🎉 Announcing Numerade's $26M Series A, led by IDG Capital!Read how Numerade will revolutionize STEM Learning

Chapter 18

Free Energy and Thermodynamics

Educators

KC
+ 1 more educators

Problem 1

What is the first law of thermodynamics, and how does it relate to energy use?

Linhan Y.
Numerade Educator

Problem 2

What is nature's heat tax, and how does it relate to energy use?

KC
Kevin C.
Numerade Educator

Problem 3

What is a perpetual motion machine? Can such a machine exist given the laws of thermodynamics?

Linhan Y.
Numerade Educator

Problem 4

Is it more efficient to heat your home with a natural gas furnace or an electric furnace? Explain.

KC
Kevin C.
Numerade Educator

Problem 5

What is a spontaneous process? Provide an example.

Linhan Y.
Numerade Educator

Problem 6

Explain the difference between the spontaneity of a reaction (which depends on thermodynamics) and the speed at which the reaction occurs (which depends on kinetics). Can a catalyst make a nonspontaneous reaction spontaneous?

KC
Kevin C.
Numerade Educator

Problem 7

What is the precise definition of entropy? What is the significance of entropy being a state function?

Linhan Y.
Numerade Educator

Problem 8

Why does the entropy of a gas increase when it expands into a vacuum?

KC
Kevin C.
Numerade Educator

Problem 9

Explain the difference between macrostates and microstates.

Linhan Y.
Numerade Educator

Problem 10

Based on its fundamental definition, explain why entropy is a measure of energy dispersion.

KC
Kevin C.
Numerade Educator

Problem 11

State the second law of thermodynamics. How does the second law explain why heat travels from a substance at higher temperature to one at lower temperature?

Linhan Y.
Numerade Educator

Problem 12

What happens to the entropy of a sample of matter when it changes state from a solid to a liquid? From a liquid to a gas?

KC
Kevin C.
Numerade Educator

Problem 13

Explain why water spontaneously freezes to form ice below 0 C even though the entropy of the water decreases during the state transition. Why is the freezing of water not spontaneous above 0 C?

Linhan Y.
Numerade Educator

Problem 14

Why do exothermic processes tend to be spontaneous at low temperatures? Why does their tendency toward spontaneity decrease with increasing temperature?

KC
Kevin C.
Numerade Educator

Problem 15

What is the significance of the change in Gibbs free energy (G) for a reaction?

Linhan Y.
Numerade Educator

Problem 16

Predict the spontaneity of a reaction (and the temperature dependence of the spontaneity) for each possible combination of signs for H and S (for the system).

a. H negative, S positive
b. H positive, S negative
c. H negative, S negative
d. H positive, S positive

KC
Kevin C.
Numerade Educator

Problem 17

State the third law of thermodynamics and explain its significance.

Linhan Y.
Numerade Educator

Problem 18

Why is the standard entropy of a substance in the gas state greater than its standard entropy in the liquid state?

KC
Kevin C.
Numerade Educator

Problem 19

How does the standard entropy of a substance depend on its molar mass? On its molecular complexity?

Linhan Y.
Numerade Educator

Problem 20

How can you calculate the standard entropy change for a reaction from tables of standard entropies?

KC
Kevin C.
Numerade Educator

Problem 21

Describe the three different methods to calculate G for a reaction. Which method would you choose to calculate G for a reaction at a temperature other than 25 C?

Linhan Y.
Numerade Educator

Problem 22

Why is free energy 'free'?

KC
Kevin C.
Numerade Educator

Problem 23

Explain the difference between G and G.

Linhan Y.
Numerade Educator

Problem 24

Why does water spilled on the floor evaporate even though G for the evaporation process is positive at room temperature?

KC
Kevin C.
Numerade Educator

Problem 25

How do you calculate the change in free energy for a reaction under nonstandard conditions?

Linhan Y.
Numerade Educator

Problem 26

How does the value of G for a reaction relate to the equilibrium constant for the reaction? What does a negative G for a reaction imply about K for the reaction? A positive G?

