chlorofluorocarbon? 
Consider the reaction: 2 SO2(g) + O2(g) → 2 SO3(g) b. If 187.2 mL of SO3 is collected (measured at 315 K and 50.0 mmHg), what is the percent yield for the reaction? 
Ammonium nitrate decomposes explosively upon heating according to the balanced equation:  2 NH4NO3(s) → 2 N2(g) + O2(g) + 4 H2O(g) Calculate the total volume of gas (at 125 °C and 748 mmHg) produced by the complete decomposition of 1.55 kg of ammonium nitrate.   
For the reaction of Ca with excess HCI, determine the volume of H  2 gas that will be produced at 1.00  atm and 18°C when 12.2 g of Ca are reacted. Ca (s)  + HCI (l) →  CaCl2 (s)  + H2(g)
How many milliliters of ozone gas at 25.0°C and 1.00 atm pressure are needed to react with 45.00 mL of a 0.100 M aqueous solution of I- according to the chemical equation shown below? O3(g) + 2 I-(aq) + H2O(l) → O2(g) + I2(s) + 2 OH-(aq)
What volume of N2 measured at 735 mm Hg and 260°C, is produced when 70.0 g NaN3, is decomposed? 2NaN3(s) → 2Na(l) + 3 N2(g)   a) no given answer is close b) 0.0359 L c) 41.0 L d) 18.2 L e) 27.3 L
The following equation shows the combustion of methane. CH4 (g) + 2O2(g) → CO2(g) + 2H2O(g) If 6.0 g of CH4 reacts completely, what is the final pressure of the CO 2 produced and collected in a 1.4 L container at a temperature of 21°C?  
Assume this reaction is carried out in the apparatus diagram below. Nitric acid is produced commercially by the Ostwald process. In the first step, ammonium is oxidized to nitric oxide: 4 NH 3(g) + 5 O 2(g) → 4 NO(g) + 6 H 2O(g) The stopcock between the two reaction containers is opened, and the reaction proceeds using proper catalysts. Calculate the partial pressure of NO after the reaction is complete. Assume 100% yield for the reaction, assume the final container volume is 3.00 L, and assume the temperature is constant. 1. 0.333 atm 2. 0.500 atm 3. 0.250 atm 4. 0.400 atm 5. 1.50 atm
Sulfur dioxide reacts with oxygen gas to produce sulfur trioxide. What volume of oxygen gas will react with 15.0 L of sulfur dioxide if both gases are at 101.3 kPa and 125ºC? 1. 30.0 L 2. 7.50 L 3. 5.00 L 4. 15.0 L 5. 3.75 L
A 3.57 g sample of KCl-KClO3  mixture is decomposed by heating and produces 119 mL O2(g), measured at 22.4°C and 738 mm Hg. What is the mass percent of KClO 3 in the mixture assuming that all the KClO3 decomposes according to the following equation. KClO3(s) → KClO(s) + O2(s) a) no given answer is close b) 38.2% c) 16.4% d) 19.1 % e)  32.8%
For the decomposition of hydrogen peroxide reaction below, the reaction is slow unless a catalyst is present.  2H2O2(aq) →  2H 2O(l) + O 2(g) A.  If a catalyst is added to 154 mL of 0.882 M H 2O 2(aq), how many moles of O 2(g) are produced, assuming the reaction goes to completion?       B. The oxygen gas from the above procedure was collected and dried to remove water vapor. The volume of O2(g) was 726 mL at 23.9°C and 735 mmHg. Determine the amount (moles) of O  2 gas collected.       C. What was the percent yield for the reaction?         D. Why was it necessary to remove the water vapor?      
What volume of pure oxygen gas (O2) measured at 580 K and 1.00 atm is formed by complete dissociation of 4.0 mol of Ag2O? 2 Ag2O(s) → 4 Ag(s) + O2(g) 1. 381 L 2. 95.2 L  3. 190 L 4. 2 L 5. 128 L 6. 44.8 L
Oxygen gas reacts with powdered aluminum according to the reaction:  4 Al(s) + 3 O2(g) → 2 Al2O3(s) What volume of O2 gas (in L), measured at 782 mmHg and 25 °C, completely reacts with 53.2 g AI?
A 6.54 g sample of a mixture of magnesium carbonate and calcium carbonate is treated with excess hydrochloric acid. The resulting reaction produces 1.73 L of carbon dioxide gas at 28 oC and 744 torr pressure.Assuming that the reactions are complete, calculate the percentage by mass of magnesium carbonate in the mixture.
A 2.90 -g sample of an unknown chlorofluorocarbon is decomposed and produces 572 mL of chlorine gas at a pressure of 754 mm Hg and a temperature of 298 K.What is the percent chlorine (by mass) in the unknown chlorofluorocarbon?
When CO2(g) is put in a sealed container at 716 K and a pressure of 9.80 atm and is heated to 1386 K , the pressure rises to 23.8 atm . Some of the CO2 decomposes to CO and O2.Calculate the mole percent of CO2 that decomposes.
Baking soda (sodium bicarbonate, NaHCO3) reacts with acids in foods to form carbonic acid (H2CO3), which in turn decomposes to water and carbon dioxide gas. In a cake batter, the CO2(g) forms bubbles and causes the cake to rise.If 1/2 teaspoon of baking soda is indeed completely neutralized by the lactic acid in sour milk, calculate the volume of carbon dioxide gas that would be produced at 1 atm pressure, in an oven set to 360 F.
A 10-liter container is filled with 0.1 mol of H2(g) and heated to 3100 K causing some of the H2(g) to decompose into H(g). The pressure is found to be 3.6 atm .Find the partial pressure of the H(g) that forms from H2 at this temperature. (Assume two significant figures for the temperature.)
Natural gas is very abundant in many Middle Eastern oil fields. However, the costs of shipping the gas to markets in other parts of the world are high because it is necessary to liquefy the gas, which is mainly methane and thus has a boiling point at atmospheric pressure of -164 oC. One possible strategy is to oxidize the methane to methanol, CH3OH, which has a boiling point of 65 oC and can therefore be shipped more readily. Suppose that 1.07×1010 ft3 of methane at atmospheric pressure and 25 oC are oxidized to methanol.What volume of methanol is formed if the density of CH3OH is 0.791 g/mL?
A 6.54 g sample of a mixture of magnesium carbonate and calcium carbonate is treated with excess hydrochloric acid. The resulting reaction produces 1.73 L of carbon dioxide gas at 28 oC and 744 torr pressure.Calculate the total number of moles of carbon dioxide that forms from these reactions.
When hydrochloric acid is poured over potassium sulfide, 43.1 mL of hydrogen sulfide gas is produced at a pressure of 754 torr and 25.8 oC.Determine how much potassium sulfide (in grams) reacted.
A mixture of CO(g) and O2 (g) in a 1.2 -L container at 1.1×103 K has a total pressure of 2.4 atm . After some time the total pressure falls to 1.9 atm as the result of the formation of CO2.Find the mass (in grams) of CO2 that forms.
When hydrochloric acid is poured over potassium sulfide, 42.9 mL of hydrogen sulfide gas is produced at a pressure of 752 torr and 25.8 °C. Write an equation for the gas-evolution reaction and determine how much potassium sulfide (in grams) reacted. 
Consider this reaction. CaCO3(s) → CaO(s) + CO2(g)What mass of CaCO3 will produce 8.0 L of CO2, measured at standard temperature and pressure conditions? The molar mass of CaCO3 is 100 g x mol -1. a) 4.5 gb) 12.5 gc) 36 gd) 280 g
The emission of NO2 by fossiI fuel combustion can be prevented by injecting gaseous urea into the combustion mixture. The urea reduces NO (which oxidizes in air to form NO2) according to the reaction: 2 CO(NH2)2(g) + 4 NO(g) + O2(g) → 4 N2(g) + 2 CO2(g) + 4 H2O(g) Suppose that the exhaust stream of an automobile has a flow rate of 2.55 L/s at 655 K and contains a partial pressure of NO of 12.4 torr. What total mass of urea is necessary to react completely with the NO formed during 8.0 hours of driving? 
Consider the chemical reaction:2 KClO3 (s) → 2 KCl (s) + 3 O2 (g). If 245.1 grams of KClO3 reacts completely in a container that is at constant pressure of 1.00 atm and constant temperature of 273 Celsius, what volume of gas in liters is produced? (The molar mass of KClO3 is 122.55 g/mol)44.8 L67.2 L89.6 L112 L134 L
In the synthesis of ammonia gas from nitrogen and hydrogen,N2(g) + 3H2(g) → 2NH3(g)what is the maximum volume, in liters, of NH 3 that can be formed from 15.0 L of H 2.a. 7.50b. 10.0c. 15.0d. 22.5e. 30.0
Determine the theoretical yield of K2CO3 when 0.392 moles of KO2 react with 29.0 L of CO2 (at STP - 0°C, 1 atm). The molar mass of KO 2 = 71.10 g/mol and K2CO3 = 138.21 g/mol. 4 KO2(s) + 2 CO2(g) → 2 K2CO3(s) + 3 O2(g) a) 27.1 gb) 179 gc) 91.7 gd) 206 ge) 61.0 g 
DrRuth says: Combustion means react with oxygen gas, making water and carbon dioxide as products. How much carbon dioxide measured at 25.0°C and 821 Torr would be produced by the combustion of 319 g of glucose (C6H12O6)? 1. 241 L 2. 20.2 L 3. 3.37 L 4. 40.1 L
The chemical reaction N2(g) + 3H2(g) → 2NH3(g) is carried out below:20.0L N2 5.0L H210.0 atm 5.0 atma. When the stopcock between the two reaction vessels is opened, the reaction proceeds. Calculate the partial pressure of NH3 after the reaction is complete. Assume 100% yield for the reaction and that the temperature is constant.b.What will be the effect on the volume of an ideal gas if both the pressure is increased 10 fold and the absolute temperature is doubled?
