Deck 9: Thermochemistry: Chemical Energy

Question 1

For a particular process that is carried out at constant pressure,q = 200 kJ and w = -85 kJ.Therefore,

A)ΔE = 115 kJ and ΔH = 200 kJ.
B)ΔE = 200 kJ and ΔH = 115 kJ.
C)ΔE = 200 kJ and ΔH = 285 kJ.
D)ΔE = 285 kJ and ΔH = 200 kJ.

Answer 1

ΔE = 115 kJ and ΔH = 200 kJ.

Question 2

An ideal gas expands into a vacuum (external pressure = 0)without gaining or losing heat.For this expansion

A)ΔE increases.
B)ΔE does not change.
C)ΔE decreases.
D)ΔE = TΔS.

Answer 2

ΔE does not change.

Question 3

A process is carried out at constant pressure.Given that ΔE is positive and ΔH is negative,

A)the system absorbs heat and expands during the process.
B)the system absorbs heat and contracts during the process.
C)the system loses heat and expands during the process.
D)the system loses heat and contracts during the process.

Answer 3

the system loses heat and contracts during the process.

Question 4

For most chemical reactions

A)ΔH is much larger than ΔE.
B)ΔE is much larger than ΔH.
C)ΔH is equal to ΔE.
D)the difference between ΔH and ΔE is very small.

Question 5

In which case is the work done on the system always positive?

A)ΔE > 0
B)ΔV > 0
C)ΔV = 0
D)ΔV < 0

Question 6

For an explosion in an open vessel,one would expect

A)ΔH to be positive and ΔE to be less than ΔH.
B)ΔH to be positive and ΔE to be greater than ΔH.
C)ΔH to be negative and ΔE to be less than ΔH.
D)ΔH to be negative and ΔE to be greater than ΔH.

Question 7

Which of the following states the first law of thermodynamics (conservation of energy)?

A)w = -PΔV
B)ΔE_system = -ΔE_surroundings
C)ΔH = ΔE + PΔV
D)q = smΔT

Question 8

Most chemical reactions are carried out in one of two ways: I.in an open vessel at constant atmospheric pressure
II.in a closed vessel
Which is true?

A)ΔH = q for condition I and ΔE = q for condition II.
B)ΔE = q for condition I and ΔH = q for condition II.
C)ΔH = w for condition I and ΔE = w for condition II.
D)ΔE = w for condition I and ΔH = w for condition II.

Question 9

What is expected when the reaction shown below takes place in a thermally-insulated container outfitted with a movable piston at a constant atmospheric pressure of 1 atm? 2 C₂H₆(g)+ 7 O₂(g)→ 4 CO₂(g)+ 6 H₂O(g)

A)Volume will decrease and work will be done by the system.
B)Volume will decrease and work will be done on the system.
C)Volume will increase and work will be done by the system.
D)Volume will increase and work will be done on the system.

Question 10

At constant pressure for the reaction shown below,what can be said about PΔV and ΔE? N₂(g)+ 3 H₂(g)→ 2 NH₃(g)ΔH° = - 92.2 kJ

A)PΔV > 0 and ΔE > -92.2 kJ
B)PΔV > 0 and ΔE < -92.2 kJ
C)PΔV < 0 and ΔE > -92.2 kJ
D)PΔV < 0 and ΔE < -92.2 kJ

Question 11

Under thermodynamic standard state conditions the element oxygen occurs as

A)O(g)
B)O₂(g)
C)O₂(l)
D)O₃(g)

Question 12

For a process at constant volume,

A)q = 0,w = 0,and ΔE = 0.
B)w = 0 and ΔE = q.
C)w = 0 and ΔH = q.
D)w = 0 and ΔE = ΔH.

Question 13

A process is carried out at constant pressure.Given that 0 > ΔH > ΔE,

A)the system absorbs heat and expands during the process.
B)the system absorbs heat and contracts during the process.
C)the system loses heat and expands during the process.
D)the system loses heat and contracts during the process.

Question 14

For a process at constant pressure,

A)ΔE = w and q = 0.
B)ΔE = q and w = 0.
C)ΔE = ΔH.
D)ΔH = q.