KC
Kevin C.
Numerade Educator

Problem 27

Which of these processes is spontaneous?

a. the combustion of natural gas

b. the extraction of iron metal from iron ore

c. a hot drink cooling to room temperature

d. drawing heat energy from the ocean's surface to power a ship

Linhan Y.
Numerade Educator

Problem 28

Which of these processes are nonspontaneous? Are the nonspontaneous processes impossible?

a. a bike going up a hill

b. a meteor falling to Earth

c. obtaining hydrogen gas from liquid water

d. a ball rolling down a hill

KC
Kevin C.
Numerade Educator

Problem 29

Suppose that two systems, each composed of two particles represented by circles, have 20 J of total energy. Which system, A or B, has the greater entropy? Why?

Linhan Y.
Numerade Educator

Problem 30

Suppose two systems, each composed of three particles represented by circles, have 30 J of total energy. In how many energetically equivalent ways can you distribute the particles in each system? Which system has greater entropy?

KC
Kevin C.
Numerade Educator

Problem 31

Calculate the change in entropy that occurs in the system when 1.00 mole of isopropyl alcohol (C3H8O) melts at its melting point (-89.5 C). See Table 11.9 for heats of fusion.

Aadit S.
Numerade Educator

Problem 32

Calculate the change in entropy that occurs in the system when 1.00 mole of diethyl ether (C4H10O) condenses from a gas to a liquid at its normal boiling point (34.6 C). See Table 11.7 for heats of vaporization.

KC
Kevin C.
Numerade Educator

Problem 33

Calculate the change in entropy that occurs in the system when 45.0 g of acetone (C3H6O) freezes at its melting point (-94.8 C). See Table 11.9 for heats of fusion.

Aadit S.
Numerade Educator

Problem 34

Calculate the change in entropy that occurs in the system when 55.0 g of water vaporizes from a liquid to a gas at its boiling point (100.0 C). See Table 11.7 for heats of vaporization.

KC
Kevin C.
Numerade Educator

Problem 35

Without doing any calculations, determine the sign of Ssys for each chemical reaction.

Aadit S.
Numerade Educator

Problem 36

Without doing any calculations, determine the sign of Ssys for each chemical reaction.

KC
Kevin C.
Numerade Educator

Problem 37

Without doing any calculations, determine the sign of Ssys and Ssurr for each chemical reaction. In addition, predict under what temperatures (all temperatures, low temperatures, or high temperatures), if any, the reaction is spontaneous.

Linhan Y.
Numerade Educator

Problem 38

Without doing any calculations, determine the sign of Ssys and Ssurr for each chemical reaction. In addition, predict under what temperatures (all temperatures, low temperatures, or high temperatures), if any, the reaction is spontaneous.

KC
Kevin C.
Numerade Educator

Problem 39

Calculate Ssurr at the indicated temperature for each reaction.

Aadit S.
Numerade Educator

Problem 40

A reaction has Hrxn = -112 kJ and Srxn = 354 J>K. At what temperature is the change in entropy for the reaction equal to the change in entropy for the surroundings?

KC
Kevin C.
Numerade Educator

Problem 41

Given the values of Hrxn, Srxn, and T, determine Suniv and predict whether each reaction is spontaneous. (Assume that all reactants and products are in their standard states.)

Linhan Y.
Numerade Educator

Problem 42

Given the values of Hrxn, Srxn, and T, determine Suniv and predict whether each reaction is spontaneous. (Assume that all reactants and products are in their standard states.)

David C.
Numerade Educator

Problem 43

Calculate the change in Gibbs free energy for each set of Hrxn, Srxn, and T given in Problem 41. Predict whether each reaction is spontaneous at the temperature indicated. (Assume that all reactants and products are in their standard states.)

Linhan Y.
Numerade Educator

Problem 44

Calculate the change in Gibbs free energy for each set of Hrxn, Srxn, and T given in Problem 42. Predict whether each reaction is spontaneous at the temperature indicated. (Assume that all reactants and products are in their standard states.)

KC
Kevin C.
Numerade Educator

Problem 45

Calculate the free energy change for this reaction at 25 C. Is the reaction spontaneous?

Linhan Y.
Numerade Educator

Problem 46

Calculate the free energy change for this reaction at 25 C. Is the reaction spontaneous? (Assume that all reactants and products are in their standard states.)

David C.
Numerade Educator

Problem 47

Fill in the blanks in the table. Both H and S refer to the system.

Linhan Y.
Numerade Educator

Problem 48

Predict the conditions (high temperature, low temperature, all temperatures, or no temperatures) under which each reaction is spontaneous.

