Concept #1:

**Mass** or **weight percent** is the percentage of a given element or compound within a solution.

Example #1:
Calculate the amount of water (in kilograms) that must be added to 12.0 g of urea, (NH_{2})_{2}CO, in the preparation of a 18.3 percent by mass solution. The molar mass of urea, (NH_{2})_{2}CO, is 60.055 g/mol.

Example #2:

A solution was prepared by dissolving 51.0 g of KBr in 310 mL of water. Calculate the mass percent of KBr in the solution.

Practice: At 298 K, a solution is prepared by dissolving 12.7 g NaCl in 95.5 mL of water. What is the ppm of NaCl if the density of water at this temperature is 0.9983 g/mL.

Lead poisoning is a serious condition resulting from the ingestion of lead in food, water, or other environmental sources. It affects the central nervous system, leading to a variety of symptoms such as distractibility, lethargy, and loss of motor coordination. Lead poisoning is treated with chelating agents, substances that bind to metal ions, allowing it to be eliminated in the urine. A modern chelating agent used for this purpose is succimer (C4 H6 O4 S2 ). Suppose you are trying to determine the appropriate dose for succimer treatment of lead poisoning.What minimum mass of succimer (in mg) is needed to bind all of the lead in a patients bloodstream? Assume that patient blood lead levels are 41 g/dL , that total blood volume is 5.0 L, and that one mole of succimer binds one mole of lead.

Commercial aqueous nitric acid has a density of 1.42 g/mL and is 16 M.Calculate the percent HNO3 by mass in the solution.

If we dissolve 25 grams of salt in 251 grams of water, what is the mass of the resulting solution?

Acetonitrile (CH3 CN) is a polar organic solvent that dissolves a wide range of solutes, including many salts. The density of a 1.90 M LiBr solution in acetonitrile is 0.827 g/cm3 .Calculate the concentration of the solution in mass percentage of CH3 CN.

Find the percent by mass of sodium chloride in a 1.30 M NaCl solution. The density of the solution is 1.06 g/mL .

A solution is prepared by mixing together cyclohexane (C 6H12, MW = 84.16 g/mol) and p-xylene (C6H4(CH3)2), MW = 106.17 g/mol). The mole fraction of p-xylene in the solution is X p = 0.1664. What are the molality and the percent by mass p-xylene in the solution?

Determine the percent sulfuric acid by mass of a 1.37 m aqueous solution of H 2SO4.A) 0.1342%B) 11.84%C) 13.42%D) 13.98%E) 1.37%

An aqueous KNO3 solution is made using 87.6 g of KNO3 diluted to a total solution volume of 1.51 L. (Assume a density of 1.05 g/ml for the solution.)Part ACalculate the molarity of the solution.Part BCalculate the molality of the solution.Part CCalculate the mass percent of the solution.

The chemist must prepare 1.00 kg of 15.0% (w/w) acetic acid using a stock solution which is 36.0% (w/w) acetic acid (d = 1.045 g/mL). Which of the following combinations will give her the solution she wants?A) 417 mL of 36% acetic acid in 583 mL of distilled waterB) 417 g of 36% acetic acid in 583 g of distilled waterC) 360 mL of 36% acetic acid in 640 mL of distilled waterD) 360 mL of 36% acetic acid in 640 g of distilled waterE) 150 g of 36% acetic acid in 850 g of distilled water

What is the percent CdSO4 by mass in a 1.0 molal aqueous CdSO4 solution?A. 0.10 %B. 20.8 %C. 17.2 %D. 24.4 %E. 0.001%

A stock solution of hydrofluoric acid is 15 M and has a density of 0.99 g/mL at 25 °C. What is the mass percent of HF at 25 °C?a. 15%b. 30%c. 45%d. 60%

An aqueous KNO3 solution is made using 70.5g of KNO 3 diluted to a total solution volume of 1.97 L .a. Calculate the molarity of the solution. (assume a density of 1.05 g/mL for the solution)b. Calculate the molality of the solution.c. Calculate the mass percent of the solution.

In lab you need to prepare at least 100 mL of each of the following solutions. Explain how you would proceed using thegiven information. c. 25% NaOH by mass in CH3OH (d = 0.79 g/cm3)

Calculate the percent by mass of KBr in a saturated solution of KBr in water at 10 °C. See Figure 11.17 for useful data, and report the computed percentage to one significant digit.