Question 15

Find ΔE° for the reaction below if the process is carried out at a constant pressure of 1.00 atm and ΔV (the volume change)= -24.5 L.(1 L ∙ atm = 101 J) 2 CO(g)+ O₂ (g)→ 2 CO₂(g)ΔH° = -566.kJ

A)+2.47 kJ
B)-2.47 kJ
C)-564 kJ
D)-568 kJ

Question 16

Calculate the work energy,w,gained or lost by the system when a gas expands from 20 L to 35 L against a constant external pressure of 2.0 atm.[1 L ∙ atm = 101 J]

A)-5.3 kJ
B)-3.0 kJ
C)+3.0 kJ
D)+5.3 kJ

Question 17

When 10.0 mol of benzene is vaporized at a constant pressure of 1.00 atm and at its normal boiling point of 80.1°C,339 kJ are absorbed and PΔV for the vaporization process is equal to 29.0 kJ,then

A)ΔE = 310.kJ and ΔH = 339.kJ.
B)ΔE = 368.kJ and ΔH = 339.kJ.
C)ΔE = 339.kJ and ΔH = 310.kJ.
D)ΔE = 339.kJ and ΔH = 368.kJ.

Question 18

Which is a measure of the sum of the kinetic and potential energies of each particle in the system?

A)E,the internal energy
B)G,the Gibbs free energy
C)H,the enthalpy
D)T,the temperature

Question 19

Which depends only on the initial and final state?

A)q
B)w
C)q + w
D)q - w

Question 20

When 20.00 moles of H₂(g)reacts with 10.00 mol of O₂(g)to form 20.00 mol of H₂O(l)at 25°C and a constant pressure of 1.00 atm.If 1366 kJ of heat are released during this reaction,and PΔV is equal to -74.00 kJ,then

A)ΔH° = +1366 kJ and ΔE° = +1440 kJ.
B)ΔH° = +1366 kJ and ΔE° = +1292 kJ.
C)ΔH° = -1366 kJ and ΔE° = -1292 kJ.
D)ΔH° = -1366 kJ and ΔE° = -1440 kJ.

Question 21

At constant pressure,the combustion of 30.00 g of C₂H₆(g)releases 1560 kJ of heat.What is ΔH for the reaction given below? 2 C₂H₆(g)+ 7 O₂(g)→ 4 CO₂(g)+ 6 H₂O(l)

A)-43.2 kJ
B)-779 kJ
C)-1560 kJ
D)-3120 kJ

Question 22

At 25°C the heat of fusion of aluminum is 10.6 kJ/mol and the heat of sublimation is 326.4 kJ/mol.What is the heat of vaporization of aluminum at 25°C?

A)158.2 kJ/mol
B)168.5 kJ/mol
C)315.8 kJ/mol
D)337.0 kJ/mol

Question 23

When 0.700 g of anthracene,C₁₄H₁₀,is combusted in a bomb calorimeter that has a water jacket containing 500.g of water,the temperature of the water increases by 13.27°C.Assuming that the specific heat of water is 4.18 J/(g ∙ °C),and that the heat absorption by the calorimeter is negligible,estimate the enthalpy of combustion per mole of anthracene.

A)+39.7 kJ/mol
B)-39.7 kJ/mol
C)-7060 kJ/mol
D)-8120 kJ/mol

Question 24

When 2.500 mol of CH₄(g)reacts with excess Cl₂(g)at constant pressure according to the chemical equation shown below,1770.kJ of heat are released.Calculate the value of ΔH for this reaction,as written. 2 CH₄(g)+ 3 Cl₂(g)→ 2 CHCl₃(l)+ 3 H₂(g)ΔH = ?

A)-1416 kJ
B)-708.0 kJ
C)+708.0 kJ
D)+1416 kJ

Question 25

Which is the most exothermic reaction?

A)CH₄(g)+ 2 O₂(g)→ CO₂(g)+ 2 H₂O(g)
B)CH₄(g)+ 2 O₂(g)→ CO₂(g)+ 2 H₂O(l)
C)CO₂(g)+ 2 H₂O(l)→CH₄(g)+ 2 O₂(g)
D)CO₂(g)+ 2 H₂O(g)→CH₄(g)+ 2 O₂(g)

Question 26

The enthalpy of fusion,or heat of fusion (ΔH_fusion),of water is positive and corresponds to which physical change?