KC
Kevin C.
Numerade Educator

Problem 49

How does the molar entropy of a substance change with increasing temperature?

Linhan Y.
Numerade Educator

Problem 50

What is the molar entropy of a pure crystal at 0 K? What is the significance of the answer to this question?

KC
Kevin C.
Numerade Educator

Problem 51

For each pair of substances, choose the one that you expect to have the higher standard molar entropy (S) at 25 C. Explain the reasons for your choices.

Aadit S.
Numerade Educator

Problem 52

For each pair of substances, choose the one that you expect to have the higher standard molar entropy (S) at 25 C. Explain the reasons for your choices.

KC
Kevin C.
Numerade Educator

Problem 53

Rank each set of substances in order of increasing standard molar entropy (S). Explain your reasoning.

Aadit S.
Numerade Educator

Problem 54

Rank each set of substances in order of increasing standard molar entropy (S). Explain your reasoning.

KC
Kevin C.
Numerade Educator

Problem 55

Use data from Appendix IIB to calculate Srxn for each of the reactions. In each case, try to rationalize the sign of S rxn.

Aadit S.
Numerade Educator

Problem 56

Use data from Appendix IIB to calculate Srxn for each of the reactions. In each case, try to rationalize the sign of Hrxn.

KC
Kevin C.
Numerade Educator

Problem 57

Find S for the formation of CH2Cl2(g) from its gaseous elements in their standard states. Rationalize the sign of S.

Aadit S.
Numerade Educator

Problem 58

Find S for the reaction between nitrogen gas and fluorine gas to form nitrogen trifluoride gas. Rationalize the sign of S.

KC
Kevin C.
Numerade Educator

Problem 59

Methanol burns in oxygen to form carbon dioxide and water. Write a balanced equation for the combustion of liquid methanol and calculate Hrxn, Srxn, and Grxn at 25 C. Is the combustion
of methanol spontaneous?

Aadit S.
Numerade Educator

Problem 60

In photosynthesis, plants form glucose (C6H12O6) and oxygen from carbon dioxide and water. Write a balanced equation for photosynthesis and calculate Hrxn, Srxn, and Grxn at 25 C. Is photosynthesis spontaneous?

KC
Kevin C.
Numerade Educator

Problem 61

For each reaction, calculate Hrxn, Srxn, and Grxn at 25 C and state whether the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous?
If so, should the temperature be raised or lowered from 25 C?

Aadit S.
Numerade Educator

Problem 62

For each reaction, calculate Hrxn, Srxn, and Grxn at 25 C and state whether the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous?
If so, should the temperature be raised or lowered from 25 C?

KC
Kevin C.
Numerade Educator

Problem 63

Use standard free energies of formation to calculate G at 25 C for each reaction in Problem 61. How do the values of G calculated this way compare to those calculated from H and S? Which of the two methods could be used to determine how G changes with temperature?

Aadit S.
Numerade Educator

Problem 64

Use standard free energies of formation to calculate G at 25 C for each reaction in Problem 62. How well do the values of G calculated this way compare to those calculated from H and S? Which of the two methods could be used to determine how G changes with temperature?

KC
Kevin C.
Numerade Educator

Problem 65

Consider the reaction:

Estimate G for this reaction at each temperature and predict whether the reaction is spontaneous. (Assume that H and S do not change too much within the given temperature range.)

a. 298 K b. 715 K c. 855 K

Aadit S.
Numerade Educator

Problem 66

Consider the reaction:

Estimate G for this reaction at each temperature and predict whether the reaction is spontaneous. (Assume that H and S do not change too much within the given temperature range.)

a. 298 K b. 1055 K c. 1455 K

KC
Kevin C.
Numerade Educator

Problem 67

Determine G for the reaction:

Use the following reactions with known Grxn values:

Aadit S.
Numerade Educator

Problem 68

Calculate Grxn for the reaction:

Use the following reactions and given Grxn values:

KC
Kevin C.
Numerade Educator

Problem 69

Consider the sublimation of iodine at 25.0 C :

a. Find Grxn at 25.0 C.

b. Find Grxn at 25.0 C under the following nonstandard conditions:
i. PI2 = 1.00 mmHg
ii. PI2 = 0.100 mmHg

c. Explain why iodine spontaneously sublimes in open air at 25 C.