Calcium carbide (CaC2) reacts with water to produce acetylene (C 2H2) according to the equationCaC2(s)  +  H2O(l) → Ca(OH)(s)  + C2H2(g)A certain mass of CaC2 reacts completely with water to give 64.5 L of C 2H2 at 50.0°C and P = 1.00 atm. If the same mass of CaC2 reacts completely at 400.0°C and P= 2.00 atm, what volume of C2H2 (in L) can be collected at the higher temperature and pressure?a) none of the given answersb) 516c) 0.015d) 67.2e) 258
In the past, acetylene C2H2 was produced by reacting calcium carbide with water according to the following chemical equation: CaC2 + 2 H2O → Ca(OH)2 + C2H2 What would be the volume of acetylene gas produced at 25 o C and 0.950 atm by the reaction of 128 g of calcium carbide and 45.0 g of water? a. 45.2 L b. 39.2 L c. 32.2 L d. 12.2 L e. 49.2 L
Oxygen gas reacts with powdered aluminum according to the following reaction:4Al(s) + 3O2(g) → 2Al2O3(s)What volume of O2 gas (in L), measured at 780 mm Hg and 19°C, is required to completely react with 50.7g of Al?
Baggage handlers at airports routinely screen luggage for the presence of nitroglycerin, C3H5(NO3)3 (Molar mass = 227.11 g). Nitroglycerin is a highly explosive compound and decomposes according to the following equation:4 C3H5(NO3)3(s)  → 12 CO2 (g) + 10 H2O (g) + 6 N2 (g) + O2 (g)Calculate the total volume of CO 2 gas collected at 1.2 atm and 27.0 oC from 42.5 grams of nitroglycerin.a. 12.6 Lb. 0.346 Lc. 1.04 Ld. 3.84 Le. 11.5 L  
Chlorine dioxide gas (ClO2) is used as a commercial bleaching agent. It bleaches materials by oxidizing them. In the course of these reactions, the ClO2 is itself reduced.One method of preparing ClO2 is by the reaction of chlorine and sodium chlorite:Cl2(g) + 2 NaClO2(s) → 2 ClO2(g) + 2 NaCl(s)If you allow 15.5 g of NaClO2 to react with 2.00 L of chlorine gas at a pressure of 1.50 atm at 21 oC, how many grams of  ClO2 can be prepared?
Consider the chemical reaction:C(s) + H2O(g) → CO(g) + H2(g)How many liters of hydrogen gas are formed from the complete reaction of 15.7 g C? Assume that the hydrogen gas is collected at a pressure of 1.0 atm and a temperature of 355 K.   
Consider the chemical reaction:2 H2O(l) →  2H2(g) + O2(g) What mass of H2O is required to form 1.4 L of O2 at a temperature of 315 K and a pressure of 0.957 atm? 
CH3OH can be synthesized by the reaction: CO(g) + 2 H2(g) → CH3OHWhat volume of H2 gas (in L), at 748 mmHg and 86 °C, is required to synthesize 25.8 g CH 3OH? How many liters of CO gas, measured under the same conditions, is required?  
What volume of CO2 gas (MM = 44.01 g/mol) can be produced from the reaction of 2.00 L of 1.00 M HCl reacting with excess CaCO3 at standard temperature and pressure?  2 HCl (aq) + CaCO3 (s) → CO2 (g) + H2O(l) + CaCl2 (aq)A.  0.509 L        B.  2.00 L        C.  4.00 L        D.  22.4 L        E.  44.8 L
At 477 K and 645 mmHg, what volume of N2 will react completely with 29.2 L H 2 to produce NH3? a. 24.4 L b. 12.2 L c. 7.40 L d. 9.7 L
Ethene is converted to ethane by the reactionC2H4(g) + H2(g)   C2H6(g)C2H4 flows into a catalytic reactor at 25.0 atm and 300.°C with a flow rate of 1000. L/min. Hydrogen at 25.0 atm and 300.°C flows into the reactor at a flow rate of 1500. L/min. If 15.0 kg C2H6 is collected per minute, what is the percent yield of the reaction?
Methanol (CH3OH) can be produced by the following reaction:CO(g) + 2H2(g) → CH3OH(g)Hydrogen at STP flows into a reactor at a rate of 16.0 L/min. Carbon monoxide at STP flows into the reactor at a rate of 25.0 L/min. If 5.30 g methanol is produced per minute, what is the percent yield of the reaction?
Consider the following reaction:2 SO2 (g) + O2(g) → 2 SO3(g)282.8 mL of SO2 is allowed to react with 160.5 mL of O2 (both measured at 316 K and 50.1 mmHg ). If 185.0 mL of SO3 is collected (measured at 316 K and 50.1 mmHg ), what is the percent yield for the reaction?
The nitrogen content of organic compounds can be determined by the Dumas method. The compound in question is first reacted by passage over hot CuO(s):Compound   N2(g) + CO2(g) + H2O(g)The product gas is then passed through a concentrated solution of KOH to remove the CO2. After passage through the KOH solution, the gas contains N2 and is saturated with water vapor. In a given experiment a 0.253-g sample of a compound produced 31.8 mL N2 saturated with water vapor at 25°C and 726 torr. What is the mass percent of nitrogen in the compound? (The vapor pressure of water at 25°C is 23.8 torr.)
At elevated temperatures, sodium chlorate decomposes to produce sodium chloride and oxygen gas. A 0.8765-g sample of impure sodium chlorate was heated until the production of oxygen gas ceased. The oxygen gas collected over water occupied 57.2 mL at a temperature of 22°C and a pressure of 734 torr. Calculate the mass percent of NaClO3 in the original sample. (At 22°C the vapor pressure of water is 19.8 torr.)
An environmental engineer analyzes a sample of air contaminated with sulfur dioxide. To a 500.-mL sample at 700. torr and 38°C, she adds 20.00 mL of 0.01017 M aqueous iodine, which reacts as follows:SO2(g) + I2(aq) + H2O(l) ⟶ HSO4−(aq) + I−(aq) + H+(aq) [unbalanced]Excess I2 reacts with 11.37 mL of 0.0105 M sodium thiosulfate:I2(aq) + S2O32−(aq) ⟶ I−(aq) + S4O62−(aq) [unbalanced]What is the volume % of SO2 in the air sample?
The oxides of Group 2A metals (symbolized by M here) react with carbon dioxide according to the following reaction:MO(s) + CO2(g) → MCO3(s)A 2.85-g sample containing only MgO and CuO is placed in a 3.00-L container. The container is filled with CO2 to a pressure of 740. torr at 20.°C. After the reaction has gone to completion, the pressure inside the flask is 390. torr at 20.°C. What is the mass percent of MgO in the mixture? Assume that only the MgO reacts with CO2.
A 3.90-g sample of a mixture of CaO and BaO is placed in a 1.00-L vessel containing CO2 gas at a pressure of 735 torr and a temperature of 26 oC. The CO2 reacts with the CaO and BaO, forming CaCO3 and BaCO3. When the reaction is complete, the pressure of the remaining CO2 is 155 torr .Calculate the mass percentage of CaO in the mixture.
A catalytic converter in an automobile uses a palladium or platinum catalyst to convert carbon monoxide gas to carbon dioxide according to the following reaction: 2 CO(g) + O2(g) → 2 CO2(g)A chemist researching the effectiveness of a new catalyst combines a 2.0:1.0 mole ratio mixture of carbon monoxide and oxygen gas (respectively) over the catalyst in a 2.45-L flask at a total pressure of 750 torr and a temperature of 552˚C. When the reaction is complete, the pressure in the flask has dropped to 556 torr. What percentage of the carbon monoxide was converted to carbon dioxide?
The combustion of octane, C8H18, proceeds according to the reaction 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (l) If a 6.003ft tank of octane (3.01 lb-mol of octane) combusts, what volume of carbon dioxide is produced at 54.0°F and 14.60 psi?      
The combustion of octane, C8H18, proceeds according to the reaction: 2 C8H18(l) + 25 O2(g) → 16 CO2(g) + 18 H2O(l) If 402 mol of octane combusts, what volume of carbon dioxide is produced at 14.0 °C and 0.995 atm?    
Sulfur dioxide emissions from coal-burning power plants are removed by  flue-gas desulfurization. The flue gas passes through a scrubber, and a slurry of wet calcium carbonate reacts with it to form carbon dioxide and calcium sulfite. The calcium sulfite then reacts with oxygen to form calcium sulfate, which is sold as gypsum. (b) If the mole fraction of oxygen in air is 0.209, what volume (L) of air at 1.00 atm and 25°C is needed to react with all the calcium sulfite?
