Deck 8: Thermochemistry: Chemical Energy

Question 1

Which depends only on the initial and final state?

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

Answer 1

q + w

Question 2

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

Answer 2

E,the internal energy

Question 3

Which of the following is not a type of energy or energy transfer?

A)chemical energy
B)heat
C)temperature
D)work

Answer 3

temperature

Question 4

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

Question 5

The nutritional calorie (abbreviated Cal)is equal to

A)1 mcal.
B)4)184 J.
C)4)184 cal.
D)1 kcal.

Question 6

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 7

The first law of thermodynamics

A)defines chemical energy.
B)defines entropy.
C)is a statement of conservation of energy.
D)provides a criterion for the spontaneity of a reaction.

Question 8

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 9

Calculate the work energy,w,gained or lost by the system when a gas expands from 15 L to 35 L against a constant external pressure of 1.5 atm.[1 L ∙ atm = 101 J]

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

Question 10

A slice of cheese pizza has a caloric content of 150 Cal.If this energy could be used to power a 2500 Watt microwave oven,how many minutes could the microwave oven be operated?

A)1)0 min
B)4)2 min
C)11 min
D)15 min

Question 11

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.

Question 12

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 13

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 14

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 decrease and work will be done on the system.

Question 15

Which of the following is not a state function?

A)altitude
B)heat
C)internal energy
D)volume

Question 16

At 298 K the average kinetic energy is the same for H₂,He,and N₂.The gas with the highest average velocity is

A)H₂.
B)He.
C)N₂.
D)All have the same average velocity.

Question 17

For a system at constant pressure,12,400 calories of heat are released.This quantity of heat is equivalent to

A)1)92 × 10^-5 J.
B)2)96 × 10³ J.
C)1)24 × 10⁴ J.
D)5)19 × 10⁴ J.

Question 18

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 19

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 20

For a particular process that is carried out at constant pressure,q = 125 kJ and w = -15 kJ.Therefore,

A)ΔE = 110 kJ and ΔH = 125 kJ.
B)ΔE = 125 kJ and ΔH = 110 kJ.
C)ΔE = 125 kJ and ΔH = 140 kJ.
D)ΔE = 140 kJ and ΔH = 125 kJ.

Question 21

At constant pressure,the combustion of 5.00 g of C₂H₆(g)releases 259 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

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 23

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 24

At constant pressure for which of the reactions shown below should ΔH° be greater than ΔE° ?
I.2 SO₂(g)+ O₂(g)→ 2 SO₃(g)
II.C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(l)
III.H₂(g)+ Cl₂(g)→ 2 HCl(g)
IV.N₂O₄(g)→ 2 NO₂(g)

A)I)
B)III.
C)IV.
D)II.and IV.

Question 25

The heat of vaporization of water at 100°C is 40.66 kJ/mol.Calculate the quantity of heat that is absorbed/released when 5.00 g of steam condenses to liquid water at 100°C.

A)11.3 kJ of heat are absorbed.
B)11.3 kJ of heat are released.
C)147 kJ of heat are absorbed.
D)147 kJ of heat are released.

Question 26

At a constant pressure of 1.50 atm what is the enthalpy change ΔH for a reaction where the internal energy change ΔE is 58.0 kJ and the volume increase is 12.6 L? (1 L·atm = 101.325 J. )

A)39.1 kJ
B)56.1 kJ
C)59.9 kJ
D)76.9 kJ

Question 27

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 28

Under thermodynamic standard state conditions the element oxygen occurs as

A)O(g)
B)O₂(g)
C)O₂(l)
D)O₃(g)

Question 29

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 30

How much heat is absorbed/released when 20.00 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)342.9 kJ of heat are absorbed.
B)342.9 kJ of heat are released.
C)1372 kJ of heat are absorbed.
D)1372 kJ of heat are released.

Question 31

Calculate the total quantity of heat required to convert 25.0 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 3.27 kJ/mol,and its heat of vaporization is 29.82 kJ/mol.

A)1)11 kJ
B)1)64 kJ
C)5)96 kJ
D)6)49 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 1.50 mol of gallium at 1 atm pressure?

A)6 kJ
B)9 kJ
C)268 kJ
D)271 kJ

Question 33

When 2.000 moles of H₂(g)reacts with 1.000 mol of O₂(g)to form 2.000 mol of H₂O(l)at 25°C and a constant pressure of 1.00 atm.If 136.6 kJ of heat are released during this reaction,and PΔV is equal to -7.400 kJ,then

A)ΔH° = +136.6 kJ and ΔE° = +144.0 kJ.
B)ΔH° = +136.6 kJ and ΔE° = +129.2 kJ.
C)ΔH° = -136.6 kJ and ΔE° = -129.2 kJ.
D)ΔH° = -136.6 kJ and ΔE° = -144.0 kJ.

Question 34

When 0.250 mol of CH₄(g)reacts with excess Cl₂(g)at constant pressure according to the chemical equation shown below,177 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)-1420 kJ
B)-708 kJ
C)+708 kJ
D)+1420 kJ

Question 35

When 1.00 mol of benzene is vaporized at a constant pressure of 1.00 atm and at its normal boiling point of 80.1°C,33.9 kJ are absorbed and PΔV for the vaporization process is equal to 2.90 kJ,then

A)ΔE = 31.0 kJ and ΔH = 33.9 kJ.
B)ΔE = 36.8 kJ and ΔH = 33.9 kJ.
C)ΔE = 33.9 kJ and ΔH = 31.0 kJ.
D)ΔE = 33.9 kJ and ΔH = 36.8 kJ.