Aadit S.
Numerade Educator

Problem 70

Consider the evaporation of methanol at 25.0 C.

a. Find Grxn at 25.0 C.

b. Find Grxn at 25.0 C under the following nonstandard conditions:
i. PCH3OH = 150.0 mmHg
ii. PCH3OH = 100.0 mmHg
iii. PCH3OH = 10.0 mmHg

c. Explain why methanol spontaneously evaporates in open air at 25.0 C.

KC
Kevin C.
Numerade Educator

Problem 71

Consider the reaction:

Calculate G for this reaction at 25 C under the following conditions:

Aadit S.
Numerade Educator

Problem 72

Consider the reaction:

Calculate G for this reaction at 25 C under the following conditions:

KC
Kevin C.
Numerade Educator

Problem 73

Use data from Appendix IIB to calculate the equilibrium constant at 25 C for each reaction.

a. 2 CO(g) + O2(g)2 CO2(g)
b. 2 H2S(g)2 H2(g) + S2(g)

Aadit S.
Numerade Educator

Problem 74

Use data from Appendix IIB to calculate the equilibrium constant at 25 C for each reaction. Gf for BrCl(g) is -1.0 kJ>mol.

a. 2 NO2(g)N2O4(g)
b. Br2(g) + Cl2(g)2 BrCl(g)

David C.
Numerade Educator

Problem 75

Consider the reaction:

Calculate Grxn for the reaction at 25 C under the following conditions:

a. standard conditions
b. at equilibrium
c. PCH3OH = 1.0 atm; PCO = PH2 = 0.010 atm

Aadit S.
Numerade Educator

Problem 76

Consider the reaction:

Calculate Grxn for the reaction at 25 C under the following conditions:

a. standard conditions
b. at equilibrium
c. PICl = 2.55 atm; PI2 = 0.325 atm; PCl2 = 0.221 atm

KC
Kevin C.
Numerade Educator

Problem 77

Estimate the value of the equilibrium constant at 525 K for each reaction in Problem 73.

Ronald P.
Numerade Educator

Problem 78

Estimate the value of the equilibrium constant at 655 K for each reaction in Problem 74. (H f for BrCl is 14.6 kJ>mol.)

KC
Kevin C.
Numerade Educator

Problem 79

Consider the reaction:

The following data show the equilibrium constant for this reaction measured at several different temperatures. Use the data to find Hrxn and Srxn for the reaction.

Aadit S.
Numerade Educator

Problem 80

Consider the reaction:

The following data show the equilibrium constant for this reaction measured at several different temperatures. Use the data to find Hrxn and Srxn for the reaction.

KC
Kevin C.
Numerade Educator

Problem 81

The change in enthalpy (Hrxn) for a reaction is -25.8 kJ>mol. The equilibrium constant for the reaction is 1.4 * 103 at 298 K. What is the equilibrium constant for the reaction at 655 K?

Aadit S.
Numerade Educator

Problem 82

A reaction has an equilibrium constant of 8.5 * 103 at 298 K. At 755 K, the equilibrium constant is 0.65. Find Hrxn for the reaction.

KC
Kevin C.
Numerade Educator

Problem 83

Determine the sign of Ssys for each process.
a. water boiling
b. water freezing

Linhan Y.
Numerade Educator

Problem 84

Determine the sign of Ssys for each process.
a. dry ice subliming
b. dew forming

KC
Kevin C.
Numerade Educator

Problem 85

Our atmosphere is composed primarily of nitrogen and oxygen, which coexist at 25 C without reacting to any significant extent. However, the two gases can react to form nitrogen monoxide according to the reaction:

a. Calculate G and Kp for this reaction at 298 K. Is the reaction spontaneous?
b. Estimate G at 2000 K. Does the reaction become more spontaneous as temperature increases?

Aadit S.
Numerade Educator

Problem 86

Nitrogen dioxide, a pollutant in the atmosphere, can combine with water to form nitric acid. One of the possible reactions is shown here. Calculate G and Kp for this reaction at 25 C and comment on the spontaneity of the reaction.