(a) What is the total volume (in L) of gaseous  products, measured at 350°C and 735 torr, when an automobile engine burns 100. g of C8H18 (a typical component of gasoline)?
If 5.17 g of Ag2O is sealed in a 75.0-mL tube filled with 760 torr of N2 gas at 32˚C, and the tube is heated to 350˚C, the Ag2O decomposes to form oxygen and silver. What is the total pressure inside the tube assuming the volume of the tube remains constant?
Hydrogen cyanide is prepared commercially by the reaction of methane, CH4(g), ammonia, NH3(g), and oxygen, O2(g), at high temperature. The other product is gaseous water.b. What volume of HCN(g) can be obtained from the reaction of 20.0 L CH4(g), 20.0 L NH3(g), and 20.0 L O2(g)? The volumes of all gases are measured at the same temperature and pressure.
When gaseous F2 and solid I2 are heated to high temperatures, the I 2 sublimes and gaseous iodine heptafluoride forms. If 350. torr of F2 and 2.50 g of solid I 2 are put into a 2.50-L container at 250. K and the container is heated to 550. K, what is the final pressure (in torr)? What is the partial pressure of I2 gas?
A 20.0-L stainless steel container at 25°C was charged with 2.00 atm of hydrogen gas and 3.00 atm of oxygen gas. A spark ignited the mixture, producing water. What is the pressure in the tank at 25°C? If the exact same experiment were performed, but the temperature was 125°C instead of 25°C, what would be the pressure in the tank?
(a) What is the total volume (in L) of gaseous products, measured at 350°C and 735 torr, when an automobile engine burns 100. g of C8H18 (a typical component of gasoline)?(b) For part (a), the source of O2 is air, which is 78% N2, 21% O2, and 1.0% Ar by volume. Assuming all the O2 reacts, but no N2 or Ar does, what is the total volume (in L) of the engine’s gaseous exhaust?
Metallic molybdenum can be produced from the mineral molybdenite, MoS2. The mineral is first oxidized in air to molybdenum trioxide and sulfur dioxide. Molybdenum trioxide is then reduced to metallic molybdenum using hydrogen gas. The balanced equations areMoS2(s) + 7/2O2(g) → MoO3(s) + 2SO2(g)MoO3(s) + 3H2(g) → Mo(s) + 3H2O(l)Calculate the volumes of air and hydrogen gas at 17°C and 1.00 atm that are necessary to produce 1.00 x 103 kg pure molybdenum from MoS2. Assume air contains 21% oxygen by volume, and assume 100% yield for each reaction.
Nitric acid is produced commercially by the Ostwald process. In the first step ammonia is oxidized to nitric oxide:4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)Assume this reaction is carried out in the apparatus diagramed below.The stopcock between the two reaction containers is opened, and the reaction proceeds using proper catalysts. Calculate the partial pressure of NO after the reaction is complete. Assume 100% yield for the reaction, assume the final container volume is 3.00 L, and assume the temperature is constant.
Silver oxide decomposes when heated:2 Ag2O(s) → 4 Ag(s) +  O2(g)If 5.76 g of Ag2O is heated and the O2 gas produced by the reaction is collected in an evacuated flask,what is the pressure of the O2 gas if the volume of the flask is 0.65 L and the gas temperature is 25 oC?
Oxygen gas reacts with powdered aluminum according to the following reaction:4 Al(s) + 3 O2(g) → 2 Al2O3(s)What volume of O2 gas, measured at 778 mmHg and 26 oC, is required to completely react with 52.6 g of Al?
The metabolic oxidation of glucose, C6H12O6, in our bodies produces CO2, which is expelled from our lungs as a gas:C6H12O6(aq) + 6 O2(g) → 6 CO2(g) + 6H2O(l)Calculate the volume of dry CO2 produced at body temperature (37 oC) and 0.980 atm when 25.0 g of glucose is consumed in this reaction.
The metabolic oxidation of glucose, C6H12O6, in our bodies produces CO2, which is expelled from our lungs as a gas:C6H12O6 (aq) + 6 O2(g) → 6 CO2(g) + 6H2O(l)Calculate the volume of oxygen you would need, at 1.00 atm and 298 K, to completely oxidize 53 g of glucose.
Ammonium nitrate, a common fertilizer, was used by terrorists in the tragic explosion in Oklahoma City in 1995. How many liters of gas at 307°C and 1.00 atm are formed by the explosive decomposition of 15.0 kg of ammonium nitrate to nitrogen, oxygen, and water vapor?
Small quantities of hydrogen gas can be prepared in the laboratory by the addition of aqueous hydrochloric acid to metallic zinc.Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)Typically, the hydrogen gas is bubbled through water for collection and becomes saturated with water vapor. Suppose 240. mL of hydrogen gas is collected at 30.°C and has a total pressure of 1.032 atm by this process. What is the partial pressure of hydrogen gas in the sample? How many grams of zinc must have reacted to produce this quantity of hydrogen? (The vapor pressure of water is 32 torr at 30°C.)
A baker uses sodium hydrogen carbonate (baking soda) as the leavening agent in a banana-nut quickbread. The baking soda decomposes in either of two possible reactions:(1) 2NaHCO3(s) ⟶Na2CO3(s) + H2O(l) + CO2(g)(2) NaHCO3(s) + H+(aq) ⟶ H2O(l) + CO2(g) + Na+(aq)Calculate the volume (in mL) of CO2 that forms at 200.°C and 0.975 atm per gram of NaHCO 3 by each of the reaction processes.
In the “Méthode Champenoise,” grape juice is fermented in a wine bottle to produce sparkling wine. The reaction isC6H12O6(aq) → 2C2H5OH(aq) + 2CO2(g)Fermentation of 750. mL grape juice (density = 1.0 g/cm3) is allowed to take place in a bottle with a total volume of 825 mL until 12% by volume is ethanol (C2H5OH). Assuming that the CO2 is insoluble in H2O (actually, a wrong assumption), what would be the pressure of CO2 inside the wine bottle at 25°C? (The density of ethanol is 0.79 g/cm3.)
Equal moles of sulfur dioxide gas and oxygen gas are mixed in a flexible reaction vessel and then sparked to initiate the formation of gaseous sulfur trioxide. Assuming that the reaction goes to completion, what is the ratio of the final volume of the gas mixture to the initial volume of the gas mixture if both volumes are measured at the same temperature and pressure?
Canadian chemists have developed a modern variation of the 1899 Mond process for preparing extremely pure metallic nickel. A sample of impure nickel reacts with carbon monoxide at 50°C to form gaseous nickel carbonyl, Ni(CO)4.(a) How many grams of nickel can be converted to the carbonyl with 3.55 m 3 of CO at 100.7 kPa?(b) The carbonyl is then decomposed at 21 atm and 155°C to pure (>99.95%) nickel. How many grams of nickel are obtained per cubic meter of the carbonyl?(c) The released carbon monoxide is cooled and collected for reuse by passing it through water at 35°C. If the barometric pressure is 769 torr, what volume (in m3) of CO is formed per cubic meter of carbonyl?
A gaseous organic compound containing only carbon, hydrogen, and nitrogen is burned in oxygen gas, and the volume of each reactant and product is measured under the same conditions of temperature and pressure. Reaction of four volumes of the compound produces four volumes of CO2, two volumes of N2, and ten volumes of water vapor. (a) How many volumes of O2 were required?
Joseph Priestley first prepared pure oxygen by heating mercuric oxide, HgO:2 HgO(s) ⟶ 2 Hg(l) + O2 (g) (a) Outline the steps necessary to answer the following question: What volume of O2 at 23 °C and 0.975 atm is produced by the decomposition of 5.36 g of HgO?(b) Answer the question.
Consider the following chemical equation.2NO2(g) → N2O4(g)If 25.0 mL NO2 gas is completely converted to N2O4 gas under the same conditions, what volume will the N2O4 occupy?
Consider the following chemical reaction: C(s) + H2O(g) → CO(g) + H2(g). How many liters of hydrogen gas is formed from the complete reaction of 16.6 g C? Assume that the hydrogen gas is collected at a pressure of 1.0 atm and a temperature of 360 K .
CH3OH can be synthesized by the following reaction.CO(g) + 2 H2(g) → CH3OH(g)What volume of H2 gas (in L), measured at 750 mm Hg and 88 oC, is required to synthesize 26.0 g CH3OH?
CH3OH can be synthesized by the following reaction.CO(g) + 2 H2(g) → CH3OH(g)How many liters of CO gas, measured under the same conditions, is required?
During World War II, a portable source of hydrogen gas was needed for weather balloons, and solid metal hydrides were the most convenient form. Many metal hydrides react with water to generate the metal hydroxide and hydrogen. Two candidates were lithium hydride and magnesium hydride. What volume (in L) of gas is formed from 1.00 lb of each hydride reacting with excess water at 750. torr and 27°C?
A large portion of metabolic energy arises from the biological combustion of glucose:C6H12O6(s) + 6O2(g) ⟶ 6CO2(g) + 6H2O(g)(a) If this reaction is carried out in an expandable container at 37°C and 780. torr, what volume of CO2 is produced from 20.0 g of glucose and excess O 2?