A solution is prepared by dissolving 28.6 g of glucose (C6H12O6) in 360 g of water. The final volume of the solution is 380 mL. For this solution, calculate each of the following.Percent by mass

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 oC. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g/mL and 1.00 g/mL, respectively. For this solution, calculate each of the following.Percent by mass

Consider this question: What mass of a concentrated solution of nitric acid (68.0% HNO3 by mass) is needed to prepare 400.0 g of a 10.0% solution of HNO3 by mass? (a) Outline the steps necessary to answer the question. (b) Answer the question.

What mass of a 4.00% NaOH solution by mass contains 15.0 g of NaOH?

What mass of solid NaOH (97.0% NaOH by mass) is required to prepare 1.00 L of a 10.0% solution of NaOH by mass? The density of the 10.0% solution is 1.109 g/mL.

What mass of HCl is contained in 45.0 mL of an aqueous HCl solution that has a density of 1.19 g cm–3 and contains 37.21% HCl by mass?

Solutions of hydrogen in palladium may be formed by exposing Pd metal to H2 gas. The concentration of hydrogen in the palladium depends on the pressure of H2 gas applied, but in a more complex fashion than can be described by Henry’s law. Under certain conditions, 0.94 g of hydrogen gas is dissolved in 215 g of palladium metal (solution density = 10.8 g cm3).(c) Determine the percent by mass of hydrogen atoms in this solution.

Eighty proof whiskey is 40% ethanol (C2H5OH) by volume. A man has 7.0 L of blood and drinks 28 mL of the whiskey, of which 22% of the ethanol goes into his blood. (a) What concentration (in g/mL) of ethanol is in his blood (d of ethanol = 0.789 g/mL)?

Eighty proof whiskey is 40% ethanol (C2H5OH) by volume. A man has 7.0 L of blood and drinks 28 mL of the whiskey, of which 22% of the ethanol goes into his blood.(b) What volume (in mL) of whiskey would raise his blood alcohol level to 8.0×10−4 g/mL, the level at which a person is considered intoxicated?

How would you prepare the following aqueous solutions?(b) 1.20 kg of 2.20 mass % HNO3 from 52.0 mass % HNO3

How would you prepare the following aqueous solutions?(a) 1.50 kg of 0.0355 m ethanol (C2H5OH) from ethanol and water

How would you prepare the following aqueous solutions?(b) 445 g of 13.0 mass % HCl from 34.1 mass % HCl

Is 50% by mass of methanol dissolved in ethanol different from 50% by mass of ethanol dissolved in methanol? Explain.

A solution contains 0.35 mol of isopropanol (C3H7OH) dissolved in 0.85 mol of water.(b) The mass percent?

Caffeine (C8H10N4O2) is a stimulant found in coffee and tea. A solution of caffeine in the solvent chloroform (CHCl3) has a concentration of 0.0510
m.Calculate the percentage of caffeine by mass in the solution.

A site in Pennsylvania receives a total annual deposition of 2.688 g/m 2 of sulfate from fertilizer and acid rain. The mass ratio of ammonium sulfate/ammonium bisulfate/sulfuric acid is 3.0/5.5/1.0. (a) How much acid, expressed as kilograms (kg) of sulfuric acid, is deposited over an area of 10. km2?

A site in Pennsylvania receives a total annual deposition of 2.688 g/m 2 of sulfate from fertilizer and acid rain. The mass ratio of ammonium sulfate/ammonium bisulfate/sulfuric acid is 3.0/5.5/1.0. (b) How many pounds of CaCO 3 are needed to neutralize this acid?

A solution contains 0.100 mol of NaCl dissolved in 8.60 mol of water.(b) The mass percent?

An automobile antifreeze mixture is made by mixing equal volumes of ethylene glycol (d = 1.114 g/mL; ℳ = 62.07 g/mol) and water (d = 1.00 g/mL) at 20°C. The density of the mixture is 1.070 g/mL. Express the concentration of ethylene glycol as:(a) Volume percent

An automobile antifreeze mixture is made by mixing equal volumes of ethylene glycol (d = 1.114 g/mL; ℳ = 62.07 g/mol) and water (d = 1.00 g/mL) at 20°C. The density of the mixture is 1.070 g/mL. Express the concentration of ethylene glycol as:(b) Mass percent

In lab you need to prepare at least 100 mL of each of the following solutions. Explain how you would proceed using thegiven information. b. 15% NaOH by mass in water (d = 1.00 g/cm3)

How many moles of each substance are needed to prepare the following solutions? Part A 67.0 mL of 9.5% m/v KCI (MW 74.55 g/mol)Express your answer using two significant figures. Part B 350.0 mL of 90%m/v acetic acid (Mw 60.06 g/mol) Express your answer using two significant figures.