KC
Kevin C.
Numerade Educator

Problem 87

Ethene (C2H4) can be halogenated by the reaction:

where X2 can be Cl2, Br2, or I2. Use the thermodynamic data given to calculate H, S, G, and Kp for the halogenation reaction by each of the three halogens at 25 C. Which reaction is most spontaneous? Least spontaneous? What is the main factor responsible for the difference in the spontaneity of the three
reactions? Does higher temperature make the reactions more spontaneous or less spontaneous?

Check back soon!

Problem 88

H2 reacts with the halogens (X2) according to the reaction:

where X2 can be Cl2, Br2, or I2. Use the thermodynamic data in Appendix IIB to calculate H, S, G, and Kp for the reaction between hydrogen and each of the three halogens. Which reaction is most spontaneous? Least spontaneous? What is the main factor responsible for the difference in the spontaneity of the three reactions? Does higher temperature make the reactions more spontaneous or less spontaneous?

Aadit S.
Numerade Educator

Problem 89

Consider this reaction occurring at 298 K:

a. Show that the reaction is not spontaneous under standard conditions by calculating Grxn.

b. If a reaction mixture contains only N2O and NO2 at partial pressures of 1.0 atm each, the reaction will be spontaneous until some NO forms in the mixture. What maximum partial pressure of NO builds up before the reaction ceases to be spontaneous?

c. Can the reaction be made more spontaneous by an increase or decrease in temperature? If so, what temperature is required to make the reaction spontaneous under standard conditions?

Aadit S.
Numerade Educator

Problem 90

Consider this reaction occurring at 298 K:

a. Show that the reaction is not spontaneous under standard conditions by calculating Grxn.

b. If BaCO3 is placed in an evacuated flask, what is the partial pressure of CO2 when the reaction reaches equilibrium?

c. Can the reaction be made more spontaneous by an increase or decrease in temperature? If so, at what temperature is the partial pressure of carbon dioxide 1.0 atm?

Aadit S.
Numerade Educator

Problem 91

Living organisms use energy from the metabolism of food to create an energy-rich molecule called adenosine triphosphate (ATP). The ATP then acts as an energy source for a variety of reactions that the living organism must carry out to survive. ATP provides energy through its hydrolysis, which can be symbolized as follows:

where ADP represents adenosine diphosphate and Pi represents an inorganic phosphate group (such as HPO42-).

a. Calculate the equilibrium constant, K, for the given reaction at 298 K.

b. The free energy obtained from the oxidation (reaction with oxygen) of glucose (C6H12O6) to form carbon dioxide and water can be used to re-form ATP by driving the given reaction in reverse. Calculate the standard free energy change for the oxidation of glucose and estimate the maximum number of moles of ATP that can be formed by the oxidation of one mole of glucose.

Aadit S.
Numerade Educator

Problem 92

The standard free energy change for the hydrolysis of ATP was given in Problem 91. In a particular cell, the concentrations of ATP, ADP, and Pi are 0.0031 M, 0.0014 M, and 0.0048 M, respectively. Calculate the free energy change for the hydrolysis of ATP under these conditions. (Assume a temperature of 298 K.)

Ronald P.
Numerade Educator

Problem 93

These reactions are important in catalytic converters in automobiles. Calculate G for each at 298 K. Predict the effect of increasing temperature on the magnitude of G.
a. 2 CO(g) + 2 NO(g)-N2(g) + 2 CO2(g)
b. 5 H2(g) + 2 NO(g)-2 NH3(g) + 2 H2O(g)
c. 2 H2(g) + 2 NO(g)-N2(g) + 2 H2O(g)
d. 2 NH3(g) + 2 O2(g)-N2O(g) + 3 H2O(g)

Aadit S.
Numerade Educator

Problem 94

Calculate G at 298 K for these reactions and predict the effect on G of lowering the temperature.

a. NH3(g) + HBr(g)-NH4Br(s)
b. CaCO3(s)-CaO(s) + CO2(g)
c. CH4(g) + 3 Cl2(g)-CHCl3(g) + 3 HCl(g)
(G f for CHCl3(g) is -70.4 kJ>mol.)

KC
Kevin C.
Numerade Educator

Problem 95

All the oxides of nitrogen have positive values of Gf at 298 K, but only one common oxide of nitrogen has a positive Sf . Identify that oxide of nitrogen without reference to thermodynamic data and explain.

Aadit S.
Numerade Educator

Problem 96

The values of Gf for the hydrogen halides become less negative with increasing atomic number. The Gf of HI is slightly positive. On the other hand, the trend in Sf is to become more positive with increasing atomic number. Explain.

Ronald P.
Numerade Educator

Problem 97

Consider the reaction X2(g)-2 X(g). When a vessel initially containing 755 torr of X2 comes to equilibrium at 298 K, the equilibrium partial pressure of X is 103 torr. The same reaction is repeated with an initial partial pressure of 748 torr of X2 at 755 K; the equilibrium partial pressure of X is 532 torr. Find H
for the reaction.

Aadit S.
Numerade Educator

Problem 98

Dinitrogen tetroxide decomposes to nitrogen dioxide:

At 298 K, a reaction vessel initially contains 0.100 atm of N2O4. When equilibrium is reached, 58% of the N2O4 has decomposed to NO2. What percentage of N2O4 decomposes at 388 K? Assume that the initial pressure of N2O4 is the same (0.100 atm).

David C.
Numerade Educator

Problem 99

Indicate and explain the sign of Suniv for each process.
a. 2 H2(g) + O2(g)-2 H2O(l) at 298 K
b. the electrolysis of H2O(l) to H2(g) and O2(g) at 298 K
c. the growth of an oak tree from an acorn

Aadit S.
Numerade Educator

Problem 100

The Haber process is very important for agriculture because it converts N2(g) from the atmosphere into bound nitrogen, which can be taken up and used by plants. The Haber process reaction is N2(g) + 3 H2(g)2 NH3(g). The reaction is exothermic but is carried out at relatively high temperatures. Why?

KC
Kevin C.
Numerade Educator

Problem 101

A metal salt with the formula MCl2 crystallizes from water to form a solid with the composition MCl2 # 6 H2O. The equilibrium vapor pressure of water above this solid at 298 K is 18.3 mmHg. What is the value of G for the reaction MCl2 # 6 H2O(s) MCl2(s) + 6 H2O(g) when the pressure of water vapor is 18.3
mmHg? When the pressure of water vapor is 760.0 mmHg?

Aadit S.
Numerade Educator

Problem 102

The solubility of AgCl(s) in water at 25 C is 1.33 * 10-5 mol>L, and its H of solution is 65.7 k>mol. What is its solubility at 50.0 C?

KC
Kevin C.
Numerade Educator

Problem 103

Review the subsection in this chapter entitled Making a Nonspontaneous Process Spontaneous in Section 18.8. The hydrolysis of ATP, shown in Problem 91, is often used to drive nonspontaneous processes-such as muscle contraction and protein synthesis-in living organisms. The nonspontaneous process to be driven must be coupled to the ATP hydrolysis reaction. For example, suppose the nonspontaneous process is A + B-AB (G positive). The coupling of a nonspontaneous
reaction such as this one to the hydrolysis of ATP is often accomplished by the mechanism:

a. Calculate K for the reaction between glutamate and ammonia. (The standard free energy change for the reaction is +14.2 kJ>mol. Assume a temperature of 298 K.)

b. Write a set of reactions such as those given showing how the glutamate and ammonia reaction can couple with the hydrolysis of ATP. What is G rxn and K for the coupled reaction?

Aadit S.
Numerade Educator

Problem 104

Calculate the entropy of each state and rank the states in order of increasing entropy.

David C.
Numerade Educator

Problem 105

Suppose we redefine the standard state as P = 2 atm. Find the new standard Gf values of each substance.
a. HCl(g)
b. N2O(g)
c. H(g)
Explain the results in terms of the relative entropies of reactants and products of each reaction.

Aadit S.
Numerade Educator

Problem 106

The G for the freezing of H2O(l) at -10 C is -210 J>mol, and the heat of fusion of ice at this temperature is 5610 J>mol. Find the entropy change of the universe when 1 mol of water freezes at -10 C.

KC
Kevin C.
Numerade Educator

Problem 107

Consider the reaction that occurs during the Haber process:

The equilibrium constant is 3.9 * 105 at 300 K and 1.2 * 10-1 at 500 K. Calculate Hrxn and Srxn for this reaction.

Aadit S.
Numerade Educator

Problem 108

The salt ammonium nitrate can follow three modes of decomposition: (a) to HNO3(g) and NH3(g), (b) to N2O(g) and H2O(g), and (c) to N2(g), O2(g), and H2O(g). Calculate Grxn for each mode of decomposition at 298 K. Explain in light of these results how it is still possible to use ammonium nitrate as a fertilizer and the precautions that should be taken when it is used.

Aadit S.
Numerade Educator

Problem 109

Given the tabulated data, calculate Svap for each of the first four liquids. (Svap = Hvap>T, where T is in K)

All four values should be close to each other. Predict whether the last two liquids in the table have Svap in this same range. If not, predict whether it is larger or smaller and explain. Verify your prediction.

Aadit S.
Numerade Educator

Problem 110

Which statement is true?
a. A spontaneous reaction is always a fast reaction.
b. A spontaneous reaction is always a slow reaction.
c. The spontaneity of a reaction is not necessarily related to the speed of a reaction.

KC
Kevin C.
Numerade Educator

Problem 111

Which process is necessarily driven by an increase in the entropy of the surroundings?
a. the condensation of water
b. the sublimation of dry ice
c. the freezing of water

Aadit S.
Numerade Educator

Problem 112

Consider the changes in the distribution of nine particles into three interconnected boxes shown here. Which has the most negative S?

KC
Kevin C.
Numerade Educator

Problem 113

Which statement is true?
a. A reaction in which the entropy of the system increases can be spontaneous only if it is exothermic.
b. A reaction in which the entropy of the system increases can be spontaneous only if it is endothermic.
c. A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic.

Aadit S.
Numerade Educator

Problem 114

Which process is spontaneous at 298 K?
a. H2O(l)-H2O(g, 1 atm)
b. H2O(l)-H2O(g, 0.10 atm)
c. H2O(l)-H2O(g, 0.010 atm)

Ronald P.
Numerade Educator

Problem 115

The free energy change of the reaction A(g)-B(g) is zero under certain conditions. The standard free energy change of the reaction is -42.5 kJ. Which statement must be true about the reaction?
a. The concentration of the product is greater than the concentration of the reactant.
b. The reaction is at equilibrium.
c. The concentration of the reactant is greater than the concentration of the product.

Aadit S.
Numerade Educator

Problem 116

The reaction A(g)-B(g) has an equilibrium constant of 5.8and under certain conditions has Q = 336. What can you conclude about the sign of Grxn and Grxn for this reaction under these conditions?

KC
Kevin C.
Numerade Educator

Problem 117

Imagine that you roll two dice. Write down all the possible rolls that sum to 2. Write all the possible rolls that sum to 12. Write all the possible rolls that sum to 7. Which configuration has the greatest entropy: 2, 12, or 7?

Aadit S.
Numerade Educator

Problem 118

If you roll one million dice, what will be the average of all the dice? If there is a room with one million dice and they all have a 1 on the top face, and there is an earthquake strong enough to roll dice around, what is the likelihood that after the earthquake all the top faces will sum to one million? To six million? How
does this thought experiment illustrate the second law of thermodynamics?

Aadit S.
Numerade Educator

Problem 119

Not all processes in which the system increases in entropy are spontaneous. How can this observation be consistent with the second law? Provide an example and explain your answer in complete sentences.

Aadit S.
Numerade Educator

Problem 120

Have each group member look up Hf and S for one substance in the reaction: 3 O2(g) + 6 H2(g) + 6 C(s, graphite)-C6H12O6(s, glucose). What is H for this reaction? What is S? When is Hf for a substance equal to zero? When is S for a substance equal to zero?

KC
Kevin C.
Numerade Educator

Problem 121

Calculate G at 25 C for the reaction in the previous question. Is this reaction spontaneous under standard conditions? How do you know? What is the determining factor: the change in energy or the change in entropy or both? Explain.

Aadit S.
Numerade Educator

Problem 122

Borax, sodium tetraborate decahydrate, is an important mineral found in dry lakebeds in California. It is used to make soap and glass, and used as a preservative. You can use the values of Ksp of borax at different temperatures to determine H, S, and G for the dissolution of borax:

has the form of a linear equation y = mx + b, where y is the ln Ksp and x is 1/T. The slope is equal to (H/R), and the y intercept is S/R, where R is the gas constant, 8.314 J/K mol. If you measure Ksp at several different temperatures, you can plot the ln K versus 1/T (T in kelvin) as shown here.

Aadit S.
Numerade Educator