Question 36

How much heat is transferred per mole of NH₃(g)formed in the reaction shown below?
N₂(g)+ 3 H₂(g)→ 2 NH₃(g)ΔH° = - 92.2 kJ

A)92.2 kJ
B)46.1 kJ
C)30.7 kJ
D)15.4 kJ

Question 37

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 38

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 39

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 40

How much heat is absorbed when 30.00 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)119.9 kJ
B)239.9 kJ
C)599.2 kJ
D)1439 kJ

Question 41

Given: 4 NO₂(g)+ O₂(g)→ 2 N₂O₅(g)ΔH° = -110.2 kJ
Find ΔH° for N₂O₅(g)→ 2 NO₂(g)+ 1/2 O₂(g).

A)-220.4 kJ
B)-55.1 kJ
C)55.1 kJ
D)220.4 kJ

Question 42

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 43

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 44

It takes 11.2 kJ of energy to raise the temperature of 145 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 45

Which is expected to have the most negative standard enthalpy of formation?

A)H₂(g)
B)O₂(g)
C)H₂O(g)
D)H₂O(l)

Question 46

Sodium metal reacts with water to produce hydrogen gas and sodium hydroxide according to the chemical equation shown below.When 0.0300 mol of Na is added to 100.00 g of water,the temperature of the resulting solution rises from 25.00°C to 37.90°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 47

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 25.00°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)24.45°C
B)25.55°C
C)26.10°C
D)26.65°C

Question 48

The values of ΔH°_f for the three states of benzene are approximately -22 kcal/mol,-11 kcal/mol,and 20 kcal/mol.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 49

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 50

Find ΔH for BaCO₃ (s)→ BaO (s)+ CO₂ (g)
Given 2 Ba (s)+ O₂ (g)→ 2 BaO (s)ΔH = -1107.0 kJ
Ba (s)+ CO₂ (g)+ 1/2 O₂ (g)→ BaCO₃ (g)ΔH = -822.5 kJ

A)-1929.5 kJ
B)-1376.0 kJ
C)-284.5 kJ
D)269.0 kJ

Question 51

Find ΔH for C₃H₈ (g)+ 6 H₂O (g)→ 3 CO₂ (g)+ 10 H₂
Given C₃H₈ (g)+ 3 H₂O (g)→ 3 CO (g)+ 7 H₂ (g)ΔH = 499 kJ
CO (g)+ H₂O (g)→ CO₂ (g)+ H₂ (g)ΔH = -41 kJ

A)376 kJ
B)458 kJ
C)540 kJ
D)622 kJ

Question 52

When 0.455 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 8.63°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)-7070 kJ/mol
D)-8120 kJ/mol

Question 53

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),and 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 54

Water has an unusually high

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

Question 55

The specific heat of copper is 0.385 J/(g ∙°C).If 34.2 g of copper,initially at 25°C,absorbs 4.689 kJ,what will be the final temperature of the copper?

A)25.4°C
B)27.8°C
C)356°C
D)381°C

Question 56

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 57

10.0 g of a metal,initially at 25°C,are placed into 10.0 g of water,initially at 100°C.Which metal will have the highest final temperature? Shown after each metal is its specific heat in J/(g∙°C).

A)aluminum (0.902)
B)copper (0.385)
C)Gold (0.129)
D)iron (0.450)

Question 58

Which is expected to have the lowest specific heat capacity at 25°C?

A)air
B)copper
C)polyethylene
D)water

Question 59

When 1.50 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 33.10°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 60

For which should the standard heat of formation ΔH°_f,be zero at 25°C?

A)O(g)
B)O₂(g)
C)O₃(g)
D)all the above

Question 61

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 62

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 63

Which is expected to have the largest carbon-oxygen bond dissociation energy?

A)CO
B)CO₂
C)HCO₂H
D)CO₃^2-

Question 64

For the of freezing liquid ethanol 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 65

For which reaction is H expected to be most positive?

A)N₂(g)→ 2 N(g)
B)O₂(g)→ 2 O(g)
C)2 N(g)→ N₂(g)
D)2 O(g)→ O₂(g)

Question 66

Acetylene torches utilize the following reaction:
2 C₂H₂(g)+ 5 O₂(g)→ 4 CO₂(g)+ 2 H₂O(g)
Use the given standard enthalpies of formation to calculate ΔH° for this reaction.

A)2512.4 kJ
B)1256.2 kJ
C)-1256.2 kJ
D)-2512.4 kJ

Question 67

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 68

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 69

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

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

Question 70

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 71

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 72

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 73

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 74

Which thermodynamic function is most related to disorder and probability?

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

Question 75

For the reaction,NH₃(g)→ N(g)+ 3 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 76

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 77

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 78

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 79

At a given temperature and pressure,which of the following would be expected to have the greatest molar entropy?

A)Br₂(s)
B)Br₂(l)
C)Br₂(g)
D)All of these would be expected to have the same molar entropy.

Question 80

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