During a recent winter month in Sheboygan, Wisconsin, it was necessary to obtain 3500 kWh of heat provided by a natural gas furnace with 89% efficiency to keep a small house warm (the efficiency of a gas furnace is the percent of the heat produced by combustion that is transferred into the house).(a) Assume that natural gas is pure methane and determine the volume of natural gas in cubic feet that was required to heat the house. The average temperature of the natural gas was 56 °F; at this temperature and a pressure of 1 atm, natural gas has a density of 0.681 g/L.(b) How many gallons of LPG (liquefied petroleum gas) would be required to replace the natural gas used? Assume the LPG is liquid propane [C3H8: density, 0.5318 g/mL; enthalpy of combustion, 2219 kJ/mol for the formation of CO2(g) and H2O(l)] and the furnace used to burn the LPG has the same efficiency as the gas furnace(e) What volume of air is required to provide the oxygen for the combustion of the methane used to heat the house? Air contains 23% oxygen by mass. The average density of air during the month was 1.22 g/L.
A large portion of metabolic energy arises from the biological combustion of glucose:C6H12O6(s) + 6O2(g) ⟶ 6CO2(g) + 6H2O(g)(a) If this reaction is carried out in an expandable container at 37°C and 780. torr, what volume of CO2 is produced from 20.0 g of glucose and excess O2?(b) If the reaction is carried out at the same conditions with the stoichiometric amount of O  2, what is the partial pressure of each gas when the reaction is 50% complete (10.0 g of glucose remains)?
The following reaction occurs in a closed container:A(g) + 2 B(g) → 2 C(g)A reaction mixture initially contains 1.6 L of A and 2.1 L of B.Assuming that the volume and temperature of the reaction mixture remain constant, what is the percent change in pressure if the reaction goes to completion?
One way to prevent emission of the pollutant NO from industrial plants is by a catalyzed reaction with NH3:                                        catalyst4NH3(g) + 4NO(g) + O2(g)——⟶  4N2(g) + 6H2O(g)(a) If the NO has a partial pressure of 4.5×10−5 atm in the flue gas, how many liters of NH3 are needed per liter of flue gas at 1.00 atm? 
Nitrogen dioxide is used industrially to produce nitric acid, but it contributes to acid rain and photochemical smog. What volume (in L) of nitrogen dioxide is formed at 735 torr and 28.2°C by reacting 4.95 cm3 of copper (d = 8.95 g/cm3) with 230.0 mL of nitric acid (d = 1.42 g/cm3, 68.0% HNO3 by mass)?Cu(s) + 4HNO3(aq) ⟶Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)
Ammonium carbonate decomposes upon heating according to the following balanced equation: (NH4)2CO3(s) → 2 NH3(g) + CO2(g) + H2O(g). Calculate the total volume of gas produced at 23.0˚C and 1.03 atm by the complete decomposition of 11.9 g of ammonium carbonate.
Ammonium nitrate decomposes explosively upon heating according to the following balanced equation: 2 NH4NO3(s) → 2 N2(g) + O2(g) + 4 H2O(g). Calculate the total volume of gas (at 126˚C and 751 mmHg) produced by the complete decomposition of 1.56 kg of ammonium nitrate.
Gaseous ammonia can be injected into the exhaust stream of a coal-burning power plant to reduce the pollutant NO to N2 according to the following reaction:4 NH3(g) + 4 NO(g) + O2(g) → 4 N2(g) + 6 H2O(g)Suppose that the exhaust stream of a power plant has a flow rate of 335 L/s at a temperature of 955 K, and that the exhaust contains a partial pressure of NO of 22.6 torr .What should be the flow rate of ammonia delivered at 760 torr and 298 K into the stream to react completely with the NO if the ammonia is 65.2% pure (by volume)?
Combustible vapor-air mixtures are flammable over a limited range of concentrations. The minimum volume % of vapor that gives a combustible mixture is called the lower flammable limit (LFL). Generally, the LFL is about half the stoichiometric mixture, which is the concentration required for complete combustion of the vapor in air. (a) If oxygen is 20.9 vol % of air, estimate the LFL for n-hexane, C 6H14. 
The emission of NO2 by fossil fuel combustion can be prevented by injecting gaseous urea into the combustion mixture. The urea reduces NO (which oxidizes in air to form NO2) according to the following reaction:2 CO(NH2)2(g) + 4 NO(g) + O2(g) → 4 N2(g) + 2 CO2(g) + 4 H2O(g)Suppose that the exhaust stream of an automobile has a flow rate of 2.51 L/s at 653 K and contains a partial pressure of NO of 12.1 torr. What total mass of urea is necessary to react completely with the NO formed during 8.1 hours of driving?
Gaseous iodine pentafluoride, IF5, can be prepared by the reaction of solid iodine and gaseous fluorine:I2 (s) + 5 F2(g) → 2 IF5 (g)A 5.10-L flask containing 10.2 g I2 is charged with 10.2 g F2, and the reaction proceeds until one of the reagents is completely consumed. After the reaction is complete, the temperature in the flask is 125oC.What is the partial pressure of IF5 in the flask?
In a bromine-producing plant, how many liters of gaseous elemental bromine at 300°C and 0.855 atm are formed by the reaction of 275 g of sodium bromide and 175.6 g of sodium bromate in aqueous acid solution? (Assume that no Br2 dissolves.)5NaBr(aq) + NaBrO3(aq) + 3H 2SO4(aq) ⟶ 3Br2(g) + 3Na 2SO4(aq) + 3H2O(g)
The chlorofluorocarbon CCl2F2 can be recycled into a different compound by reaction with hydrogen to produce CH2F2(g), a compound useful in chemical manufacturing:CCl2F2 (g) + 4 H2 (g) ⟶ CH2F2 (g) + 2 HCl(g) (a) Outline the steps necessary to answer the following question: What volume of hydrogen at 225 atm and 35.5 °C would be required to react with 1 ton (1.000 × 103 kg) of CCl2F2?(b) Answer the question.
A mixture of NH3(g) and N2H4(g) is placed in a sealed container at 320 K . The total pressure is 0.49 atm . The container is heated to 1200 K at which time both substances decompose completely according to the equations 2 NH3(g) → N2(g) + 3 H2(g); N2H4(g) → N2(g) + 2 H2(g). After decomposition is complete the total pressure at 1200 K is found to be 4.5 atm.Find the percent (by volume) of N2H4(g) in the original mixture. (Assume two significant figures for the temperature.)
Automobile air bags are inflated with nitrogen gas, which is formed by the decomposition of solid sodium azide (NaN3). The other product is sodium metal. Calculate the volume of nitrogen gas at 27 °C and 756 torr formed by the decomposition of 125 g of sodium azide.
The atmosphere slowly oxidizes hydrocarbons in a number of steps that eventually convert the hydrocarbon into carbon dioxide and water. The overall reactions of a number of such steps for methane gas is as follows:CH4(g) + 5 O2(g) + 5 NO(g) → CO2(g) + H2O(g) + 5 NO2(g) + 2 OH(g)Suppose that an atmospheric chemist combines 160 mL of methane at STP, 880 mL of oxygen at STP, and 57.5 mL of NO at STP in a 2.2-L flask. The reaction is allowed to stand for several weeks at 275 K. If the reaction reaches 92.0% of completion (92.0% of the limiting reactant is consumed), what are the partial pressures of each of the reactants in the flask at 275 K?
The atmosphere slowly oxidizes hydrocarbons in a number of steps that eventually convert the hydrocarbon into carbon dioxide and water. The overall reactions of a number of such steps for methane gas is as follows:CH4(g) + 5 O2(g) + 5 NO(g) → CO2(g) + H2O(g) + 5 NO2(g) + 2 OH(g)Suppose that an atmospheric chemist combines 160 mL of methane at STP, 880 mL of oxygen at STP, and 57.5 mL of NO at STP in a 2.2 -L flask. The reaction is allowed to stand for several weeks at 275 K. What is the total pressure in the flask?
Lime, CaO, is produced by heating calcium carbonate, CaCO3; carbon dioxide is the other product. (a) Outline the steps necessary to answer the following question: What volume of carbon dioxide at 875 K and 0.966 atm is produced by the decomposition of 1 ton (1.000 × 103 kg) of calcium carbonate? (b) Answer the question.
The atmosphere slowly oxidizes hydrocarbons in a number of steps that eventually convert the hydrocarbon into carbon dioxide and water. The overall reactions of a number of such steps for methane gas is as follows:CH4(g) + 5 O2(g) + 5 NO(g) → CO2(g) + H2O(g) + 5 NO2(g) + 2 OH(g)Suppose that an atmospheric chemist combines 160 mL of methane at STP, 880 mL of oxygen at STP, and 57.5 mL of NO at STP in a 2.2 -L flask. The reaction is allowed to stand for several weeks at 275 K. If the reaction reaches 92.0% of completion (92.0% of the limiting reactant is consumed), what are the partial pressures of each of the products in the flask at 275 K?