A)H₂O(g)→ H₂O(s)
B)H₂O(l)→ H₂O(s)
C)H₂O(s)→ H₂O(l)
D)H₂O(s)→ H₂O(g)

Question 27

Sodium metal reacts with water to produce hydrogen gas and sodium hydroxide according to the chemical equation shown below.When 0.0500 mol of Na is added to 100.00 g of water,the temperature of the resulting solution rises from 25.00°C to 46.23°C.If the specific heat of the solution is 4.18 J/(g ∙ °C),calculate ΔH for the reaction,as written. 2 Na(s)+ 2 H₂O(l)→ 2 NaOH(aq)+ H₂(g)ΔH = ?

A)-5.41 kJ
B)-90.0 kJ
C)-180 kJ
D)-362 kJ

Question 28

Water has an unusually high

A)electrical conductivity.
B)heat of combustion.
C)heat of formation.
D)specific heat.

Question 29

In the lab,you mix two solutions (each originally at the same temperature)and the temperature of the resulting solution decreases.Which of the following is true?

A)The chemical reaction is releasing energy.
B)The energy released is equal to s × m × ΔT.
C)The chemical reaction is absorbing energy.
D)The chemical reaction is exothermic.

Question 30

When 50.0 mL of 0.400 M Ca(NO₃)₂ is added to 50.0 mL of 0.800 M NaF,CaF₂ precipitates,as shown in the net ionic equation below.The initial temperature of both solutions is 30.00°C.Assuming that the reaction goes to completion,and that the resulting solution has a mass of 100.00 g and a specific heat of 4.18 J/(g ∙ °C),calculate the final temperature of the solution. Ca²⁺(aq)+ 2 F^-(aq)→ CaF₂(s)ΔH° = -11.5 kJ

A)29.45°C
B)30.55°C
C)31.10°C
D)31.65°C

Question 31

Calculate the total quantity of heat required to convert 50.0 g of liquid CCl₄(l)from 25.0°C to gaseous CCl₄ at 76.8°C (the normal boiling point for CCl₄)? The specific heat of CCl₄(l)is 0.857 J/(g ∙ °C),its heat of fusion is and its heat of vaporization is

A)2.22 kJ
B)3.28 kJ
C)11.91 kJ
D)12.98 kJ

Question 32

At 1 atm pressure the heat of sublimation of gallium is 277 kJ/mol and the heat of vaporization is 271 kJ/mol.How much heat is required to melt 0.500 mol of gallium at 1.00 atm pressure?

A)6.00 kJ
B)3.00 kJ
C)268 kJ
D)271 kJ

Question 33

When 8.00 g of Ba(s)is added to 100.00 g of water in a container open to the atmosphere,the reaction shown below occurs and the temperature of the resulting solution rises from 22.00°C to 77.62°C.If the specific heat of the solution is 4.18 J/(g ∙ °C),calculate ΔH for the reaction,as written. Ba(s)+ 2 H₂O(l)→ Ba(OH)₂(aq)+ H₂(g)ΔH = ?

A)-431 kJ
B)-3.14 kJ
C)3.14 kJ
D)431 kJ

Question 34

It takes 15.5 kJ of energy to raise the temperature of 200 g of benzene from 25.0°C to 70.0°C.What is the specific heat of benzene?

A)1.10 J/(g ∙ °C)
B)1.72 J/(g ∙ °C)
C)3.48 J/(g ∙ °C)
D)5.41 J/(g ∙ °C)

Question 35

How much heat is absorbed/released when 10.00 g of NH₃(g)reacts in the presence of excess O₂(g)to produce NO(g)and H₂O(l)according to the following chemical equation? 4 NH₃(g)+ 5 O₂(g)→ 4 NO(g)+ 6 H₂O(l)ΔH° = +1168 kJ

A)171.5 kJ of heat are absorbed.
B)171.5 kJ of heat are released.
C)686.0 kJ of heat are absorbed.
D)686.0 kJ of heat are released.