A student determining the %H2O in CuSO4•5H2O obtains the following data. What is the %H2O in the sample for this experiment?

A 3.56 g sample of a laboratory solution contains 1.97 g of acid. What is the concentration of the solution as a mass percentage?

Part AA hydrocarbon is a compound that contains mostly carbon and hydrogen. Calculate the percent composition (by mass) of the following hydrocarbon: C10H22. Enter the percentages of carbon and hydrogen numerically to four significant figures separated by commas.

Hydrochloric acid is usually purchased in a concentrated from that is 37.0%. HCl by mass and has a density of 1.20 g/mL. Part A How much concentrated solution would you take to prepare 2.85 L of 0.420 M HCl by using with water?

How many grams of Al(NO3)3 are present in 58.9 g of a(n) 12.4% by mass Al(NO3)3 (aq) solution? Enter only a numerical answer. Do not include units.

Enter your answer in the provided box. A sample of 5.98 g of naphthalene (C10H8) is dissolved in 73.8 g of benzene (C6H6). Calculate the percent by mass of naphthalene in this solution.

Citric acid (right) is concentrated in citrus fruits and plays a central metabolic role in nearly every animal and plant cell. How many moles of citric acid are in 9.84 qt of lemon juice (d = 1.09 g/mL) that is 7.61% citric acid by mass?

For a plant food labeled 23-19-17, calculate: Your answer should be in two significant figures. a % nitrogen b. % phosphorus c. % potassium Calculate % sulfate (SO4) in CuSO4. Your answer should be in one significant figure.

A chemist mixes 87. g of acetone with 93. g of 1-bromobutane and 94. g of thiophene. Calculate the percent by mass of each component of this solution. Be sure each of your answer entries has the correct number of significant digits.

If a buffer solution is 0.270 M in a weak acid (Ka = 1.8 x 10-6) and 0.430 M in its conjugate base, what is the pH?

Isopropyl alcohol is mixed with water to produce a 31.0% (v/v) alcohol solution. How many milliliters of each component are present in 665 mL of this solution? (Assume that volumes are additive.)

Load is a basic metal that affects the central nervous system. A Pb-water sample contains 0.0011 % Pb by mass.How much of the water (in mL) contains 1.65 mg of Pb? (Assume a density of 1.0 g/mL) Express your answer using two significant figures.

How many grams of Na2CO3 are present in 12.4 mL of a solution that is 39.0% Na2CO3, by mass. The density of the solution is 1.19 g/mL.

You need to dissolve CaCl2 in water to make a mixture that is 36.5% calcium chloride by mass. If the total mass of the mixture is 180.7 g, what masses of CaCl2 and water should be used?

The amount of nitrogen in an organic substance can be determined by an analytical method called the Kjeldahl method, in which all the nitrogen in the organic substance is converted to ammonia. The ammonia, which is a weak base, can be neutralized with hydrochloric acid, as described by the equation NH3(aq) + HCl(aq) → NH4Cl(aq) If 47.0 mL of 0.150 M HCl(aq) is needed to neutralize all the NH3(g) from a 2.25-g sample of organic material, calculate the mass percentage of nitrogen in the sample.

Enter your answer in the provided box.Calculate the mass % of Br in barium perbromate.

Be sure to answer all parts.Calculate the amount of water (in grams) that must be added to each of the following substances to produce the indicated solution. (a) 5.30 g of urea (NH2)2CO in the preparation of a 20.9 percent by mass solution: (b) 34.5 g of MgCl2 in the preparation of a 3.2 percent mass solution:

A particular coal contains 2.55% sulfur by mass. When the coal is burned, it produces SO2 emissions which combine with rainwater to produce sulfuric acid.a. Use the formula of sulfuric acid to calculate the mass percent of S in sulfuric acid.b. Determine how much sulfturic acid (in metric tons) is produced by the combustion of 1.0 metric ton of this coal. (A metric ton is 1000 kg.)