Before small batteries were available, carbide lamps were used for bicycle lights. Acetylene gas, C2H2, and solid calcium hydroxide were formed by the reaction of calcium carbide, CaC2, with water. The ignition of the acetylene gas provided the light. Currently, the same lamps are used by some cavers, and calcium carbide is used to produce acetylene for carbide cannons. (a) Outline the steps necessary to answer the following question: What volume of C2H2 at 1.005 atm and 12.2 °C is formed by the reaction of 15.48 g of CaC2 with water? (b) Answer the question.
Calculate the volume of oxygen required to burn 12.00 L of ethane gas, C2H6, to produce carbon dioxide and water, if the volumes of C2H6 and O2 are measured under the same conditions of temperature and pressure.
“Strike anywhere” matches contain the compound tetraphosphorus trisulfide, which burns to form tetraphosphorus decoxide and sulfur dioxide gas. How many milliliters of sulfur dioxide, measured at 725 torr and 32°C, can be produced from burning 0.800 g of tetraphosphorus trisulfide?
Xenon hexafluoride was one of the first noble gas compounds synthesized. The solid reacts rapidly with the silicon dioxide in glass or quartz containers to form liquid XeOF4 and gaseous silicon tetrafluoride. What is the pressure in a 1.00-L container at 25°C after 2.00 g of xenon hexafluoride reacts? (Assume that silicon tetrafluoride is the only gas present and that it occupies the entire volume.)
In one of his most critical studies on the nature of combustion, Lavoisier heated mercury(II) oxide and isolatede elemental mercury and oxygen gas. If 40.0 g of mercury(II) oxide is heated in a 502-mL vessel and 20.0% (by mass) decomposes, what is the pressure (in atm) of the oxygen that forms at 25.0°C? (Assume that the gas occupies the entire volume)
When 15.0 g of fluorite (CaF2) reacts with excess sulfuric acid, hydrogen fluoride gas is collected at 744 torr and 25.5°C. Solid calcium sulfate is the other product. What gas temperature is required to store the gas in an 8.63-L container at 875 torr?
Which of the following statements describes how the volume of the container changes due to the reaction?Imagine that the reaction 2 CO(g)+O2(g) → 2 CO2(g) occurs in a container that has a piston that moves to maintain a constant pressure when the reaction occurs at constant temperature. Which of the following statements describes how the volume of the container changes due to the reaction: (a) the volume increases by 50%(b) the volume increases by 33%(c) the volume remains constant(d) the volume decreases by 33%(e) the volume decreases by 50%
What volume of oxygen at 423.0 K and a pressure of 127.4 kPa is produced by the decomposition of 129.7 g of BaO2 to BaO and O2?
Aluminum reacts with chlorine gas to form aluminum chloride.2 Al(s) + 3 Cl2(g) → 2 AlCl3(s)What minimum volume of chlorine gas (at 298 K and 251 mmHg ) is required to completely react with 8.01 g of aluminum?
Consider the generic reaction: 2A(g)+B(g) → 2C(g) .If a flask initially contains 1.6 atm of A and 1.6 atm of B, what will be the pressure in the flask if the reaction proceeds to completion? (Assume constant volume and temperature.)
Sulfur trioxide, SO3, is produced in enormous quantities each year for use in the synthesis of sulfuric acid.S(s) + O2(g) → SO2(g)2SO2(g) + O2(g) → 2SO3(g)What volume of O2(g) at 350.°C and a pressure of 5.25 atm is needed to completely convert 5.00 g sulfur to sulfur trioxide?
Nitrogen and hydrogen gases react to form ammonia gas via the following reaction:N2(g) + 3H2(g) → 2NH3(g)At a certain temperature and pressure, 1.6 L of N2 reacts with 4.8 L of H2.If all the N2 and H2 are consumed, what volume of NH3, at the same temperature and pressure, will be produced?
Consider the reaction between 50.0 mL liquid methanol, CH 3OH (density = 0.850 g/mL), and 22.8 L O2 at 27°C and a pressure of 2.00 atm. The products of the reaction are CO 2(g) and H2O(g). Calculate the number of moles of H2O formed if the reaction goes to completion.
One molecule of hemoglobin will combine with four molecules of oxygen. If 1.0 g of hemoglobin combines with 1.53 mL of oxygen at body temperature (37 °C) and a pressure of 743 torr, what is the molar mass of hemoglobin?
Urea (H2NCONH2) is used extensively as a nitrogen source in fertilizers. It is produced commercially from the reaction of ammonia and carbon dioxide:2NH3(g) + CO2(g)  H2NCONH2(s) + H2O(g)Ammonia gas at 223°C and 90. atm flows into a reactor at a rate of 500. L/min. Carbon dioxide at 223°C and 45 atm flows into the reactor at a rate of 600. L/min. What mass of urea is produced per minute by this reaction assuming 100% yield?
An atmospheric chemist studying the pollutant SO2 places a mixture of SO2 and O2 in a 2.00-L container at 800. K and 1.90 atm. When the reaction occurs, gaseous SO3 forms, and the pressure falls to 1.65 atm. How many moles of SO3 form?
Consider the following chemical reaction:2 H2O(l) → 2 H2(g) + O2(g)What mass of H2 O is required to form 1.5 L of O2 at a temperature of 320 K and a pressure of 0.950 atm ?
Both Jacques Charles and Joseph Louis Guy-Lussac were avid balloonists. In his original flight in 1783, Jacques Charles used a balloon that contained approximately 31200 L of H2. He generated the H2 using the reaction between iron and hydrochloric acid:Fe(s) + 2 HCl(aq) → FeCl2(aq) + H2(g)How many kilograms of iron were needed to produce this volume of H2 if the temperature was 24 oC? (For simplicity, assume that the pressure experienced by the balloon will be 1.00 atm.)
In the reaction shown here, 4.55 L of O2 was formed at P = 746 mmHg and T = 308 K .2Ag2O(s) → 4Ag(s)+O2(g)How many grams of Ag2O decomposed?
Xenon and fluorine will react to form binary compounds when a mixture of these two gases is heated to 400°C in a nickel reaction vessel. A 100.0-mL nickel container is filled with xenon and fluorine, giving partial pressures of 1.24 atm and 10.10 atm, respectively, at a temperature of 25°C. The reaction vessel is heated to 400°C to cause a reaction to occur and then cooled to a temperature at which F2 is a gas and the xenon fluoride compound produced is a nonvolatile solid. The remaining F2 gas is transferred to another 100.0-mL nickel container, where the pressure of F2 at 25°C is 7.62 atm. Assuming all of the xenon has reacted, what is the formula of the product?
Hemoglobin is the protein that transports O2 through the blood from the lungs to the rest of the body. To do so, each molecule of hemoglobin combines with four molecules of O2. If 1.00 g of hemoglobin combines with 1.53 mL of O2 at 37°C and 743 torr, what is the molar mass of hemoglobin?
Canadian chemists have developed a modern variation of the 1899 Mond process for preparing extremely pure metallic nickel. A sample of impure nickel reacts with carbon monoxide at 50°C to form gaseous nickel carbonyl, Ni(CO)4.(a) How many grams of nickel can be converted to the carbonyl with 3.55 m 3 of CO at 100.7 kPa?
A 20.0-L nickel container was charged with 0.859 atm of xenon gas and 1.37 atm of fluorine gas at 400°C. The xenon and fluorine react to form xenon tetrafluoride. What mass of xenon tetrafluoride can be produced assuming 100% yield?
Canadian chemists have developed a modern variation of the 1899 Mond process for preparing extremely pure metallic nickel. A sample of impure nickel reacts with carbon monoxide at 50°C to form gaseous nickel carbonyl, Ni(CO)4.(a) How many grams of nickel can be converted to the carbonyl with 3.55 m 3 of CO at 100.7 kPa?(b) The carbonyl is then decomposed at 21 atm and 155°C to pure (>99.95%) nickel. How many grams of nickel are obtained per cubic meter of the carbonyl?
Assume that a single cylinder of an automobile engine has a volume of 525 cm3. How many grams of C8H18 could be combusted by this quantity of O2, assuming complete combustion with formation of CO2 and H2O?
A 3.90-g sample of a mixture of CaO and BaO is placed in a 1.00-L vessel containing CO2 gas at a pressure of 735 torr and a temperature of 26 oC. The CO2 reacts with the CaO and BaO, forming CaCO3 and BaCO3. When the reaction is complete, the pressure of the remaining CO2 is 155 torr .Calculate the number of moles of CO2 that have reacted.
A gaseous organic compound containing only carbon, hydrogen, and nitrogen is burned in oxygen gas, and the volume of each reactant and product is measured under the same conditions of temperature and pressure. Reaction of four volumes of the compound produces four volumes of CO2, two volumes of N2, and ten volumes of water vapor. (b) What is the empirical formula of the compound?
Aqueous sulfurous acid (H2SO3) was made by dissolving 0.200 L of sulfur dioxide gas at 19°C and 745 mmHg in water to yield 500.0 mL of solution. The acid solution required 10.0 mL of sodium hydroxide solution to reach the titration end point. What was the molarity of the sodium hydroxide solution?
A gaseous fuel mixture stored at 748 mmHg and 298 K contains only methane (CH4) and propane (C3H8). When 12.1 L of this fuel mixture is burned, it produces 771 kJ of heat. What is the mole fraction of methane in the mixture? (Assume that the water produced by the combustion is in the gaseous state.)
Chlorine gas reacts with fluorine gas to form chlorine trifluoride.Cl2(g) + 3F2(g) → 2ClF3(g)A 2.05 L reaction vessel, initially at 298 K, contains chlorine gas at a partial pressure of 337 mmHg and fluorine gas at a partial pressure of 801 mmHg .Identify the limiting reactant and determine the theoretical yield of ClF3 in grams.
Carbon monoxide gas reacts with hydrogen gas to form methanol via the following reaction:CO(g) + 2 H2(g) → CH3OH(g)A 1.55 L reaction vessel, initially at 305 K, contains carbon monoxide gas at a partial pressure of 232 mmHg and hydrogen gas at a partial pressure of 376 mmHg .Identify the limiting reactant and determine the theoretical yield of methanol in grams.
In the following reaction, what mass of Ag2O(s) (in grams) is required to form 384 mL of oxygen gas at P = 736 mmHg and 25.0 oC?2Ag2O(s) → 4Ag(s)+O2(g)
A person inhales air richer in O2 and exhales air richer in CO2 and water vapor. During each hour of sleep, a person exhales a total of about 300 L of this CO2-enriched and H2O-enriched air.C6H12O6(s) + 6O2(g) ⟶6CO2(g) + 6H2O(g)(a) If the partial pressures of CO2 and H2O in exhaled air are each 30.0 torr at 37.0°C, calculate the mass (g) of CO2 and of H2O exhaled in 1 h of sleep. (b) How many grams of body mass does the person lose in 8 h of sleep if all the CO  2 and H2O exhaled come from the metabolism of glucose?
Assume that an exhaled breath of air consists of 74.7 % N2, 15.4 % O2, 3.8 % CO2, and 6.1 % water vapor.(a) If the total pressure of the gases is 0.985 atm, calculate the partial pressure of each component of the mixture.(b) If the volume of the exhaled gas is 455 mL and its temperature is 37 °C, calculate the number of moles of CO2 exhaled.(c) How many grams of glucose (C6H12O6) would need to be metabolized to produce this quantity of CO2? (The chemical reaction is the same as that for combustion of C6H12O6. See Section 3.2. in the textbook.)
Consider the following reaction:2 SO2 (g) + O2(g) → 2 SO3(g)If 282.8 mL of SO2 is allowed to react with 160.5 mL of O2 (both measured at 316 K and 50.1 mmHg ), what is the theoretical yield of SO3?
One way to prevent emission of the pollutant NO from industrial plants is by a catalyzed reaction with NH3:                                         catalyst4NH3(g) + 4NO(g) + O2(g)——⟶  4N2(g) + 6H2O(g)(b) If the reaction takes place at 1.00 atm and 365°C, how many grams of NH3 are needed per kiloliter (kL) of flue gas?
Consider the following reaction:2 SO2 (g) + O2(g) → 2 SO3(g)If 282.8 mL of SO2 is allowed to react with 160.5 mL of O2 (both measured at 316 K and 50.1 mmHg ), what is the limiting reactant?
In a certain experiment, magnesium boride (Mg 3B2) reacted with acid to form a mixture of four boron hydrides (BxHy), three as liquids (labeled I, II, and III) and one as a gas (IV).(a) When a 0.1000-g sample of each liquid was transferred to an evacuated 750.0-mL container and volatilized at 70.00°C, sample I had a pressure of 0.05951 atm; sample II, 0.07045 atm; and sample III, 0.05767 atm. What is the molar mass of each liquid?(b) Boron was determined to be 85.63% by mass in sample I, 81.10% in II, and 82.98% in III. What is the molecular formula of each sample?(c) Sample IV was found to be 78.14% boron. The rate of effusion for this gas was compared to that of sulfur dioxide; under identical conditions, 350.0 mL of sample IV effused in 12.00 min and 250.0 mL of sulfur dioxide effused in 13.04 min. What is the molecular formula of sample IV?
Gaseous iodine pentafluoride, IF5, can be prepared by the reaction of solid iodine and gaseous fluorine:I2 (s) + 5 F2(g) → 2 IF5(g)A 5.10-L flask containing 10.2 g I2 is charged with 10.2 g F2, and the reaction proceeds until one of the reagents is completely consumed. After the reaction is complete, the temperature in the flask is 125 oC.What is the total mass of reactants and products in the flask?
Freon-12 (CF2Cl2), widely used as a refrigerant and aerosol propellant, is a dangerous air pollutant. In the troposphere, it traps heat 25 times as effectively as CO2, and in the stratosphere, it participates in the breakdown of ozone. Freon-12 is prepared industrially by reaction of gaseous carbon tetrachloride with hydrogen fluoride. Hydrogen chloride gas also forms. How many grams of carbon tetrachloride are required for the production of 16.0 dm3 of Freon-12 at 27°C and 1.20 atm?
Sulfur dioxide emissions from coal-burning power plants are removed by  flue-gas desulfurization. The flue gas passes through a scrubber, and a slurry of wet calcium carbonate reacts with it to form carbon dioxide and calcium sulfite. The calcium sulfite then reacts with oxygen to form calcium sulfate, which is sold as gypsum. (a) If the sulfur dioxide concentration is 1000 times higher than its mole fraction in clean dry air (2×10−10), how much calcium sulfate (kg) can be made from scrubbing 4 GL of flue gas (1 GL = 1×109 L)? A state-of-the-art scrubber removes at least 95% of the sulfur dioxide. 
In 1897 the Swedish explorer Andreé tried to reach the North Pole in a balloon. The balloon was filled with hydrogen gas. The hydrogen gas was prepared from iron splints and diluted sulfuric acid. The reaction isFe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)The volume of the balloon was 4800 m3 and the loss of hydrogen gas during filling was estimated at 20.%. What mass of iron splints and 98% (by mass) H2SO4 were needed to ensure the complete filling of the balloon? Assume a temperature of 0°C, a pressure of 1.0 atm during filling, and 100% yield.
Calcium hydride, CaH2, reacts with water to form hydrogen gas:CaH2(s) + 2H2O(l) → Ca(OH)2(aq) + 2 H2(g)This reaction is sometimes used to inflate life rafts, weather balloons, and the like, where a simple, compact means of generating H2 is desired.How many grams of CaH2 are needed to generate 146 L of H2 gas if the pressure of H2 is 826 torr at 22 oC?
Chlorine can be prepared in the laboratory by the reaction of manganese dioxide with hydrochloric acid, HCl(aq), as described by the chemical equationMnO2 (s) + 4HCl (aq) → MnCl2 (aq) + 2H2O (l) + Cl2 (g)How much ( in grams)  MnO2(s) should be added to excess HCl(aq) to obtain 145 mL of Cl2(g) at 25°C and 715 Torr?
A 5.00-g sample of solid BaCI2 •2H2O was heated such that the water turned to steam and was driven off. Assuming ideal behavior, what volume would that steam occupy at 1.00 atm and 100.0 C?
The combustion of octane, C6H15, proceeds according to the reaction 2 C8H18 (l) + 25 O2 (g) --> 12CO2 (g) + 18 H2O (l)If 5.70 x 10^2 mol of octane combusts, what volume of carbon dioxide is produced at 36.0 c and 0.995 atm? 
lf 6.00 L of water vapor at 50.2 ºC and 0.121 atm reacts with excess iron, how many grams of iron (Ill) oxide will be produced? 2Fe + 3H2O  →  Fe2O3 + 3H2
In some aquatic ecosystems, nitrate (NO3-) is converted to nitrite (NO2-), which then decomposes to nitrogen and water. As an example of this second reaction, consider the decomposition of ammonium nitrite: NH4NO2 (aq) → N2 (g) + 2H2 O (l) What would be the change in pressure in a sealed 10.0 L vessel due to the formation of N  2 gas when the ammonium nitrite in 2.40 L of 1.340 M NH4NO2 decomposes at 25 °C?
Part AIf 50.0 L of hydrogen chloride gas reacts with 10.0 L of oxygen gas, what is the volume of chlorine gas produced? Assume all gases are at the same temperature and pressure. HCl (g) + O2 (g) → Cl2 (g) + H2O (g) Express your answer with the appropriate units.
The combustion of octane, C8H18, proceeds according to the reaction2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) If 305 mol of octane combusts, what volume of carbon dioxide is produced at 35.0°C and 0.995 atm?
A baker uses sodium hydrogen carbonate (baking soda) as the agent in a banana-nut quickbread. The baking soda decomposes according to two possible reactions. Reaction 1: 2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g) Reaction 2: NaHCO3(s) + H+(aq) → H2O(l) + CO2(g) + Na+(aq) Calculate the volume (in mL) of CO2 that forms at 220 °C and 0.906 atm per gram of NaHCO 3 by each of the reaction processes. 
Enter your answer in the provided box.Xenon hexafluoride was one of the first noble gas compounds synthesized. The solid reacts rapidly with the silicon dioxide in glass or quartz containers to form liquid XeOF4 and gaseous silicon tetrafluoride. What is the pressure in a 0.500-L container at 25°C after 3.05 g of xenon hexafluoride reacts? (Assume that silicon tetrafluoride is the only gas present and that it occupies the entire volume.)
A mixture of oxygen and nitrogen gases is maintained in a 9.63 L flask at a pressure of 137 atm and a temperature of 15 C. If the gas mixture contains 6.66 grams of oxygen, the number of grams of nitrogen in the mixture is g.
How many milliliters of oxygen gas at STP are released from heating 2.90 g of mercuric oxide?2HgO(s) → 2 Hg (l) + O2 (g)Express your answer with the appropriate units.
Calculate the mass in grams of hydrochloride produced when 5.35 L of molecular hydrogen measured at STP reacts with an excess of molecular chlorine gas.H2(g) + Cl2(g) → 2HCl(g) g
A 2.95 - g sample of an unknown chlorofluorocarbon is decomposed and produces 583 mL of chlorine gas at a pressure of 750 mm Hg and a temperature of 298 K. What is the percent chlorine (by mass) in the unknown chlorofluorocarbon?
Consider the following reaction:2SO2(g) + O2(g) → 2SO_s(g)If 285.3 mL of SO2 is allowed to react with 167.3 mL of O2 (both measured al 321 K and 53.2 mmHg), what is the limiting reactant?What is the theoretical yield of SO3?If 174.2 mL of SO3 is collected (measured at 321 K and 53.2 mmHg), what is the percent yield for the reaction?
Assume that a single cylinder of an automobile engine has a volume of 525 cm3. If the cylinder is full of air at 73 ° C and 0.990 atm, how many moles of O2 are present? (The mole fraction of O2 in dry air is 0.2095.) n = _________ molHow many grams of C8H18 could be combusted by this quantity of O2, assuming complete combustion with formation of CO2 and H2O? m = _____________ g
Consider the following reaction. H2 (g) + I2 (s) → 2HI (g) If the cylinder with a movable piston below contains 1 mol H2(g) and 1 mol I2(s), which represents the cylinder after the reaction is complete? 
Chlorine gas reacts with fluorine gas to form chlorine trifluoride. Cl2 (g) + 3F2 (g) → 2ClF3 (g) A 1.95 L reaction vessel, initially at 298 K, contains chlorine gas at a partial pressure of 337 mmHg and fluorine gas at a partial pressure of 797 mmHg. Identify the limiting reactant and determine the theoretical yield of ClF3 in grams. Express your answer with the appropriate units.
Chlorine gas reacts with fluorine gas to form chlorine trifluoride. Cl2 (g) + 3F2 (g) → 2 ClF3 (g) A 2.00 L reaction vessel, initially at 298 K, contains chlorine gas at a partial pressure of 337 mmHg and fluorine gas at a partial pressure of 855 mmHg. What is the pressure of ClF3 in the reaction vessel after the reaction? Express your answer to three significant figures. What is the total pressure in the reaction vessel after the reaction? Express your answer to three significant figures.
The ideal gas law PV = nRT relates pressure P, volume V, temperature T, and number of moles of a gas, n. The gas constant R equals 0.08208 L middot atm/(K • mol) or 8.3145 J/(K • mol). The equation can be rearranged as follows to for n: n = PV/RT This equation is useful when dealing with gaseous because calculations involve mole ratios. Part AWhen heated, calcium carbonate decomposes to yield calcium oxide and carbon dioxide gas via the reaction CaCO3  → CaO + CO2  What is the mass of calcium carbonate needed to produce 63.0 L of carbon dioxide at STP? Express your answer with the appropriate units.
Assume that a single cylinder of an automobile engine has a volume of 524 cm2.Part AIf the cylinder is full of air at 72 °C and 0.990 atm, how many moles of O2 are present? (The mole fraction of O2 in dry is 0.2095)Part BHow many grams of C8 H18 could be combusted by this quantity of O2, assuming combustion with formation of CO2 and H2O?
Chlorine can be prepared in the laboratory by the reaction of manganese dioxide with hydrochloric acid, HCl(aq), as described by the chemical equation MnO2(s) + 4HCl(aq) → MnCl2(aq) + 2H2O(l) + Cl2(g) How much (grams) MnO2 (s) should be added to excess HCI(aq) to obtain 235 ml of Cl2(g) at 25°C and 715 Torr?
Hydrogen and iodine gases react to form hydrogen iodide gas as follows: H2 (g) + I2 (g) → 2HI (g) At a certain temperature and pressure 1.4 L of H 2 reacts with 1.4 L of I 2. If all the H2 and I2 are consumed, what volume of HI, at the same temperature and pressure, will be produced?
Automobile air bags inflate during a crash or sudden stop by the rapid generation of nitrogen gas from sodium azide, according to the reaction:2NaN3 (s) → 2Na(s) + 3N2 (g)How many grams of sodium azide are needed to provide sufficient nitrogen gas to fill a 40.0 x 40.0 x 25.0 cm bag to a pressure of 1.19 atm at 23.0°C?
Enter your answer in the provided box. Ammonium nitrate, a common fertilizer, is used as an explosive in fireworks and by terrorists. It was the material used in the tragic explosion at the Oklahoma City federal building in 1995. How many liters of gas at 307°C and 1.00 atm are formed by the explosive decomposition of 20.7 kg of ammonium nitrate to nitrogen, oxygen, and water vapor? 
Three moles of glyceryl trioleate (triolein) are completely hydrogenated. How many moles of hydrogen are required?
Lithium reacts with nitrogen gas according to the following reaction: 6Li(s)+ N2 (g) → 2Li3N(s) What mass of lithium is required to react completely with 58.6 mL of N2 gas at STP?Express your answer in grams.
Chlorine gas is collected from the following reaction of MnO2(s) with HCl:MnO2(s) + 4HCl(aq) → MnCl2(aq) + Cl2(g) + 2H2O(l) Calculate the volume of HCl solution (1.0 M) needed to produce 5.0 x 103 mL of Cl2 at 1.0 atm and 300K. a. 203 mL b. 51 mL c. 812 mL d. 102 mL e. none of the above
What is the total volume of all gases that are produced when 32.0 mL of C3H5(NO3)3 reacts as shown in the reaction below. Assume standard temp and pressure. (d = 1.60 g/mL, molar mass 227.10 g/mol) 4C3H5(NO3)3 (I) → 6N2(g) + O2(g) + 12CO2(g) + 10H2 (g). 
When aluminum is placed in concentrated hydrochloric acid, hydrogen gas is produced. 2AI (s) + 6HCI(aq) → 2AICI3(aq) + 3H3(g) What volume of H2(g) is produced when 5.40 g of Al(s) reacts at STP?
Ammonium carbonate decomposes upon heating according to the following balanced equation: (NH4)2CO3 (s) → 2 NH3 (g) + CO2 (g) + H2O (g) Calculate the total volume of gas produced at 20.0°C and 1.03 atm by the complete decomposition of 11.8 g of ammonium carbonate.
Oxygen gas reacts with powdered aluminum according to the following reaction: 4Al (s) + 3O2 (g) → 2Al2O3 (s) What volume of O2 gas (in L) measured at 795 mmHg and 27°C, is required to completely react with 53.5 g of Al? 
Chlorine can be prepared in the laboratory by the reaction of manganese dioxide with hydrochloric acid, HCl(aq), as described by the chemical equation MnO2 (s) + 4HCl (aq) → MnCl2 (aq) + 2 H2O (l) + Cl2 (g) How much MnO2(s) should be added to excess HCl(aq) to obtain 225 mL of Cl2(g) at 25° and 715 Torr?
Limestone (CaCO3) reacts with hydrochloric acid according to the equation: CaCO 3 + 2HCl → CaCl2 + H2O + CO2 If 1.00 mol of CO2 has a volume of 22.4 L under the reaction conditions, how many liters of gas can be formed by reaction of 2.30 g of CaCO3 with 2.30 g of HCl? Which reactant is limiting? a. limestoneb. hydrochloric acid 
How many grams of carbon disulfide are needed to completely consume 53.3 L of chlorine gas according to the following reaction at 25°C and 1 atm? carbon disulfide (s) + chlorine (g) → carbon tetrachloride (l) + sulfur dichloride (s) 
For each of these equations, determine the change in the number of moles of gas, Δngas. (a) (NH4)2CO3 (s) → 2NH3 (g) + CO2 (g) + H2O (g) (b) H2 (g) + Cl2 (g) → 2HCl (g) (c) 2H2 (g) + O2 (g) → 2 H2O(l) (d) 2Na (s) + Cl2 (g) → 2NaCl (s)
Potassium chlorate (KClO3 molar mass 122.5 g/mol) decomposes into oxygen gas and potassium chloride. When 3.25 grams of potassium chlorate decomposes at 610 torr and 34oC, what is the volume of oxygen gas produced? Remember to convert torr to atm and Celsius to Kelvin.2KClO3 (s) → 3O2(g) + 2KCl (s).
The combustion of octane, C8H18, proceeds according to the reaction 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (l)lf 546 mol of octane combusts, what volume of carbon dioxide is produced at 16 0°C and 0.935 atm?
The combustion of octane, C8H18 proceeds according to the reaction 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (l) If 313 mol of octane combusts, what volume of carbon dioxide is produced at 39.0°C and 0.995 atm?