Question 36

How much heat is absorbed when 20.00 g of C(s)reacts in the presence of excess SO₂(g)to produce CS₂(l)and CO(g)according to the following chemical equation? 5 C(s)+ 2 SO₂(g)→ CS₂(l)+ 4 CO(g)ΔH° = +239.9 kJ

A)79.97 kJ
B)159.9 kJ
C)399.5 kJ
D)959.3 kJ

Question 37

The specific heat of copper is 0.385 J/(g ∙ °C).If 34.2 g of copper,initially at 25°C,absorbs 7.880 kJ,what will be the final temperature of the copper?

A)25.4°C
B)27.8°C
C)598°C
D)623°C

Question 38

For the reaction I₂(g)→ I₂(s),ΔH° = -62.4 kJ at 25°C.Based on these data,at 25°C

A)ΔH°_vap = -62.4 kJ/mol.
B)ΔH°_vap = 62.4 kJ/mol.
C)ΔH°_sub = -62.4 kJ/mol.
D)ΔH°_sub = 62.4 kJ/mol.

Question 39

The heat of vaporization of water at 100°C is 40.66 kJ/mol.Calculate the quantity of heat that is absorbed/released when 20.00 g of steam condenses to liquid water at 100°C.

A)45.2 kJ of heat are absorbed.
B)45.2 kJ of heat are released.
C)813.2 kJ of heat are absorbed.
D)813.2 kJ of heat are released.

Question 40

Which of the following scenarios involves a transfer of heat from system to surroundings?

A)evaporating rubbing alcohol from your skin
B)solidifying molten gold into a gold bar
C)melting solid gallium metal with heat from your hand
D)none of these

Question 41

The values of ΔH°_f for the three states of benzene are approximately -22 kcal/mol,-11 kcal/mol,and Which is the value for solid benzene?

A)-22 kcal/mol
B)-11 kcal/mol
C)20 kcal/mol
D)cannot be determined without additional information

Question 42

Heat of formation for CO is -110.5 KJ/mol and the heat of formation for MgO is -602 KJ/mol.Which of the following statements is true?

A)The bond in CO is stronger than the bond in MgO.
B)The bond in MgO is stronger than the bond in CO.
C)The bonds in MgO and CO are equally strong.
D)Impossible to determine to given data.

Question 43

Two metals of equal mass with different heat capacities are subjected to the same amount of heat.Which undergoes the smallest change in temperature?

A)The metal with the highest heat capacity.
B)The metal with the lowest heat capacity.
C)Both undergo the same change in temperature.
D)You need to know the initial temperatures of both metals.

Question 44

Given that ΔH°= -311 kJ for the hydrogenation of acetylene,C₂H₂: H-C C-H(g)+ 2 H₂(g)→ CH₃-CH₃(g)
And the following bond dissociation energies,estimate a value for the C-to-C triple bond dissociation energy.

A)1050 kJ/mol
B)833 kJ/mol
C)807 kJ/mol
D)397 kJ/mol

Question 45

For the reaction 2CH₄ (g)+ 3 Cl₂ (g)→ 2 CHCl₃ (l)+ 3 H₂ (g),ΔH° = -118.6 kJ. ΔH°_f = -134.1 kJ/mol for CHCl₃ (l).Find ΔH°_f for CH₄ (g).

A)-193.4 kJ/mol
B)-74.8 kJ/mol
C)74.8 kJ/mol
D)193.4 kJ/mol

Question 46

Ethyl alcohol is produced by the fermentation of glucose,C₆H₁₂O₆. C₆H₁₂O₆(s)→ 2 C₂H₅OH(l)+ 2 CO₂(g)ΔH° = -69.1 kJ
Given that the enthalpy of formation is -277.7 kJ/mol for C₂H₅OH(l)and -393.5 kJ/mol for CO₂(g),find the enthalpy of formation for C₆H₁₂O₆.