Calculate the percent composition of the following compounds. Write all values to two decimal places.

A solution was prepared by dissolving 32 g of KCl in 225 g of waterCalculate the mass percent of KCl in the solution

You need to dissolve CaCl2 in water to make a mixture that is 35.5% calcium dichloride by mass. If the total mass of the mixture is 719.9 g, what masses of CaCl2 and water should be used?

Table salt, NaCl(s), and sugar, C12H22O11 (s), are accidentally mixed. A 5.50-g sample is burned, and 1.60 g of CO2 (g) is produced. What was the mass percentage of the table salt in the mixture?

An alloy contains 69 g of pure gold and 37 g of pure zinc. What is the percentage of zinc in the alloy? Express your answer to two significant figures and include the appropriate units.

A certain ore is 33.7% nickel by mass. How many kilograms of this ore would you need to dig up to have 60.0 g of nickel?

Be sure to answer all parts.Calculate the amount of water (in grams) that must be added to each of the following substances to produce the indicated solution. (a) 5.70 g of urea (NH2)2 CO in the preparation of a 24.8 percent by mass solution: (b) 33.1 g of MgCl2 in the preparation of a 4.9 percent mass solution:

What is the mass percentage of iodine (I2) in a solution containing 3.0 x 10-2 mol I in 140 g of CCL4? Express your answer using two significant figures.

You wish to prepare 210 grams of 16.2 % FeCl3. You will need ______ grams of iron(III) chloride and _______ mL of water. Assume that the density of water is 1.00 g/ml.

A 4.97 g sample of a laboratory solution contains 1.03 g of acid. What is the concentration of the solution as a mass percentage?

How many grams of NiF2, are there in 191 grams of an aqueous solution that is 6.65 % by weight NiF2.

A sample weighing 3.093 g is a mixture of Fe 2O3 (molar mass = 159.69) and Al 2O3 (molar mass = 101.96). When heat and a stream of H2 gas is applied to the sample, the Fe2O3 reacts to form metallic Fe and H2O(g). The Al2O3 does not react. If the sample residue (the solid species remaining after the reaction) weighs 2.313 g, what is the mass fraction of Fe2O3 in the original sample?

An alloy contains 59 g of pure silver and 20 g of pure copper. What is the percentage silver in the alloy? Express your answer to two significant figures and include the appropriate units.

A 7.91 g sample of an aqueous solution of hydrochloric acid contains an unknown amount of the acid. lf 10.6 mL of 1.55 M sodium hydroxide are required to neutralize the hydrochloric acid, what is the percent by mass of hydrochloric acid in the mixture?

A student is running an experiment in which 70.1 grams of MnSO4 is needed, but the only jar of reagent in the lab is labelled manganese(II) sulfate monohydrate. How many grams of the hydrate must the student weigh out in order to get the desired amount of the anhydrous compound?

A food chemist determines the concentration of acetic acid in a sample of apple vinegar by acid-base titration. The density of the sample is 1.01 g/mL. The titrant is 1.006 M NaOH. The average volume of titrant required to titrate 25.00 mL subsamples of the vinegar is 20.78 mL. What is the concentration of acetic acid in the vinegar? Express your answer the way a food chemist probably would: as percent by mass.

A solution is prepared by dissolving 23.7 g of CaCl 2 in 375 g of water. The density of the resulting solution is 1.05 g/mL. The concentration of CaCl2 is __________ % by mass.a) 0.0632 b) 6.32 c) 6.24 d) 5.94 e) 0.0594

The iron in a 6.655-g sample containing some Fe 2O3 is reduced to Fe2+. The Fe2+ is titrated with 15.67 mL of 0.1517M K2Cr2O7 in an acid solution. 6Fe2+ + Cr2O72- + 14H+ → 6Fe3+ + 2Cr3+ + 7H2O(l) Find the mass of Fe. Find the percentage of Fe.

12.00 grams of acetic acid HC2H3O2 (Molar mass= 60.00 g/mol) are dissolved in 188.0 grams of water. Density of solution is 1.12g/mL.a. What is the wt/wt % concentration of the solution? b. What is the molarity of this solution? c. What is the molality of the solution?

A bottle of wine contains 12.5% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality.