Ch. 17 - Chemical ThermodynamicsSee all chapters
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

Entropy is the disorder or chaos associated with a system’s inability to convert thermal energy into mechanical work. 

Entropy and Spontaneity

Concept #1: The 2nd and 3rd Laws of Thermodynamics

The 2nd Law of Thermodynamics states systems (chemical reactions) spontaneously move to state of disorder. 

Concept #2: Entropy & Phase Changes

During a phase change as our molecules grow farther apart then entropy will increase. 

During a phase change as our molecules grow closer together then entropy will decrease.

Example #1: Which should have the highest molar entropy at 25oC?

Example #2: Which substance has greater molar entropy. 

Entropy and Phases

When comparing the entropy of different compounds then we must follow a set of guidelines in the following order. 

Example #3: Arrange the following substances in the order of increasing entropy at 25oC. 

Example #4: Containers A and B have two different gases that are allowed to enter Container C. Based on the image of Container C, what is the sign of entropy, ΔS°.

Practice: An ideal gas is allowed to expand at constant temperature. What are the signs of ∆H, ∆S & ∆G.

Whenever a phase change occurs, first determine if bonds are broken or formed to figure out the signs of enthalpy and entropy. Afterwards, determine if the reaction is spontaneous to determine the sign of Gibbs Free energy. 

Example #5: Consider the spontaneous fusion of ice at room temperature. For this process what are the signs for ΔH, ΔS and ΔG?

Practice: Consider the freezing of liquid water at 30°C. For this process what are the signs for ∆H, ∆S, and ∆G?

If bonds are broken then the entropy of a reaction increases, but if bonds are formed then the entropy of a reaction decreases. 

Practice: Predict the sign of ∆S in the system for each of the following processes:

a) Ag+ (aq) + Br - (aq) → AgBr (s)

b) CI2 (g) → 2 CI - (g)

c) CaCO3 (s) → CaO (s) + CO2 (g)

d) Pb (s) at 50°C → Pb (s) at 70°C

Practice: For each of the following reactions state the signs of ∆H (enthalpy) and ∆S (entropy):

a) Fusion of ice.

b) Sublimation of CO2

c) Vaporization of aqueous water.

d) Deposition of chlorine gas.

e) Condensation of water vapor. 


 Entropy and Calculations

The 2nd Law of Thermodynamics states that the entropy of the universe is always increasing and so it must always be greater than zero. 

Concept #3: The Universe & Entropy

The entropy of the universe takes the look at the entropy of our system (the chemical reaction) and of the universe. 

Concept #4: Total Entropy & Spontaneity

If the entropy is greater than zero then we classify the process as spontaneous. 

Concept #5: The Entropy of a Reaction

The entropy, enthalpy and Gibbs Free energy of a reaction is equal to products minus reactants. 

Example #6: The oxidation of iron metal is given by the following reaction: 

Practice: Diethyl ether (C4H10O2, MW = 90.1 g/mol) has a boiling point of 35.6oC and heat of vaporization of 26.7 kJ/mol. What is the change in entropy (in kJ/K) when 3.2 g of diethyl ether at 35.6oC vaporizes at its boiling point?

Concept #6: Trouton's Rule & Boltzmann's Equation 

Additional Problems
Which of the following has the smallest molar entropy at 298 K? 1. Ne(g) 2. F2(g) 3. N2(g) 4. Cl2(g) 5. He2(g)
When an aqueous solution containing Al 3+ at 25°C is mixed with an aqueous solution of hydroxide at 25°C an immediate precipitate of insoluble aluminum hydroxide is formed: Al 3+ (aq) + 3 OH – (aq) →  Al(OH)3 (s) The standard reaction enthalpy (ΔH°) of this reaction is -61.33 kJ/mol. a) Calculate ΔS°, ΔSsurr and ΔStot for this reaction
Which of the following processes result(s) in an increase in the entropy of the system? All systems are closed systems.  
For the dissociation reaction of the acid HF HF ⇌ H+ + F - ΔS is observed to be negative. The BEST explanation for this is: A. This is the expected result since each HF molecule produces two ions when it dissociates. B. Hydration of the ions produces the negative value of ΔS. C. The reaction is expected to be exothermic and thus ΔS should be negative. D. The reaction is expected to be endothermic and thus ΔS should be negative. E. None of these can explain the negative value of ΔS.
Consider the reaction of N2O5 at 25°C for which the following data are relevant: 2 N2O5 (g) ⇌ 4 NO2 (g) + O2 (g) What is ΔS° for the reaction (in J/K)? A. 89.5 B. 249.2 C. 453.8 D. 249.2 E. -115.6 
One of the major sources of NOx compounds in our atmosphere is the reaction between nitrogen and oxygen, for example N2(g) + 2O2(g) → 2NO2(g) This reaction is not favored at normal surface temperatures, but it does occur within internal combustion engines when air is mixed with the fuel to provide oxygen for the combustion reaction.    a. Before doing any calculations, predict the sign of ΔS°. ___________________.  Explain your reasoning.   b. Now calculate ΔH° and ΔS° for the above reaction. Some thermodynamic data is provided in the table below.   c. Is there a temperature range at which the above reaction would be spontaneous? If so, give the temperature range. If not, speculate on why the reaction occurs at higher temperatures.      
Which of the following species has the highest entropy (S°) at 25°C? A. MgCO3(s) B. CO(g) C. H2O(l)  D. CO2(g) E. CH3OH(l)
Which one of the following reactions is most likely to have a positive ΔS°? a) Cu2+ (aq) + 4 Cl -  (aq) → CuCl42-(aq) b) SiH4 (g) + 2O2 (g) → SiO2 (s) + 2 H2O (g) c) SiF4 (g) + 2 H2O (g)  → SiO2 (s) + 4 HF (g) d) H2O (l)  → H2O (s) e) NO (g) + O3 (g)  → NO2 (g) + O2 (g)    
Which one of the following reactions is likely to have a ΔS° close to zero (in other words, neither positive nor negative)? a) PCl 3(g) + Cl2(g) ⇌ PCl 3(g) b) 2KClO 3(s) ⇌ 2KCl(s) + 3O 2(g) c) CO(g) + H 2O(g) ⇌ CO 2(g) + H 2(g) d) CO 2(g) ⇌ CO 2(s) e) C 5H 12(l) + 8O 2(g) ⇌ 5CO 2(g) + 6H 2O(g)     Place the following compounds in order of increasing S°: PCl5(s)          PCl 5(g)          PCl 3(g) a) PCl5(s) < PCl5(g) < PCl3(g) b) PCl5(s) < PCl3(g) < PCl5(g) c) PCl5(g) < PCl5(s) < PCl3(g) d) PCl5(g) < PCl3(g) < PCl5(s) e) PCl3(g) < PCl5(g) < PCl5(s) f) PCl3(g) < PCl5(s) < PCl5(g)      
Ce2(SO4)3 becomes less soluble in water as temperature increases because it has a negative entropy of solvation. Most other salts become more soluble in water with increasing temperature because their entropy of solvation is positive. Which explanation best describes this discrepancy? a) The bond strength of Ce2(SO4)3 is very strong, which leads to an increase in the order of the system during the reaction. b) The highly charged Ce3+ and SO42- ions become surrounded by a uniquely ordered sphere of water molecules, which increases the order of the system. c) The solid structure of Ce2(SO4)3 lacks a highly ordered crystal structure thereby leading to a decrease in the order of the system during the reaction.  d) The ions Ce3+ and SO42- repel water molecules, which leads to a decrease in the order of the system during the reaction. e) There is no explanation for this phenomenon. 
For which of these processes is the value of Δ S expected to be negative? I. Sugar is dissolved in water. II. Steam is condensed. III. CaCO3 is decomposed into CaO and CO2. a) I only b) I and III only c) II only d) II and III only
In which process is entropy decreased ? a) dissolving sugar in water b) expanding a gas c) evaporating a liquid d) freezing water
HI has a normal boiling point of -35.4°C, and its ΔHvap is 21.16kJ/mol. Calculate the molar entropy of vaporization (ΔSvap). A. 68.6 J/K • mol B. 0.068 J/K • mol C. 598 J/K • mol D. 89.0 J/K • mol E. 75.2 J/K • mol
The diagram below shows the variation in entropy with temperature for a substance that is a gas at the highest temperature depicted. Accordingly, which of the following statements is not true? (a) The “zero point” is explained by the Second Law of Thermodynamics. (b) The entropy of a substance increases with temperature. (c) A solid has the least dispersed energy and the lowest entropy. (d) The vertical line 1 corresponds to ΔSfusion. (e) The increase in entropy for liquid  ⇌ gas is greater than for solid ⇌ liquid  
For which reaction, carried out at standard conditions, would both the enthalpy and entropy changes drive the reaction in the same direction? a) 2 H2 (g) + O2 (g) → 2 H2O (l)         ΔH = - 571.1 kJ b) 2 Na (s) + Cl2 (g) → 2 NaCl (s)      ΔH = - 822.0 kJ c) N2 (g) + 2 O2 (g) → 2 NO2 (g)        ΔH = + 67.7 kJ d) 2 NH3 (g) → N2 (g) + 3 H2 (g)        ΔH = + 92.4 kJ
Which of the following has the greatest entropy, S? (a) 1.00 mole of liquid water at 30° C (b) 1.00 mole of water vapor at 30° C (c) 1.00 mole of regular ice at -10° C  (d) 1.00 mole of “dry ice” (solid CO2) at -10° C (e) 1.00 mole of water under 10 atm of pressure at -10° C
Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 298 K.   N2(g) + 2 O2(g) → 2 NO2(g) ΔH = +66.4 kJ   a) ΔSsurr = +223 J/K b) ΔSsurr = -223 J/K c) ΔSsurr = -66.4 J/K d) ΔSsurr = +2656 kJ/K  
Which of these species has the highest entropy (S°) at 25°C? A) CH3OH(l) B) CO(g) C) MgCO3(s) D) H2O(l) E) Ni(s)
Which responses include all of the following processes that are acccompanied by an increase in entropy? 1. I2(s) → I2(g) 2. 2I(g) → I2(g) 3. 2NH3(g) → N2(g) + 3H2(g) 4. Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)   A) 1, 2 B) 1, 3 C) 3, 4 D) 3 E) 2, 4  
Which of the following processes would have a positive ΔSsys value? (a) He(g), 2 atm → He(g), 10 atm (b) 2 NO2(g) → N2O4(g) (c) H2(g) + I2(s) → 2 HI(g) (d) 2 Ag(s) + Br2(l) → 2 AgBr(s) (e) O2(g) → O2(aq)
Determine ΔS° for the reaction SO3(g) + H2O(l) → H2SO4(l).                  S° (J/K•mol) SO3(g)         256.2 H2O(l)         69.9 H2SO4(l)     156.9   A) 169.2   J/K•mol B) 1343.2 J/K•mol C) -169.2  J/K•mol D) -29.4    J/K•mol E) 29.4     J/K•mol
Elemental boron can be forrmed by reaction of boron trichloride with hydrogen.  BCl3(g) + 1.5H2(g) → B(s) + 3HCl(g) Substance:    BCl3(g)       H2(g)          B(s)         HCl(g) (J/K•mol):          ?            130.6         5.87      186.8   If ΔS°rxn = 80.3 J/K, what is S° for BCl3(g)? A) -18.2   J/K•mol B) 18.2    J/K•mol C) 290.1  J/K•mol D) 355.4  J/K•mol E) 450.6  J/K•mol
Identify the change in state for which there is an increase in the entropy of the system. A) water condensing B) crystallization of NaCl(s); NaCl(aq) → NaCl(s) C) compression of Air; air(1atm) → air(200 atm) D) ddry ice subliming E) water freezing
Which of the following processes is accompanied by a decrease in entropy of the system? A) C6H12O6(s) → 3CH3OH(l) + CO(g) + 2C(s) B) Ni(s) + 4CO(g) → Ni(CO)4(g) C) NaHCO3(aq) + HCl(aq) → H2O(l) + NaCl(aq) + CO2(g) D) NaClO3(s) → Na+(aq) + ClO31-(aq) E) None of the above
Calculate the normal boiling point of chloroform given that the standard entropy and enthalpy of vaporization of chloroform is +93.7 J/K/mol and 31.4 kJ/mol, respectively. 1. 215 K 2. 450 K 3. 405 K 4. 375 K 5. 335 K
Place the following in order of increasing molar entropy at 298 K. [Least (left) - Most (right)]     C(s)           O2(g)         Ne (g) A) C(s)    <   O2(g)    <   Ne (g) B) O2(g)  <   C(s)      <  Ne (g) C) Ne(g)   <  O2(g)      <  C(s) D) Ne(g)    <  C(s)        <  O2(g) E) C(s)       <  Ne(g)     <  O2(g)
Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 398 K. Predice whether or not this reaction will be spontaneous at this temperature. 2 N2(g) + O2(g) → 2 NO2(g)                   ΔH = +163.2 kJ A) ΔSsurr = -548 J/K, reaction is spontaneous B) ΔSsurr = -548 J/K, reaction is not spontaneous C) ΔSsurr = -410 J/K, reaction is not spontaneous D) ΔSsurr = -410 J/K, reaction is spontaneous E) ΔSsurr = -410 J/K, it is not possible to predict the spontaneity of this reaction without more information.
Calculate ΔS°rxn for the following rreaction. The S° for each species is shown below the reaction.                          H   2      +     Cl 2(g)   →   2HCl(g) S°(J/mol•K)     130.7         223.1         186.9 A) -20 J/K B) +20 J/K C) -166.9 J/K D) +166.9 J/K E) +466.2 J/K
Identify the change in state that  DOES NOT have an increase in entropy of the system. A) water evaporating B) water boiling C) ice melting D) dry ice subliming E) water freezing
In which example does entropy increase? I. A piece of fruit freezes in liquid nitrogen. II. Librarians put library books back onto shelves at the end of the day. III. Liquid nitrogen boils in a beaker at room temperature. IV. Dry ice sublimes. V. A balloon collapses as its contents cool in liquid nitrogen. 1. I, III, IV, or V only 2. IV or V only 3. I, II, III, IV, or V 4. II only 5. IV only 6. II or III only 7. III only 8. II or IV only 9. III or IV only
Which of the following processes shows a decrease in entropy of the system? A) CH3OH(l) → CO(g) + 2H2(g) B) COCl2(g) → CO(g) + Cl2(g) C) 2 NO(g) + O2(g) → 2 NO2(g) D) NaClO3(s) → Na+(aq) + ClO3-(aq) E) None of the above will show a decrease in entropy.  
Predict which substance in each pair has the greater molar entropy: a) butane, CH3CH2CH2CH3 or 2-butene, CH 3CH=CHCH3 b) Ne (g) or Xe (g) c) CH4 (g) or CCl4 (l) d) CH3OH (l) or C 2H5OH (l) e) KClO3 (s) or KClO3 (aq) f) Na (s) or K (s)
Which of the following would probably have a positive ∆S value? 1. O2(g) → O2(aq) 2. He(g, 2 atm) → He(g, 10 atm) 3. 2 NO2(g) → N2O4(g) 4. 2 Ag(s) + Br2(l) → 2 AgBr(s) 5. H2(g) + I2(s) → 2 HI(g)
Predict the sign of ΔS for each of the following: a) A piece of wax melting b) Silver chloride precipitating from solution c) Alcohol evaporating d) A solid explosive converting to a gas e) 2 K(s) + F2 g) → 2 KF(s) f) NH3(g) + HBr(g) → NH4Br(s) g) NaClO3(s) → Na+(aq) + ClO3- (aq)
Place the following in order of increasing molar entropy at 298 K. CO2          C 3H 8             SO A) CO2 < C3H8 < SO B) C3H8 < CO2 < SO C) CO2 < SO < C3H8 D) SO < C3H8 < CO2 E) SO < CO2 < C3H8
Consider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 398 K. Predict whether or not this reaction will be spontaneous at this temperature. 4 NH3(g) + 3 O2(g)  →  2 N2(g) + 6 H2O(g) ΔH = -1267 kJ A) ΔSsurr = +3.18 kJ/K, reaction is spontaneous B) ΔSsurr = -12.67 kJ/K, reaction is spontaneous C) ΔSsurr = +50.4 kJ/K, reaction is not spontaneous D) ΔSsurr = +12.67 kJ/K, reaction is not spontaneous E) ΔSsurr = -3.18 kJ/K, it is not possible to predict the spontaneity of this reaction without more information.  
Calculate the standard entropy of fusion of ethanol at its melting point 159 K. The standard molar enthalpy of fusion of ethanol at its melting point is 5.02 kJ · mol−1. 1. −44.0 J · K−1· mol−1 2. −5.02 kJ · K−1· mol−1 3. −31.6 J · K−1· mol−1 4. +5.02 kJ · K−1· mol−1 5. +31.6 J · K−1· mol−1
Calculate the change in the standard entropy of the system, ΔS°, for the synthesis of ammonia from N2(g) and H2(g) at 298 K.  S° (N2) = 191.5 J/mol•K S° (H2) = 130.6 J/mol•K S° (NH3) = 192.5 J/mol•K
Consider the reaction of N2O5 at 25°C for which the following data are relevant: 2 N2O5 (g) → 4 NO2 (g) + O2 (g) Substance             ΔH°f                               S°              N 2O5                    11.29 kJ/mol             355.3 J/K mol               NO 2                     33.15 kJ/mol             239.9 J/K mol               O 2                                   ?                     204.8 J/K mol   What is ΔS° for the reaction (in J/K)? a) 89.5 b) 249.2 c) 453.8 d) 249.2 e) -115.6
Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction. C2H2(g) + H2(g) → C2H4(g) S°(J/mol·K)              200.9             130.7               219.3 A) +112.3 J/K B) +550.9 J/K C) -550.9 J/K D) +337.1 J/K E) -112.3 J/K    
A system releases 900 J of heat to the surroundings, which are at a constant 27 ◦C. What is ∆S of the surroundings? 1. 33.3 J · K−1 2. −3 J · K−1 3. 3 J · K−1 4. −33.3 J · K−1
HI has a boiling point of –35.4 oC with a standard enthalpy of vaporization of 21.16 kJ/mol. Calculate the standard entropy of vaporization of HI. a) 598 J/K·mol b) 68.6 J/K·mol c) 75.2 J/K·mol d) 0.068 J/K·mol e) 89.0 J/K·mol
Which of the following reaction(s) is/are predicted to have favorable ∆S ̊rxn? a) N2 (g) + 3 H2 (g) → 2 NH3 (g) b) H2O (l) → H2O (s) c) C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) d) Both a and b e) None of the above
Benzene has a ΔHvap = 33.90 kJ/mol and a ΔSvap = 96.4 J/mol-K. What is the vaporization temperature of Benzene in Celsius? A. −273 B. 78.5 C. 352 D. 2570 E. 2840
The compound benzoic acid, C6H5COOH, melts at 122.4 ̊C. If the enthalpy of fusion of this compound is 17.3 kJ/mol, what is its entropy of fusion? a. 31.3 J/mol·K b. 34.1 J/mol·K c. 38.0 J/mol·K d. 40.2 J/mol·K e. 43.8 J/mol·K
Consider the following figure of four processes from the initial state. The substances are in gas phase initially. Which process(es) would result in an entropy increase?   A. (1) and (2)  B. (1) and (3) C. only (3) D. (1), (2), and (4) E. only (4)  
Balance the following reaction and then solve for the ∆S (J/K-mol) for this reaction. Li (g) + H2(g) → LiH (s) With S° (J/K-mol) value of LiH = 20.0          Li = 138.7        H   2 = 130.6 A. −368.0 B. −249.3 C. −106.8 D. 249.3 E. 368.0  
  Explain the following plot:
Of the following descriptions, how many (the total number) would increase entropy? Sublimation of sodium; C2H6 (g) → C2H2 (g) + 2 H2(g); Heating hexane; Boiling water A.none of them B. 1 C. 2 D. 3 E. All of them
Consider the following processes (Treat all gases as ideal). 1. Nitrogen gas is compressed isothermally to one half its original volume. 2. Carbon dioxide is allowed to expand isothermally to 10 times its original volume. 3. A glass of water loses 100 J of energy reversibly at 30°C. 4. The temperature of one mole of helium is increased 25°C at constant pressure. 5. The pressure of one mole of oxygen gas is allowed to double isothermally.   Which of these processes leads to an increase in entropy?   a) 1 and 4         b) 5         c) 3 and 5         d) 2 and 4         e) 1 and 2  
For which process is the entropy change per mole the largest at constant temperature?  (A) H2O(l) → H2O(g) (B) H2O(s) → H2O(g) (C) H2O(s) → H2O(l) (D) H2O(l) → H2O(s)
Which of the following processes have a positive entropy term?   A. Synthesis of ammonia from nitrogen and hydrogen gas. B. Creation of sodium bicarbonate from gaseous water, carbon dioxide and sodium carbonate C. Freezing of methanol D. Creation of carbon monoxide and hydrogen gas from gaseous methane and gaseous water E. All of the above have a positive entropy term. 
Which of the following would have the   highest value of absolute entropy per mole? a) Water at 50 oC b) Water at 10 oC c) Ice at -10 oC d) 1 M NaCl at 50 oC e) 1 M NaCl at 10 oC  
Which of the following phase changes is correctly paired with the sign of its change in entropy and its change in enthalpy?
What are the signs for the change in enthalpy and change in entropy when a system undergoes the phase transition of freezing? A. ∆H < 0 , ∆S < 0 B. ∆H > 0 , ∆S > 0 C. ∆H < 0 , ∆S > 0 D. ∆H > 0 , ∆S < 0
Which of the following statements describes situations where entropy increases: I. Increase in number of gas particles present II. Separated gas particles in a flask being allowed to mix III. Gas particles undergo deposition   A. Only I                 B. Only II                 C. Only III               D. I and II               E. All three
Rank the following compounds in order of increasing entropy at 25°C? A. MgCO3 (s) B. CO (g) C. Ni (s) D. H2O (I) E. CH3OH (I)
Would you expect the entropy of the system to  increase or decrease for each of the following processes: a. CaCO3 (s) → CaO (s) + CO2 (g)       ________________   b. H2O (g) → H2O (l)                             ________________
When temperature is increased and pressure is held fixed across a phase change which of the following statements is true? A. Entropy is negative and enthalpy is positive. B. Entropy is negative and enthalpy is negative. C. Entropy is positive and enthalpy is positive. D. Entropy is positive and enthalpy is negative.
Coal is a major source of energy that can be converted from its solid, raw form to a gaseous phase of fuel. This is accomplished by the water gas reaction: C (s) + H2O (g)      →      CO (g) + H2 (g) What is the entropy value for the water gas reaction shown above?   A. – 268 kJ/mol B. – 134 kJ/mol C. 0 kJ/mol D. +134 kJ/mol
Which of the following reactions would be entropically favored?   A) Precipitation of ions from a supersaturated solution. B) Deposition of gaseous carbon dioxide. C) Ionization of an organic compound. D) The fusion of inorganic nuclides. 
Arrange the following substances in the order of increasing entropy at 25° C.               CO 2 (s)         Kr (g)         S  8 (s)         O 3 (g)         H 2O (l)         H 2S (l)
Which of the following statements describes situations where entropy increases: I.  Increase in number of gas particles present II.  Separated gas particles in a flask being allowed to mix III.  Gas particles undergo deposition   A.  Only I                  B.  Only II                  C.  Only III                   D.  I and II                  E.  All three
Consider the following processes (at 298 K) given below and determine for which is ΔS positive?
Consider the following reaction at constant pressure. Use the information here to determine the value of ∆Ssurr at room temperature. Predict whether or not this reaction will be spontaneous at this temperature. N2 (g) + 2 O2 (g) → 2 NO2 (g)              ∆H° = + 66.4 kJ ∆Ssurr = - 223J/K, not spontaneous ∆Ssurr = + 265 J/K, not spontaneous ∆Ssurr = + 223 J/K, is spontaneous ∆Ssurr = - 66.4 J/K, not spontaneous ∆Ssurr = - 66.4 J/K, not possible to predict the spontaneity 
Predict the sign on ΔS° for the following reactions i. 2 KClO4 (s) → 2 KClO3(s) + O2(g) ii. Propanol condenses at room temperature iii. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)            Reaction i          Reaction ii          Reaction iii A.          +                            +                           - B.           -                             +                          + C.           +                             -                          0  D.            -                            +                          0 E.            +                            -                          -   
Rank the standard molar entropy of the following from lowest to highest. 1. H2O2 (l) 2. H2O (g) 3. H2O (l) 4. H2O2 (aq) a) 4 < 1 < 3 < 2     b) 1 < 3 < 4 < 2 c) 3 < 1 < 4 < 2 d) 2 < 4 < 3 < 1 e) 1 < 3 < 2 < 4 
Would you expect the entropy of the system to  increase or decrease for each of the following processes: a. N2 (g) + 3H2 (g) → 2NH3 (g)       ________________   b. H2O (l) → H2O (g)                        ________________
True or false: An endothermic process increases the entropy of the surroundings. ________
Predict how the entropy of the substance is affected in the following processes. CH4(g, 125°c) → CH4(g, 200°C)  a) increases b) decreases c) remains the same
For the following questions circle the correct answer. There is one and only one correct answer. The substance with the largest value for entropy (at T = 25.0 °C and p = 1.00 atm). a) CH3CH2CN(l) b) CH3CN(I) c) CH3CH2CN(g) d) CH3CN(g)
Why does the solubility of NaCl only increase slowly with water temperature?A. ΔSsol > 0 but small in magnitudeB. ΔSsol < 0 but small in magnitudeC. ΔHsol > 0 but small in magnitudeD. ΔHsol < 0 but small in magnitudeE. it has a very large lattice energy
Consider the following reaction at 298 K 2Al (s) + 3Cl2 (g) → 2AlCl3 (s)         H=-1408 KJ Calculate the following quantities: (a) Ssys= ?  (b) Ssurr= ? (c) Suniv= ?
Using the following data, calculate ΔSfus and ΔSvap for HBr.Determine the entropy change when 4.80 mol of HBr (f) freezes at atmospheric pressure. 
CO(NH2)2(aq) + H2O(l) → CO2(g) +2NH3(g) ΔS° = +354.8 J/mol*KGiven the data below, calculate the ΔS° f for UreaSubstance S° (J/molK)H2O (l) 69.96CO2 (g) 213.6NH3 (g) 192.5 
Which of the following reactions have a positive ΔS rxn?  a) 2 A(g) + B(s) → 3 C(g) b) 2 A(g) + B(g) → C(g) c) A(g) + B(g) → C(g) d) 2 A(g) + 2 B(g) → 5 C(g) e) More than one of the above
Which of the following reactions have a positive ΔSrxn? Check all that apply. A. A(g) + B(g) → 3 C(g) B. A(g) + B(s) → C(g) C. A(g) + B(g) → C(g) D. A(g) + 2 B(g) → C(g)
ΔS is positive for the reaction _________________.a. 2NO(g) + O 2(g) → 2NO2(g)b. 2N2(g) + 2H2(g) → 2NH3(g)c. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) d. Mg(s) + Cl2(g) → MgCl2(s)e. C2H4(g) + H2(g) → C2H6(g)
The enthalpy of vaporization of acetone is 31.3 kJ/mol, and its boiling point is 56.3°C. What is the entropy change for the vaporization (boiling) of acetone?
A favorable entropy change occurs when ΔS is positive. What can be said about the order of the system when ΔS is positive. a) system order increases b) system order stays the same c) system disorder increases
Calculate the standard entropy change for the following reaction at 25°C.MgCl2(s) + H2O(l) → MgO(s )+ 2HCl(g)
Predict the sign of the entropy change, ΔS°, for each of the reaction displayed. Drag the appropriate items to their respective bins.
Consider the following reaction at 298 K: 2C (graphite) + O2 (g) → 2CO (g)  Delta H = -110.5 kJ Calculate: Delta S(sys) J/K Delta S (surr) J/K Delta S (Univ) J/K
The ΔH°vap for pure water is 40.65 kJ/mol. Calculate the ΔS°vap for pure water.
Predict the sign of the entropy change, ΔS°, for the following reaction. Pb2+ (aq) + 2Cl− (aq) → PbCl2(s) a) Negative b) Positive                                                   
The enthalpy of vaporization of methanol is 35.27 kJ mol-1 at its boiling point of 64.1°Ca. Calculate the entropy of vaporization of methanol at this temperature.b. Calculate the entropy of surroundings.
Which of the following statements describes situations where entropy increases:                                     I.  Increase in number of gas particles present                                     II.  Separated gas particles in a flask being allowed to mix                                     III.  Gas particles undergo deposition   A.  Only I              B.  Only II        C.  Only III        D.  I and II       E.  All three
Predict the sign of the entropy change, ΔS°, for each of the reaction displayed. i) 2NO2 (g) → N2 (g) + 2O2 (g) ii) C5H12 (g) + 8O2 (g) → 5CO2 (g) + 6H2O (g) iii) 2NaClO3 (s) → 2NaCl (s) + 3O2 (g) iv) 2Na (s) + Cl2 (g) → 2NaCl (s) v) CH3OH (l) → CH3OH (g)
HI has a boiling point of –35.4°C with a standard enthalpy of vaporization of 21.16 kJ/mol. Calculate the standard entropy of vaporization of HI.a) 598 J/K·molb) 68.6 J/K·molc) 75.2 J/K·mold) 0.068 J/K·mole) 89.0 J/K·mol
Which of the following reactions have a positive delta S rxn? Check all that apply.
How many of the following processes represent an increase in entropy:* Water is heated in the microwave from 23 Celsius to 90 Celsius* The sublimation of I2* CO 2 gas is dissolved in water to make a carbonated beverage* N2O4 (g) → 2 NO2 (g)A. noneB. oneC. twoD. threeE. all four
The thermodynamic quantity that expresses the degree of disorder in a system is _________. a. enthalpy b. internal energy c. bond energy d. entropy e. heat flow
Which one of the following processes produces a decrease in the entropy of the system? a. boiling water to form steam b. dissolution of solid KCl in water c. mixing of two gases into one container d. freezing water to form ice e. melting ice to form water 
ΔS is positive for the reaction _______. a. CaO(s) + CO2(g) → CaCO3(s) b. N2(g) + 3H2(g) → 2NH3(g) c. 2SO3(g) → 2SO2(g) + O2(g) d. Ag+(aq) + Cl-(aq)→AgCl(s) e. H2O(l) → H2O(s)   
For one mole of substance at a given temperature, select the member in each pair with the higher entropy.a. P2(g), P4(g)b. CaF2(s), BaCl2(s)c. CuSO4(s), CuSO4•5H2O(s)
Which of the following reaction(s) is/are predicted to have favorable ∆S°rxn? a) N2 (g) + 3 H2 (g) → 2 NH3 (g) b) H2O (l) → H2O (s) c) C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) d) Both a and b e) None of the above
For a given compound, list the decreasing order of entropy for a solid, liquid, and gas.a. solid > gas > liquidb. liquid > solid > gasc. gas > liquid > solidd. gas > solid > liquide. solid > liquid > gas
Calculate the standard entropy change for the following reaction at 25°C. 2CH3OH(g) + 3O2(g) → 2CO2(g) + 4H2O(g)
Nitric oxides, NO and NO2, contribute to air pollution, acid rain, and the depletion of the ozone layer. After NO forms in the combustion chamber of an automobile engine, it reacts further with oxygen to form NO2. The reaction is given by 2NO(g) + O2(g) → 2NO2(g) Calculate ΔSrxn∘ for the reaction.
Predict how the entropy of the substance is affected in the following processes:
Which of the following processes involves a decrease in entropy? a. the decomposition of NH 3 (g) b. the condensation of steam c. the sublimation of CO2  d. the evaporation of ethanol e. the dissolution of NH4NO3(s) in water f.  I2 at 90oC and 5.0 atm  →  I2 at 50oC and 10.0 atm g. NH4Cl(s) → HCl(g) +  NH3(g) h. CH4(g)  +  2 O2(g)  →  CO2(g)  +  2 H2O(l) 
Which reaction is/are predicted to have a negative entropy of reaction? a) CH3CH2OH (s) → CH3CH2OH (l) b) CH3CH2OH (l, 10 ̊C) → CH3CH2OH (l, 50 ̊C) c) CH3CH2OH (l, 50 ̊C) → CH3CH2OH (l, 10 ̊C) d) Both a and b e) Both a and c
Predict how the entropy of the substance is affected in the following process:                                            Ar(l) → Ar(g)  a) increases b) decreases  
Calculate ΔS∘rxn for this balanced chemical equation. 2NO(g) + O2(g) → 2NO2(g) Express your answer to one decimal place and include the appropriate units.
Given the standard entropy values in the table below, determine the standard entropy change of the reaction below that produces 10.0 g of metallic Cu. 
Predict how the entropy of the substance is affected in the following process? Br2 (l, 1 bar, 25°celcius) yields Br2 (g, 1 bar, 25°Celsius) a) Increases b) decreases c) stays the same
Using the data in the table, calculate the standard entropy changes for the following reactions at 25°.
Given the values of ΔH∘rxn, ΔS∘rxn, and T below, determine ΔSuniv. a. ΔH∘rxn = 84 kJ , ΔS∘rxn = 144 J/K , T = 303 K b. ΔH∘rxn = 84 kJ , ΔS∘rxn = 144 J/K , T = 762 K c. ΔH∘rxn = 84 kJ , ΔS∘rxn = −144 J/K , T = 303 K d. ΔH∘rxn = − 84 kJ , ΔS∘rxn = 144 J/K , T = 406 K
Which of the following processes have a ΔS > 0? a. 2NH3(g) + CO2(g) → NH2CONH2(aq) + H2O(l) b. lithium fluoride forms from its elements c. 2HF(g) → H2(g) + F2(l) d. potassium iodide dissolves in pure water
Which of the following is true for an endothermic process?a. qsys > 0, ΔSsurr < 0b. qsys < 0, ΔSsurr > 0c. qsys < 0, ΔSsurr < 0d. qsys > 0, ΔSsurr > 0
Which process will decrease entropy? a. SO2(l) → SO2(g) b. H2O(g) → H2O(l) c. CaCO3(s) → CaO(s) + CO2(g) d. 2Cl2O(g) → 2Cl2(g) + O2(g)
Given the values of ΔH∘rxn, ΔS∘rxn, and T below, determine ΔSuniv. a) ΔH∘rxn = 87 kJ , ΔS∘rxn = 146 J/K , T= 296 K, will this be spontaneous or not spontaneous? b) ΔH∘rxn = 87 kJ , ΔS∘rxn = 146 J/K , T= 762 K, will this be spontaeous or not spontaneous? c) ΔH∘rxn = 87 kJ , ΔS∘rxn = −46 J/K , T= 296 K, will this be spontaneous or not spontaneous? d) ΔH∘rxn = −87 kJ , ΔS∘rxn = 146 J/K , T= 390 K, will this be spontaneous or not spontaneous?
Entropy is a measure of a. free energy b. the heat of a reaction c. molecular randomness d. the rate of a reaction
Arrange these gases in order of decreasing standard molar entropy: Rank from largest to smallest. Cl2 SO3 Kr
Rank these systems in order of decreasing entropy. Rank from highest to lowest entropy. To rank items as equivalent, overlap them. A) 1 mol carbon tetrafluoride gas at 273k 40L B) 1 mol krypton gas at 273K 40L C) 1/2 mol krypton gas at 100k 20L D) 1 mol krypton gas at 273K 20L E) 1/2 mol krypton liquid at 100K F) 1 mol fluorine gas 273 K 40L G) 1/2 mol krypton gas at 273K 20L
Calculate ΔSfus and ΔSvap for Na.
The heat of vaporization of methanol, CH3OH, is 35.2 kJ/mol. Its boiling point is 64.6°C. What is the change in entropy for the vaporization of methanol?
Calculate the boiling point of benzene, C6H6 from the data given below:C6H6 (l) → C6H6 (g)  
Given the values of ΔHºrxn, ΔSºrxn, and T below determine ΔSuniv.ΔHºrxn = -81 kJ,ΔSrxn = -149 J/K,T = 301 ºKExpress your answer using two significant figures.
Consider the following reaction at 298 K: C(graphite) + 2Cl2(g) -->CCl4(l) Δ H = -139 kJ Calculate the following quantities. Find standard entropy values here.
The normal boiling point of ethanol (C2H5OH) is 78.3 ° C and its molar enthalpy of vaporization it 38.56 kJ/mol. What is the change in entropy of the system in J/K when 77.2 grams of ethanol at 1 atm condenses to a liquid at the normal boiling point?825-825-263-184263
A 15 g piece of metal (138.4 g/mol) melts at 1774 °C and its enthalpy of fusion is 17.4/mol. Calculate the entropy of fusion (J/K) of the metal. Enter to 2 decimal places.
Consider the reaction: I2 (g) + Cl2 (g) → 2ICl (g) Using standard absolute entropies at 298K, calculate the entropy change for the system when 2.49 moles of I2 (g) standard conditions. 
The temperature of a 874 g piece of granite is increased from 19.2°C to 69.2°C. What is its change in entropy J/K)? The specific heat capacity of granite is 0.790 J/g • K.
The ΔHvapo of a certain compound is 13.08 kJ mol-1 and its ΔSvapo is 67.74 J mol-1 K-1.What is the normal boiling point of this compound?
Using the data in the table, calculate the standard entropy changes for the following reactions at 25 degree C.S(s) + O2(g) --> SO2(g)MgCO3(s) --> MgO(s) + CO2(g)2C2H6(g) + 7O2(g) --> 4 CO2(g) + 6H2O(l)
Calculate the standard entropy change for the following reaction at 25 °C. S° values can be found here.C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (g)
Nitric oxides, NO and NO2, contribute to air pollution, acid rain, and the depletion of the ozone layer. After NO forms in the combustion chamber of an automobile engine, it reacts further with oxygen to form NO2. The reaction is given by2NO (g) + O2 (g) → 2NO2 (g) The following table gives some entropy values: Part ACalculate ΔS°rxn for the reaction 2NO (g) + O2 (g) → 2NO2 (g) Express your answer to one decimal place and include the appropriate units. Part BA negative change in entropy indicates that (i) the products are more disordered than the reactants (ii) the products are less disordered than the reactants
Consider the reaction:3 Fe2O3 (s) + H2 (g) --> 2Fe3O4 (s) + H2O(g)Using standard absolute entropies at 298K, calculate the entropy change for the system when 2.29 moles of Fe2O3(s) react at standard conditions ΔSº system = _____ J/K
Entropy of Reaction for Nitrogen Dioxide Formation Nitric oxides. NO and NO2, contribute to air pollution, acid rain, and the depletion of the ozone layer. After NO forms in the combustion chamber of an automobile engine, it reacts further with oxygen to form NO2. The reaction is given by 2NO (g) + O2 (g) → 2NO2 (g) The following table gives some entropy values: Part ACalculate ΔS°rxn for the reaction 2NO (g) + O2 (g) → 2NO2 (g)
Calculate the standard entropy change for the following reaction, 2SO2 (g) + O2 (g) → 2SO3 (g) given S° [SO2 (g)] = 248.2 J/K • mol. S° [O2 (g)] = 205. 1 J/K • mol, and S° [SO3 (g)] = 256.8 J/K • mol. (a) -196.5 J/K • mol-rxn (b) -94.0 J/K • mol-rxn (c) -187.9 J/K • mol-rxn (d) +187.9 J/K • mol-rxn (e) +196.5 J/K • mol-rxn
Using the following data, calculate ΔSfus and  ΔSvap for Na.
The ΔHvap of a certain compound is 28.26 kJ mol and its ΔSvap is 50.01 J•mol-1•K-1. What is the boiling point of this compound?
Suppose a heat source generates heat at a rate of 54.0 W (1 W = 1 J/s). How much entropy does this produce per hour in the surroundings at 25.0 °C? Assume the heat transfer is reversible.
Given the hypothetical reaction. 4 X(s) + 6Y(s) → 4Z (s) + 9A(g) Calculate Δ S for this reaction at 25°C, given the following absolute entropies: S°J/(K-mol) X (s) 40.72 Y(s) 28.64 Z(s) 66.92 A(g) 54.98
Part BCalculate the standard entropy change for the reaction P4 (g) + 5O2 (g) → P4O10 (s) using the data from the following table: Express your answer in joules per kelvin using four significant figures.
Use the data from this table of thermodynamic properties to calculate the values of delta S°rxn for each of the following reactions at 25 °C. (a) 4NH3 (g) + 7O2 (g) → 4NO2 (g) + 6H2O (g)      (b) N2 (g) + O2 (g) → 2NO (g) 
Calculate ΔS° compositefunction (in J/mol • K) for the following reaction. 2HCl (g) + Pb (s) → PbCl2 (s) + H2 (g)
Using the following data, calculate ΔSfus and ΔSvap for Cs. 
The ΔHvap of a certain compound is 48.17 kJ mol-1 and its ΔSvap is 52.91 J mol-1•K-1. What is the boiling point of this compound?
Which of the following processes shows a decrease in entropy of the system? NaClO3 (s) → Na+ (aq) ClO3- (aq) CH3OH (l) → CO (g) + 2H 2 (g) H2O(l) → H2O (g) 2NO (g) + O2 (g) → 2NO2 (g) COCl2 (g) → CO (g) + Cl 2 (g) 
Use the data from this table of thermodynamic properties to calculate the values of ΔS°rxn for each of the following reactions at 25° C. 
A reaction had ΔH°rxn = - 130 kJ and ΔS°rxn = 316 J/K. Part AAt what temperature is the change in entropy for the reaction equal to the change in entropy for the surroundings? Express your answer in kelvins. 
Calculate the standard entropy change for the following reaction at 25 °C. S° values can be found here. HCl (g) + NaOH (s) → NaCl (s) + H2O (l) 
Calculate the standard entropy change for the following reaction at 25°C. S° values can be found here.HCl(g)+ NaOH(s) → NaCl(s) + H2O(l)
Calculate the standard entropy change for the following reaction at 25°C. S° values can be found here. Mg(OH)2 (s) + 2HCl (g) → MgCl2 (s) + 2H2O (g) 
Identify the process in which the entropy increases.a. the phase transition from a solid to a gasb. the phase transition from a gas to a solidc. the phase transition from a gas to a liquidd. the phase transition from a liquid to a solide. a decrease in the number of moles of a gas during a chemical reaction 
The entropy of 0.002 mole of CH2CI2 (aq) is greater than the entropy of 0.002 mole of CH2CI2 (l).a. Trueb. False
Entropy is a measure of a. free energy. b. the heat of a reaction. c. the rate of a reaction. d. molecular randomness. 
The entropy of 0.5 mole LiBr (s) at 290 K is greater than the entropy of 0.5 mole LiBr (s) at 330Ka. Trueb. False 
Place the following in order of increasing standard molar entropy.H2O(l) H2O(g) H2O(s) a. H2O(g), H2O(s), H2O(l) b. H2O(l), H2O(s), H2O(g) c. H2O(g), H2O(l), H2O(s) d. H2O(s), H2O(l), H2O(g) 
Which provides the greatest decrease in entropy?
Sodium reacts violently with water according to the equation: 2 Na(s) + 2 H2O(l) →2NaOH(aq) + H2(g) The resulting solution has a higher temperature than the water prior to the addition of sodium. What are the signs of ΔH°and ΔS° for this reaction?a. ΔH° is negative and ΔS° is positive.b. ΔH° is positive and ΔS° is negative. c. ΔH° is negative and ΔS° is negative. d, ΔH° is positive and ΔS° is positive. 
The entropy of 1 mole of N2 (g) is greater than the entropy of 1 mole of N2(aq).a. Trueb. False 
Calculate ΔS°rxn for the following reaction:4Cr(s) + 3O2(g) → 2Cr2O3(s).Substance            ΔS°, J/K·molCr(s)                        23.77O2(g)                       205.138Cr2O3(s)                  81.2a. 548.1 J/Kb. 147.7 J/Kc. -147.7 J/Kd. -548.1 J/K
Select the molecule with the highest gas-phase absolute entropy at 25 ºC. a) CH4 b) C4H10 c) C3H8 d) C2H6
Which of the following would have the highest entropy assuming one mole of each substance and the same temperature for each. a) HBr(g) b) H2(g) c) HBrO4 d) He(g)
Without referring to a data table, rank the following compounds by standard molar entropy.i) CH3OH (g)ii) O2 (g)iii) N2 (g) 
What is the ΔSo if the  ΔHo is +88.00 kJ and ΔGo  is +11.21 kJ? a) +0.258 J b) -258 J c) +258 J
Consider the following reaction at 298 K:2 H2 (g) + O2 (g) → 2 H2O (g)     ΔH= -483.6 KJCalculate the following quantities.i) ΔSsys=ii) ΔSsurr=iii) ΔSuniv=
Rank these systems in order of decreasing entropy.Rank from highest to lowest entropy. To rank items as equivalent, overlap them.i) 1 mol of oxygen gas at 273 K and 40 Lii) 1/2 mol of xenon gas at 100 K and 20 Liii) 1 mol of xenon gas at 273 K and 20 Liv) 1/2 mol of liquid xenon at 100 Kv) 1 mol of xenon gas at 273 K and 40 Lvi) 1 mol of carbon tetrachloride gas at 273 K and 40 Lvii) 1/2 mol of xenon gas at 273 K and 20 L