A)-1411.5 kJ/mol
B)-1273.3 kJ/mol
C)-740.3 kJ/mol
D)-602.1 kJ/mol

Question 47

Determine the sign of ΔS° for each of the following: I.C₆H₆(s)→ C₆H₆(l)
II.2 SO₂(g)+ O₂(g)→ 2 SO₃(g)

A)ΔS° should be negative for I and negative for II.
B)ΔS° should be negative for I and positive for II.
C)ΔS° should be positive for I and negative for II.
D)ΔS° should be positive for I and positive for II.

Question 48

Use the given average bond dissociation energies,D,to estimate ΔH for the reaction of methane,CH₄(g),with fluorine according to the equation: CH₄(g)+ 2 F₂(g)→ CF₄(g)+ 2 H₂(g)

A)-716 kJ
B)-318 kJ
C)+318 kJ
D)+716 kJ

Question 49

The heat of combustion per mole for acetylene,C₂H₂(g),is -1299.5 kJ/mol.Assuming that the combustion products are CO₂(g)and H₂O(l),and given that the enthalpy of formation is -393.5 kJ/mol for CO₂(g)and -285.8 kJ/mol for H₂O(l),find the enthalpy of formation of C₂H₂(g).

A)-846.1 kJ/mol
B)-620.2 kJ/mol
C)-226.7 kJ/mol
D)+226.7 kJ/mol

Question 50

Which of the following can be interpreted as a measure of randomness?

A)enthalpy
B)entropy
C)free energy
D)temperature

Question 51

Coal gasification can be represented by the equation: 2 C(s)+ 2 H₂O(g)→ CH₄(g)+ CO₂(g)ΔH = ?
Use the following information to find ΔH for the reaction above.
CO(g)+ H₂(g)→ C(s)+ H₂O(g)ΔH = -131 kJ
CO(g)+ H₂O(g)→ CO₂(g)+ H₂(g)ΔH = -41 kJ
CO(g)+ 3 H₂(g)→ CH₄(g)+ H₂O(g)ΔH = -206 kJ

A)15 kJ
B)116 kJ
C)-116 kJ
D)-372 kJ

Question 52

Find ΔH° for the reaction C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(l). ΔH° = -2046 kJ for the reaction: C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g)
The heat of vaporization of water is 44.0 kJ/mol.Note that H₂O is a liquid in the first reaction and a gas in the second.

A)-2222 kJ
B)-2090 kJ
C)-2002 kJ
D)-1870 kJ

Question 53

Which of CH₄(g),C₂H₂(g),and CH₃OH(l)provides the most energy per gram upon combustion and which provides the least? CH₄(g)+ 2 O₂(g)→ CO₂(g)+ 2 H₂O(l)ΔH° = -890 kJ
2 C₂H₂(g)+ 5 O₂(g)→ 4 CO₂(g)+ 2 H₂O(l)ΔH° = -2599 kJ
2 CH₃OH(l)+ 3 O₂(g)→ 2 CO₂(g)+ 4 H₂O(l)ΔH° = -1453 kJ

A)C₂H₂ provides the most energy per gram and CH₄ the least.
B)C₂H₂ provides the most energy per gram and CH₃OH the least.
C)CH₄ provides the most energy per gram and CH₃OH the least.
D)CH₄ provides the most energy per gram and C₂H₂ the least.

Question 54

Which thermodynamic function is most related to disorder and probability?

A)enthalpy
B)internal energy
C)entropy
D)heat capacity

Question 55

For the reaction,C₂H₂(g)→ 2 C(g)+ 2 H(g),one would expect

A)ΔH° to be negative and ΔS° to be negative.
B)ΔH° to be negative and ΔS° to be positive.
C)ΔH° to be positive and ΔS° to be negative.
D)ΔH° to be positive and ΔS° to be positive.

Question 56

Given: S (s)+ O₂ (g)→ SO₂ (g)ΔH° = -296.1 kJ 2 SO₃ (g)→ 2 SO₂ (g)+ O₂ (g)ΔH° = 198.2 kJ
Find ΔH° for : 2 S(s)+ 3 O₂(g)→ 2 SO₃(g)

A)-790.4 kJ
B)-394.0 kJ
C)-97.9 kJ
D)+97.9 kJ

Question 57

One method for making ethanol,C₂H₅OH,involves the gas-phase hydration of ethylene,C₂H₄: Estimate ΔH for this reaction from the given average bond dissociation energies,D.