When aluminum is placed in concentrated hydrochloric acid, hydrogen gas is produced. 2 Al (s) + 6HCl (aq) → 2 AICI3 (aq) + 3H2 (g) What volume of H2 (g) is produced when 8.40 g of Al (s) reacts at STP?
When aluminum is placed in concentrated hydrochloric acid, hydrogen gas is produced. 2AI (s) + 6HCl (aq) → 2AICl3 (aq) + 3H2 (g) What volume of H2(g) is produced when 7.10 g of Al(s) reacts at STP? 
Oxygen gas reacts with powdered aluminum according to the following reaction 4Al(s) + 3O2(g) → 2Al2O3(s)What volume of O2 gas, measured at 765 mmHg and 22°C, is required to completely react with 53.0 g of Al? Express the volume in liters to three significant figures. 
The total volume of hydrogen gas needed to fill the Hinderburg was 2.00 x 108 L at 1.00 atm and 25.0°C. How much energy was evolved when it burned?Hint-Use the Ideal Gas Law to obtain the moles of hydrogen gas. 2H2 (g) + O2 (g) → 2H2O (l)      ΔH = -572 kJa. 2.86 x 104 kJb. 5.72 x 1010 kJc. 8.18 x 106 kJd. 35 x 1011 kJ e. 2.34 x 109 kJ
Part AWhat is the volume occupied by 14.1 g of argon gas at a pressure of 1.20 atm and a temperature of 400 K? Express your answer with the appropriate units. Part B Compare the volume of 14.1 g of helium to 14.1 g of argon gas (under identical conditions).                       • The volume would be the same for helium gas.                          • The volume would be greater for helium gas.                        • The volume would be lower for helium gas. 
Part AWhat volume of O2 at 836 mmHg and 41°C is required to synthesize 13.5 mol of NO? Express your answer numerically in liters.
The combustion of octane, C8H18, proceeds according to the reaction 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (l) If 579 mol of octane combusts, what volume of carbon dioxide is produced at 34.0°C and 0.995 atm?
When ammonium nitrite (NH4NO2) is heated, it decomposes to give nitrogen gas.a) Write a balanced equation for this reaction andb) Calculate the quantity (in gram) of NH4NO2 needed to inflate a balloon to a volume of 86.2 mL at 1.20 atm and 22 °C.
Imagine that you have a 5.50 L gas tank and a 4.50 L gas tank. You need to fill one tank with oxygen and the other with acetylene to use in conjunction with your welding torch. If you fill the larger tank with oxygen to a pressure of 145 atm, to what pressure should you fill the acetylene tank to ensure that you run out of each gas at the same time? Assume ideal behavior for all gases.2C2H2 (g) + 5O2 (g) → 4CO2 (g) + 2 H2O (g)
Ammonium nitrite, NH4NO2, will decompose to yield nitrogen gas and water vapor by the following equation:NH4NO2 (s) → 2H2O (g) + N2 (g)A sample of 25.0g NH4NO2 was heated at 100 °C in a 10.0 L reaction vessel until all the NH  4NO2 had decomposed and H2O and N2 had formed.At the end of the reactiona) what is the total pressure in the reaction vessel?b) what is the partial pressure of N2?c) If the volume of the reaction vessel is decreased to 5.0 L, would you expect the pressure of the gases to increase or decrease?
Some very effective rocket fuels are composed of lightweight liquids. The fuel composed of dimethylhydrazine [(CH3)2N2H2] mixed with dinitrogen tetroxide was used to power the Lunar Lander in its missions to the moon. The two components react according to the following equation:(CH3)2N2H2(l) + 2N2O4(l) → 3N2(g) + 4H2O(g) + 2CO2(g)If 150 g dimethylhydrazine reacts with excess dinitrogen tetroxide and the product gases are collected at 127°C in an evacuated 250-L tank, what is the partial pressure of nitrogen gas produced and what is the total pressure in the tank assuming the reaction has 100% yield?
Reaction vessel contains 6.1 g of CO and 6.1 g of O2. How many grams of CO2 could be produced according to the following reaction?2 CO + O2 → 2 CO2
A miniature volcano can be made in the laboratory with ammonium dichromate. When ignited, it decomposes in a fiery display. (NH4)2Cr2O7 (s) → N2 (g) + 4H2O (g) + Cr2O3 (s) If 0.76 g of ammonium dichromate is used, and the gases from this reaction are trapped in a 15.1 L flask at 29°C, what is the total pressure of the gas in the flask? What are the partial pressures of N2 and H2O? 
Chlorine gas reacts with fluorine gas to form chlorine trifluoride. Cl2 (g) + 3F2 (g) → 2CIF3 (g) A 2.05 L reaction vessel, initially at 298 K, contain chlorine gas at a partial pressure of 337 mmHg and fluorine gas at a partial pressure of 811 mmHg.Identify the limiting reactant and determine the theoretical yield of CIF3 in grams. Express your answer with the appropriate units. 
A 15.0-L rigid container was charged with 0.500 atm of krypton gas and 1.50 atm of chlorine gas at 350.°C. The krypton and chlorine react to form krypton tetrachloride. What mass of krypton tetrachloride can be produced assuming 100% yield?
Ozone is depleted in the stratosphere by chlorine from CF3Cl according to the following set of equations:CF3Cl + UV light → CF3 + ClCl + O3 → ClO + O2O3 + UV light → O2 + OClO + O → Cl + O2What total volume of ozone measured at a pressure of 25.5 mmHg and a temperature of 226 K can be destroyed when all of the chlorine from 15.5 g of CF3Cl goes through ten cycles of the above reactions?
Ammonia, NH3(g), and hydrogen chloride, HCl(g), react to form solid ammonium chloride, NH4Cl(s):NH3(g) + HCl(g) → NH4Cl(s)Two 2.50 L flasks at 30.0 oC are connected by a stopcock, as shown in the drawingOne flask contains 5.60g NH3(g), and the other contains 4.60 g  HCl(g). When the stopcock is opened, the gases react until one is completely consumed.What will be the final pressure of the system after the reaction is complete? (Neglect the volume of the ammonium chloride formed.)
Hydrogen azide, HN3, decomposes on heating by the following unbalanced equation:HN3(g) → N2(g) + H2(g)If 3.0 atm of pure HN3(g) is decomposed initially, what is the final total pressure in the reaction container? What are the partial pressures of nitrogen and hydrogen gas? Assume the volume and temperature of the reaction container are constant.
Gaseous iodine pentafluoride, IF5, can be prepared by the reaction of solid iodine and gaseous fluorine:I2 (s) + 5 F2(g) → 2 IF5(g)A 5.10-L flask containing 10.2 g I2 is charged with 10.2 g F2, and the reaction proceeds until one of the reagents is completely consumed. After the reaction is complete, the temperature in the flask is 125 oC.What is the mole fraction of IF5 in the flask?
Magnesium can be used as a "getter" in evacuated enclosures to react with the last traces of oxygen. (The magnesium is usually heated by passing an electric current through a wire or ribbon of the metal.) If an enclosure of 0.462 L has a partial pressure of O2 of 3.6 × 10−6 torr at 28oC, what mass of magnesium will react according to the following equation: 2 Mg(s) + O2(g) → 2 MgO(s)?
A 2.747-g sample of manganese metal is reacted with excess HCl gas to produce 3.22 L H2(g) at 373 K and 0.951 atm and a manganese chloride compound (MnClx). What is the formula of the manganese chloride compound produced in the reaction?
Cavendish prepared hydrogen in 1766 by the novel method of passing steam through a red-hot gun barrel:4 H2O (g) + 3 Fe(s) ⟶ Fe3O4 (s) + 4 H2 (g) (a) Outline the steps necessary to answer the following question: What volume of H2 at a pressure of 745 torr and a temperature of 20 °C can be prepared from the reaction of 15.0 g of H2O?
Consider the unbalanced chemical equation below:CaSiO3(s) + HF(g) → CaF2(aq) + SiF4(g) + H2O(l)Suppose a 32.9-g sample of CaSiO3 is reacted with 31.8 L of HF at 27.0°C and 1.00 atm. Assuming the reaction goes to completion, calculate the mass of the SiF4 and H2O produced in the reaction.
Concentrated hydrogen peroxide solutions are explosively decomposed by traces of transition metal ions (such as Mn or Fe):2H2O2(aq) → 2H2O(l) + O2(g)What volume of pure O2(g), collected at 27°C and 746 torr, would be generated by decomposition of 125 g of a 50.0% by mass hydrogen peroxide solution? Ignore any water vapor that may be present.
An important process for the production of acrylonitrile (C3H3N) is given by the following equation:2C3H6(g) + 2NH3(g) + 3O2(g) → 2C3H3N(g) + 6H2O(g)A 150.-L reactor is charged to the following partial pressures at 25°C:What mass of acrylonitrile can be produced from this mixture (MPa = 10 6 Pa)?
Propane, C3H8, is a hydrocarbon that is commonly used as a fuel.Calculate the volume of air at 25°C and 1.00 atmosphere that is needed to completely combust 25.0 grams of propane. Assume that air is 21.0 percent O2 by volume. (Hint: we will see how to do this calculation in a later chapter on gases—for now use the information that 1.00 L of air at 25°C and 1.00 atm contains 0.275 g of O2 per liter.)