A)-580 kJ
B)-35 kJ
C)+35 kJ
D)580 kJ

Question 58

Which equation represents the reaction whose ΔH,represents the standard enthalpy of formation of CHCl₃(l)at 25°C? (i.e. ,for which is ΔH = ΔH°_f of CHCl₃)

A)CHCl₃(l)→ C(s)+ H(g)+ 3 Cl(g)
B)C(s)+ H(g)+ 3 Cl(g)→ CHCl₃(l)
C)C(s)+ 1/2 H₂(g)+ 3/2 Cl₂(g)→ CHCl₃(l)
D)2 C(s)+ H₂(g)+ 3 Cl₂(g)→ 2 CHCl₃(l)

Question 59

Use the given standard enthalpies of formation to calculate ΔH° for the following reaction 3 Fe₂O₃(s)+ CO(g)→ 2 Fe₃O₄(s)+ CO₂(g).

A)-5213.4 kJ
B)-577.2 kJ
C)-47.2 kJ
D)+47.2 kJ

Question 60

Calculate the enthalpy of combustion per mole for C₆H₁₂O₆.Assume that the combustion products are CO₂(g)and H₂O(l).

A)-5336 kJ/mol
B)-2816 kJ/mol
C)-1939 kJ/mol
D)580.7 kJ/mol

Question 61

Reactant R reacts with reactant S in two steps to yield product Z.
Step (1)in the reaction is represented by

A)arrow A.
B)arrow B.
C)arrow C.
D)line E.

Question 62

Consider the conversion of white tin to gray tin: Sn(white)→ Sn(gray)ΔH° = -2.09 kJ ΔS° = -7.41 J/K
Based on these data,

A)white tin is stable below 9°C and gray tin is stable above 9°C.
B)gray tin is stable below 9°C and white tin is stable above 9°C.
C)white tin is stable below 15°C and gray tin is stable above 15°C.
D)gray tin is stable below 15°C and white tin is stable above 15°C.

Question 63

For the of freezing liquid butane at a given temperature and pressure,

A)ΔH is negative and ΔS is negative.
B)ΔH is negative and ΔS is positive.
C)ΔH is positive and ΔS is negative.
D)ΔH is positive and ΔS is positive.

Question 64

Which of the following is not true?

A)A spontaneous reaction need not occur immediately.
B)A spontaneous reaction must be exothermic and must have an increase in entropy.
C)The reverse of a nonspontaneous reaction is always spontaneous.
D)A spontaneous reaction is one that can proceed on its own.

Question 65

The enthalpy of fusion of naphthalene,C₁₀H₈,is 19.1 kJ/mol at 78.2°C,its melting point.Calculate the entropy of fusion at the melting point.

A)ΔS°_fus = 244 J/(K ∙ mol)
B)ΔS°_fus = 54.4 J/(K ∙ mol)
C)ΔS°_fus = 1.49 J/(K ∙ mol)
D)ΔS°_fus = -1.49 J/(K ∙ mol)

Question 66

For the conversion of water to ice at 25°C and 1 atm,

A)ΔG is negative and ΔH is negative.
B)ΔG is negative and ΔH is positive.
C)ΔG is positive and ΔH is negative.
D)ΔG is positive and ΔH is positive.

Question 67

Imagine a reaction that results in a change in both volume and temperature,as shown in the diagram below.What is the sign of the work being done and the sign of the enthalpy change involved in this reaction?

A)w = + and ΔH = +
B)w = + and ΔH = -
C)w = - and ΔH = +
D)w = - and ΔH = -

Question 68

Methanol can be produced from carbon monoxide and hydrogen with suitable catalysts: CO(g)+ 2 H₂(g)→ CH₃OH(l)at 25°C ΔH° = -128.1 kJ and ΔS° = -332 J/K
Find ΔG° at 25°C.

A)-157.2 kJ
B)-29.1 kJ
C)98.9 kJ
D)157.2 kJ

Question 69

If an endothermic reaction is spontaneous at constant temperature and pressure,

A)ΔG is negative and ΔS may be positive or negative.
B)ΔG is negative and ΔS is positive.
C)ΔG is positive and ΔS is negative.
D)ΔG is positive and ΔS may be positive or negative.

Question 70

The reaction 4 Ag(s)+ O₂(g)→ 2 Ag₂O(s)favors Ag₂O at low temperature,but it favors Ag and O₂ at high temperatures.How can this be explained in terms of ΔH and ΔS?

A)ΔH is negative and ΔS is negative.
B)ΔH is negative and ΔS is positive.
C)ΔH is positive and ΔS is negative.
D)ΔH is positive and ΔS is positive.

Question 71

For the expansion of an ideal gas into a vacuum at constant temperature,ΔH = 0.What can be said about ΔE and ΔS?

A)ΔE is negative and ΔS is positive.
B)ΔE is zero and ΔS is positive.
C)ΔE is negative and ΔS is zero.
D)ΔE is positive and ΔS is negative.

Question 72

Imagine a reaction that results in a change in both volume and temperature,as shown in the diagram below.What is the sign of the work being done,and what is the sign of the enthalpy change involved in this reaction?

A)w = + and ΔH = +
B)w = + and ΔH = -
C)w = - and ΔH = +
D)w = - and ΔH = -

Question 73

Determine the sign of ΔS° for each of the following: I.The mixing of two gases at a given temperature and pressure
II.C(s)+ 2 H₂O(g)→ CO₂(g)+ 2 H₂(g)

A)ΔS° is negative for I and negative for II.
B)ΔS° is negative for I and positive for II.
C)ΔS° is positive for I and negative for II.
D)ΔS° is positive for I and positive for II.

Question 74

Imagine a reaction that results in a change in both volume and temperature,as shown in the diagram below.What is the sign of the work being done,and what is the sign of the enthalpy change involved in this reaction?

A)w = + and ΔH = +
B)w = + and ΔH = -
C)w = - and ΔH = +
D)w = - and ΔH = -

Question 75

If a reaction with a negative value of ΔS is nonspontaneous at constant temperature and pressure,

A)ΔG is negative and ΔH may be positive or negative.
B)ΔG is negative and ΔH is positive.
C)ΔG is positive and ΔH may be positive or negative.
D)ΔG is positive and ΔH is positive.

Question 76

Calculate ΔG° for the reaction below and tell whether it is spontaneous or nonspontaneous under standard conditions at 25°C. 2 S (s)+ 3 O₂ (g)+ 2 H₂O (l)→ 2 H₂SO₄ (l)ΔH° = -1056 kJ/mol
ΔS° = -505 J/mol

A)ΔG° = -1207 kJ and the process is spontaneous.
B)ΔG° = -1207 kJ and the process is nonspontaneous.
C)ΔG° = -906 kJ and the process is spontaneous.
D)ΔG° = -906 kJ and the process is nonspontaneous.

Question 77

Which combination always results in a reaction being spontaneous?

A)ΔH is negative and ΔS is negative.
B)ΔH is negative and ΔS is positive.
C)ΔH is positive and ΔS is negative.
D)ΔH is positive and ΔS is positive.

Question 78

When heated,mercury(II)oxide decomposes into elemental mercury and oxygen: 2 HgO(s)→ 2 Hg(l)+ O₂(g)ΔH° = 181.6 kJ ΔS° = 216.4 J/K
Estimate the temperature at which HgO should begin to decompose if the partial pressure of O₂(g)is constant at 1.00 atm.

A)-34.8°C
B)34.8°C
C)566°C
D)840°C

Question 79

What is the thermodynamic criterion for equilibrium for a reaction at constant temperature and pressure (PV work only)?

A)ΔS = 0
B)ΔG = 0
C)ΔS > 0
D)ΔG < 0

Question 80

Imagine a reaction that results in a change in both volume and temperature,as shown in the diagram below.What is the sign of the work being done and the sign of the enthalpy change involved in this reaction?

A)w = + and ΔH = +
B)w = + and ΔH = -
C)w = - and ΔH = +
D)w = - and ΔH = -