Deck 5: Thermochemistry

Question 1

Given the thermochemical equation:
2 H₂ O₂ ( ) 2 H₂ O ( ) + O₂(g) D H = - 189 kJ What is D H for the formation of 8.00 g of O₂?

A) - 22.2 kJ
B) - 47.2 kJ
C) - 94.5 kJ
D) - 189 kJ
E) none of these

Answer 1

- 47.2 kJ

Question 2

What mass of ethane gas (C₂ H₆ ) must burn in excess oxygen to produce 2.00 10 3 kJ of heat, given the thermochemical equation:
2 C₂ H₆(g) + 7 O₂(g) 4 CO₂ (g) + 6 H₂ O ( ) D H = - 3.12 10 3 kJ

A) 0.641 g
B) 19.3 g
C) 38.6 g
D) heat is not produced by this reaction
E) none of these

Answer 2

38.6 g

Question 3

Given the equation below, what is D H for the reaction that converts 6.00 g of H₂ O ( ) into H₂ O₂ ( ) and H₂ (g)?
2 H₂ O ( ) H₂ O₂ ( ) + H₂ (g) D H = 384 kJ

A) 129 kJ
B) 64.0 kJ
C) 256 kJ
D) 384 kJ
E) none of these

Answer 3

64.0 kJ

Question 4

Consider the following reaction and its corresponding enthalpy:
2 Mg (s) + O₂ (g)→2 MgO (s) D H ° _rxn = - 1204 kJ/mol What amount of heat is exchanged when 5.00 grams of magnesium metal reacts at constant pressure?

A) - 124 kJ
B) - 248 kJ
C) - 3.01×10³ kJ
D) 7.32×10⁴ kJ
E) 1.44×10⁵ kJ

Question 5

Given the equation below, what is D H for burning 10.0 g of CO (g) in excess oxygen?
2 CO (g) + O₂ (g)→2 CO₂ (g) D H = - 566 kJ

A) 101 kJ
B) 202 kJ
C) 50.5 kJ
D) 142 kJ
E) none of these

Question 6

What mass of propane gas (C₃ H₈ ) must burn in excess oxygen to produce 9.00 10 3 kJ of heat, given the thermochemical equation:
C₃ H₈ (g) + 5 O₂(g) 3 CO₂ (g) + 4 H₂ O ( ) D H = - 2.22 10 3 kJ

A) 1.79×10 g
B) 35.8 g
C) 4.05 g
D) heat is not produced by this reaction
E) none of these

Question 7

What mass of nitrogen must burn in excess oxygen to produce 18.0 kJ of heat, given the following thermochemical equation?
N₂ (g) + O₂ (g)→2 NO (g) D H = +1.80×10² kJ

A) 0.100 g
B) 2.80 g
C) 5.60 g
D) heat is not released by this reaction
E) none of these

Question 8

Liquid hydrogen peroxide is an oxidizing agent in many rocket fuel mixtures because it releases oxygen gas on decomposition as shown below. 2 H₂ O₂ ( ) 2 H₂ O ( ) + O₂(g) D H rxn = - 196 kJ How much heat is released when 25.0 grams of H₂ O₂ decomposes?
Molar Mass(H₂ O₂) = 34.01 g/mol

A) - 533 kJ
B) - 288 kJ
C) - 144 kJ
D) - 133 kJ
E) - 72.0 kJ

Question 9

Given the following reaction and its corresponding enthalpy of reaction, how many grams of Fe₂O₃ are produced when 5.62×10³ kJ is released to the surroundings?
Molar Mass (Fe₂O₃) = 159.7 g/mol 4 Fe (s) + 3 O₂ (g)→2 Fe₂O₃ (s) D H _rxn = - 1.65×10³ kJ

A) 46.9 g Fe₂O₃
B) 93.8 g Fe₂O₃
C) 272 g Fe₂O₃
D) 544 g Fe₂O₃
E) 1.09×10³ g Fe₂O₃

Question 10

Energy possessed by a sample of matter because of its position or condition is called

A) chemical energy
B) potential energy
C) kinetic energy
D) heat
E) none of these

Question 11

Which of the following reactions releases heat to the surroundings as it proceeds to completion?
I. C (coal) + H₂O (g) + 130 KJ→CO (g) + H₂ (g)
II. 2 NO₂ (g)→N₂O₄ (exothermic)
III. 2 H₂ (g) + O₂ (g)→2 H₂O (g) D H _rxn = - 572 kJ

A) I only
B) I and III
C) I and II
D) II and III
E) All of these

Question 12

Given the three statements below, which answer is correct?
I. A thermochemical equation must include the physical state of all substances.
II. The coefficients in a thermochemical equation are interpreted as moles.
III. The sign of D H is negative for an endothermic reaction.

A) I and II are true, III is false
B) I and III are true, II is false
C) I, II, and III are all true
D) I, II, and III are all false
E) II and III are true, I is false

Question 13

Given the equation below, what is D H for burning 14.0 g of CO (g) in excess oxygen?
2 CO (g) + O₂ (g)→2 CO₂ (g) D H = - 566 kJ

A) - 566 kJ
B) - 283 kJ
C) - 142 kJ
D) +283 kJ
E) none of these

Question 14

Given the thermochemical equation:
2 SO₂ (g) + O₂ (g)→2 SO₃ (g) D H = - 197 kJ What is D H for the formation of 8.00 g of SO₃?

A) - 9.85 kJ
B) - 19.7 kJ
C) - 39.4 kJ
D) - 197 kJ
E) none of these

Question 15

Given the equation below, what is D H for burning 8.0 g of C₂ H₂ (g) in excess O₂(g)?
2 C₂ H₂ (g) + 5 O₂(g) 4 CO₂ (g) + 2 H₂ O ( ) D H = - 2600 kJ

A) - 200 kJ
B) - 400 kJ
C) - 800 kJ
D) - 1600 kJ
E) none of these

Question 16

Exhibit 5-1 Consider the reaction of Magnesium with oxygen to form magnesium oxide and heat as shown below to answer the following problem(s):
2 Mg (s) + O₂ (g)→2 MgO (s) D H ° _rxn = - 1204 kJ
Refer to Exhibit 5-1. How many grams of MgO are produced during an enthalpy change of - 96.0 kJ?
Molar Mass(MgO) = 40.3 g/mol

A) 1010 g
B) 6.43 g
C) 3.21 g
D) 0.311 g
E) None of these

Question 17

Which of the following reactions absorbs heat from the surroundings in order to proceed to completion?
I. CO (g) + ¹/₂ O₂ (g)→CO₂ (g) D H _rxn = - 283.0 kJ
II. Al₂O₃ (s)→2 Al (s) + ³/₂ O₂ (g) (endothermic)
III. SO₃ (g) + 99.2 kJ→S (s) + ³/₂ O₂ (g)

A) I only
B) I and III
C) I and II
D) II and III
E) All of these

Question 18

Exhibit 5-1 Consider the reaction of Magnesium with oxygen to form magnesium oxide and heat as shown below to answer the following problem(s):
2 Mg (s) + O₂ (g)→2 MgO (s) D H ° _rxn = - 1204 kJ
Refer to Exhibit 5-1. How much heat is released when 2.43 grams of Mg (s) reacts at constant pressure?
Molar Mass(Mg) = 24.3 g/mol

A) - 602 kJ
B) - 240.8 kJ
C) - 120.4 kJ
D) - 60.2 kJ
E) None of these

Question 19

Given the equation below, what is D H for burning 2.00 g of CO (g) in excess oxygen?
2 CO (g) + O₂ (g)→2 CO₂ (g) D H = - 566 kJ

A) - 10.1 kJ
B) - 28.4 kJ
C) - 20.2 kJ
D) - 40.4 kJ
E) none of these

Question 20

Given the three statements below, which answer is correct?
I. An exothermic reaction releases heat to the surroundings.
II. The sign of D H for an exothermic reaction is positive.
III. For an endothermic reaction to be carried out at constant temperature, heat must be supplied from the surroundings.

A) I and II are true, III is false
B) I and III are true, II is false
C) I, II, and III are all true
D) I, II, and III are all false
E) II and III are true, I is false

Question 21

How many joules of heat are necessary to raise the temperature of a 1.42 kg block of copper from 25.0 ° C to 88.5 ° C?
(Specific heat of copper = 0.385 J/g × ° C)

A) 234000 J
B) 34700 J
C) 234 J
D) 34.7 J
E) 0.0347 J

Question 22

When a 40.0 g sample of a metal at 25.00 ° C is added tO₆5.0 g of water at 100.00 ° C, the final temperature of both the water and metal is 93.27 ° C. The specific heat of water is 4.184 J/g × K. What is the specific heat of the metal?

A) 0.670 J/g × K
B) 1.49 J/g × K
C) 0.254 J/g × K
D) 1.03 J/g × K
E) none of these

Question 23

What is the specific heat of an unknown substance if 25.0 grams of the substance absorbs 77.0 calories of heat and the temperature increases by 5.5 ° C?

A) 0.51 cal/g × ° C
B) 0.513 cal/g × ° C
C) 0.56 cal/g × ° C
D) 0.616 cal/g × ° C
E) 0.62 cal/g × ° C

Question 24

How many calories of heat energy are required to raise the temperature of 25.0 g of silver from 25 ° C tO₅ 0 ° C?
Specific Heat(Ag) = 0.057 cal/g × ° C

A) 0.057 calories
B) 18 calories
C) 36 calories
D) 48 calories
E) 48.0 calories

Question 25

A chemical reaction releases enough heat to raise the temperature of 77.2 g of water from 24.30 ° C tO₄5.60 ° C. Given that the specific heat of water is 4.184 J/g × K, what is the heat evolved?

A) 6.02 kJ
B) 4.585 kJ
C) 9.15 kJ
D) 6.88 kJ
E) none of these

Question 26

How much heat must be added to a 4.33 g piece of aluminum to raise its temperature from 22.00 ° C to 27.00 ° C?
Specific Heat(Al) = 0.900 J/g × K

A) 19.5 J
B) 22.8 J
C) 6.88 J
D) 15.2 J
E) none of these

Question 27

When a 60.0 g sample of a metal at 100.0 ° C is added tO₄5.0 g of water at 22.00 ° C, the final temperature of both the water and metal is 32.81 ° C. The specific heat of water is 4.184 J/g × K. What is the specific heat of the metal?

A) 33.9 J/g × K
B) 0.339 J/g × K
C) 0.505 J/g × K
D) 0.199 J/g × K
E) none of these

Question 28

The reaction of 8.00 g of SO₂ (g) burns in excess oxygen. 9.85 kJ of heat are released. What is D H for the following thermochemical equation?
2 SO₂ (g) + O₂ (g)→2 SO₃ (g)

A) - 1.58×10² kJ
B) - 78.8 kJ
C) - 39.4 kJ
D) +78.8 kJ
E) none of these

Question 29

When a 50.0 g sample of a metal at 100.0 ° C is added tO₆0.0 g of water at 25.10 ° C, the final temperature of both the water and metal is 32.81 ° C. The specific heat of water is 4.184 J/g × K. What is the specific heat of the metal?

A) 0.576 J/g × K
B) 1.66 J/g × K
C) 45.0 J/g × K
D) 0.900 J/g × K
E) none of these

Question 30

How many calories of heat are required to heat 52.7 g of Aluminum from 100 ° C to 285 ° C?
Specific Heat(Al) = 0.22 cal/g × ° C

A) 1.3 cal
B) 16 cal
C) 2.1×10³ cal
D) 3.3×10³ cal
E) 4.4×10⁴ cal

Question 31

When 5.00 g of butane, C₄H₁₀ (g), burns in oxygen, 247 kJ of heat are released. What is D H for the following thermochemical equation?
2 C₄H₁₀ (g) + 13 O₂(g) 8 CO₂ (g) + 10 H₂ O ( )

A) +2.87×10³ kJ
B) +5.74×10³ kJ
C) - 5.74×10³ kJ
D) - 2.87×10³ kJ
E) none of these

Question 32

Which statement below is true?

A) Some substances have a negative specific heat.
B) In endothermic reactions, heat is given off to the surroundings.
C) Specific heat is the same for all liquids but metals each have a different specific heat.
D) In exothermic reactions, the sign of D H is always negative.
E) All four of these are false.

Question 33

How much heat must be removed from a 10.0 g sample of graphite (specific heat = 0.720 J/g × K) to decrease its temperature from 55.00 ° C tO₄4.00 ° C?

A) 0.720 J
B) 7.20 J
C) 7.92 J
D) 79.2 J
E) none of these

Question 34

When 10.0 g of ethane, C₂ H₆(g), burns in oxygen, 519 kJ of heat are released. What is D H for the following thermochemical equation?
2 C₂ H₆(g) + 7 O₂(g) 4 CO₂ (g) + 6 H₂ O ( )

A) +3.12×10³ kJ
B) +1.56×10³ kJ
C) - 3.12×10³ kJ
D) - 1.56×10³ kJ
E) none of these

Question 35

How much heat must be added to a 2.22 g piece of gold (specific heat = 0.129 J/g × K) to raise its temperature from 25.00 ° C to 34.00 ° C?

A) 2.44 J
B) 2.86 J
C) 2.58 J
D) 15.2 J
E) none of these

Question 36

A chemical reaction releases enough heat to raise the temperature of 35.2 g of water from 25.60 ° C to 34.80 ° C. Given that the specific heat of water is 4.184 J/g × K, what is the heat evolved?

A) 6.22 kJ
B) 2.55 kJ
C) 9.15 kJ
D) 1.35 kJ
E) none of these

Question 37

The heat exchange of a certain exothermic reaction is measured in a solution calorimeter. The sign convention for the heat exchanged in this process would be a ____ value for the heat released in the reaction and a ____ value for the heat absorbed by the calorimeter.

A) negative ( - ), positive (+)
B) positive (+), negative ( - )
C) negative ( - ), negative ( - )
D) positive (+), positive (+)

Question 38

How much heat is required to raise the temperature of 25.0 grams of water from 32.0 ° C to 87.0 ° C?
Specific Heat (H₂O) = 4.184 J/g × ° C

A) 9.20 J
B) 329 J
C) 3.35×10³ J
D) 5.75×10³ J
E) 1.05×10⁴ J

Question 39

A reaction of 3.44 g of H₂ (g) and 20.5 g of C (s) yields C₃H₆ (g), and the enthalphy change is - 11.6 kJ. What is D H for the following reaction?
3 H₂ (g) + 3 C (s)→C₃H₆ (g)

A) - 20.4 kJ
B) - 11.6 kJ
C) - 31.7 kJ
D) - 61.2 kJ
E) none of these

Question 40

When a 83.0 g sample of a metal at 100.0 ° C is added tO₄5.0 g of water at 23.25 ° C, the final temperature of both the water and metal is 27.68 ° C. The specific heat of water is 4.184 J/g × K. What is the specific heat of the metal?

A) 10.0 J/g × K
B) 11.5 J/g × K
C) 0.100 J/g × K
D) 0.139 J/g × K
E) none of these

Question 41

What is the final temperature upon mixing 75.0 grams of water held at 45.0 ° C witH₂ 5.0 grams of water held at 90.0 ° C?

A) 11.3 ° C
B) 28.1 ° C
C) 56.3 ° C
D) 67.5 ° C
E) 78.8 ° C

Question 42

The specific heat of water is 4.184 J/g × ° C. What is the heat capacity of 0.185 kg of liquid water?

A) 774 J/ ° C
B) 44.2 J/ ° C
C) 22.6 J/ ° C
D) 4.184 J/ ° C
E) 0.7774 J/ ° C

Question 43

Given the following two equations and their respective enthalpies:
S (s) + O₂ (g)→SO₂ (g) D H _rxn = - 296.8 kJ/mol S (s) + ³/₂ O₂ (g)→SO₃ (g) D H _rxn = - 395.6 kJ/mol What is the enthalpy change D H _rxn for the following reaction?
2 SO₃ (g)→2 SO₂ (g) + O₂ (g) D H _rxn = ???

A) - 692.4 kJ/mol
B) 197.6 kJ/mol
C) 98.8 kJ/mol
D) - 1384.8 kJ/mol
E) None of these

Question 44

Given the following information:
¹/₂ N₂ (g) + ¹/₂ O₂ (g)→NO (g) D H = 90.3 kJ NO (g) + ¹/₂ Cl₂ (g)→NOCl (g) D H = - 38.6 kJ What is the enthalpy of reaction D H _rxn for the reaction that follows?
2 NOCl (g)→N₂ (g) + O₂ (g) + Cl₂ (g) D H _{net rxn} = ??

A) D H = - 257.8 kJ
B) D H = - 103.4 kJ
C) D H = - 25.9 kJ
D) D H = - 13.1 kJ
E) D H = 51.7 kJ

Question 45

Given the equations listed below and their corresponding enthalpies:
N₂O₄ (g)→2 NO₂ (g) D H = 58 kJ 2 NO (g) + O₂ (g)→2 NO₂ (g) D H = - 112 kJ What is D H for the following reaction?
2 NO (g) + O₂ (g)→N₂O₄ (g)

A) - 170 kJ
B) - 54 kJ
C) - 112 kJ
D) - 2 kJ
E) none of these

Question 46

Which of the following substances would have a Standard Molar Enthalpy of Formation equal to zero, D H ° _f = 0?

A) H₂ O ( )
B) CO₂ (g)
C) N₂ (g)
D) CH₄ (g)
E) O₂( )

Question 47

75.0 joules of heat is supplied to ethanol that has a mass of 125 g. What temperature change does this sample of ethanol undergo?
Specific Heat(ethanol) = 2.427 J/g × ° C

A) 0.247 ° C
B) 1.46 ° C
C) 4.05 ° C
D) 3.86×10³ ° C
E) 2.28×10⁴ ° C

Question 48

Given the following data:
Fe₂O₃ (s) + 3 CO (g)→2 Fe (s) + 3 CO₂ (g) D H = - 25 kJ/mol 2 CO (g) + O₂ (g)→2 CO₂ (g) D H = - 566 kJ/mol What is the molar enthalpy of reaction D H _rxn for the following reaction?
4 Fe (s) + 3 O₂ (g)→2 Fe₂O₃ (s) D H _rxn = ??

A) - 541 kJ/mol
B) - 591 kJ/mol
C) - 1057 kJ/mol
D) - 1648 kJ/mol
E) - 1748 kJ/mol

Question 49

A 350 gram aluminum part at an initial temperature of 25.0 ° C absorbs 6200 J of heat. What is the final temperature of the aluminum part?
C(Al) = 0.900 J/g × ° C

A) 5.3 ° C
B) 15.9 ° C
C) 19.7 ° C
D) 40.9 ° C
E) 44.7 ° C

Question 50

Which of the following substances would be expected to have an enthalpy of formation value D H f equal to zero?
(Pay careful attention to the phase indicators.)
I. O₂(g)
II. N₂( )
III. H₂ O ( )

A) I only
B) I and II
C) I and III
D) II and III
E) All of these

Question 51

50.0 calories of heat is supplied to a piece of gold of unknown mass. The temperature of the gold ingot raises 15.4 ° C. What is the mass of the gold ingot in grams?
Specific Heat(Au) = 0.0310 cal/g × ° C

A) 9.55×10 ^{- 3} g
B) 0.101 g
C) 9.94 g
D) 23.9 g
E) 105 g

Question 52

Given the thermochemical equations and their corresponding enthalpies:
CH₄ (g) + 2 O₂(g) CO₂ (g) + 2 H₂ O ( ) D H = - 890 kJ C₂ H₄ (g) + 3 O₂(g) 2 CO₂ (g) + 2 H₂ O ( ) D H = - 1410 kJ What is the D H for the following reaction?
2 CH₄ (g) + O₂(g) C₂ H₄ (g) + 2 H₂ O ( )

A) 3190 kJ
B) - 2300 kJ
C) - 520 kJ
D) - 370 kJ
E) none of these

Question 53

Which of the following substances is expected to have a standard molar enthalpy of formation D H ° _f equal to zero?

A) NaCl (s)
B) H₂ (g)
C) HCl (aq)
D) N₂( )
E) CO₂ (s)

Question 54

When a 2.00 g sample of ammonium nitrate (NH₄NO₃) dissolves in 48.0 g of water the temperature changes from 26.57 ° C to 23.50 ° C. Assuming the specific heat of the solution is 4.184 J/g × K, what is the enthalpy change for dissolving 2.00 g of ammonium nitrate in water?

A) +616 J
B) +642 J
C) - 642 J
D) - 616 J
E) none of these

Question 55

Given the following two equations and their corresponding enthalpies:
CO (g) + ¹/₂ O₂ (g)→CO₂ (g) D H ₁ = - 283.0 kJ N₂ (g) + O₂ (g)→2 NO (g) D H ₂ = 180.6 kJ What is the enthalpy of reaction D H _rxn for the reaction that follows?
CO (g) + NO (g)→CO₂ (g) + ¹/₂ N₂ (g) D H _{net rxn} = ??

A) D H _rxn = - 746.6 kJ
B) D H _rxn = - 385.4 kJ
C) D H _rxn = - 373.3 kJ
D) D H _rxn = - 192.7 kJ
E) D H _rxn = - 102.4 kJ

Question 56

Given the following thermochemical equations and their corresponding enthalpies:
2 C₂ H₂ (g) + 5 O₂(g) 4 CO₂ (g) + 2 H₂ O ( ) D H = - 2601 kJ C₈ H₈ ( ) + 10 O₂(g) 8 CO₂ (g) + 4 H₂ O ( ) D H = - 4393 kJ What is the enthalpy change for the following reaction?
4 C₂ H₂ (g) C₈ H₈ ( ) D H = ?

A) - 1792 kJ
B) - 809 kJ
C) - 6994 kJ
D) - 9595 kJ
E) none of these

Question 57

Which of the following substances would have a standard enthalpy of formation D H f equal to 0 kJ?
(Pay careful attention to the phase indicators.)
I. H₂ O ( )
II. Fe (g)
III. C (s; graphite)

A) I only
B) II only
C) III only
D) I and III
E) II and III

Question 58

Which unit from those listed below would be the best choice as a unit for the heat capacity of a substance?

A) J
B) J/mol
C) J/g
D) J/ ° C
E) J/g × ° C

Question 59

Given the equations shown below and their corresponding enthalpies:
H₂ O₂ ( ) H₂ O ( ) + 1 / 2 O₂(g) D H = - 98 kJ H₂ (g) + 1 / 2 O₂(g) H₂ O ( ) D H = - 285 kJ What is D H for the following reaction?
H₂ O₂ ( ) H₂ (g) + O₂(g)

A) - 383 kJ
B) - 187 kJ
C) 383 kJ
D) 187 kJ
E) none of these

Question 60

In a calorimetry experiment, 0.500 g of copper dissolved in water that contains bromine, 1382 joules of heat were released to the surroundings. What is D H for the following thermochemical equation?
Cu (s) + Br₂ (aq)→CuBr₂ (aq) D H = ?

A) - 2.76 kJ
B) +2.76 kJ
C) - 176 kJ
D) - 351 kJ
E) none of these

Question 61

Given the data below, what is D H for the following reaction?
2 CH₄ (g) + 3 O₂(g) 2 CO (g) + 4 H₂ O ( ) D H f CH₄ (g) = - 75 kJ/mol D H f CO (g) = - 110 kJ/mol D H f H₂ O ( ) = - 286 kJ/mol

A) - 1214 kJ
B) - 1514 kJ
C) - 321 kJ
D) - 842 kJ
E) none of these

Question 62

Given the data below, what is D H for the following reaction?
2 H₂ S (g) + 3 O₂(g) 2 H₂ O ( ) + 2 SO₂ (g) D H f H₂ S (g) = - 21 kJ/mol D H f H₂ O ( ) = - 286 kJ/mol D H f SO₂ (g) = - 297 kJ/mol

A) - 562 kJ
B) 832 kJ
C) - 1124 kJ
D) - 1420 kJ
E) none of these

Question 63

What is the enthalpy of reaction D H rxn for the following reaction?
SiO₂ (s) + 4 HF (g) SiF₄ (g) + 2 H₂ O ( ) D H rxn = ??
D H f (SiO₂ ) = - 910.9 kJ/mol D H f (HF) = - 273.0 kJ/mol D H f (SiF₄ ) = - 1614.9 kJ/mol D H f (H₂ O) = - 285.8 kJ/mol

A) - 183.6 kJ/mol
B) - 716.8 kJ/mol
C) - 1002.6 kJ/mol
D) - 3084.6 kJ/mol
E) - 4189.4 kJ/mol

Question 64

Given the standard heats of formation listed below, what is D H for the following reaction?
C₆ H₁₂ O₆ (s) + 6 O₂(g) 6 CO₂ (g) + 6 H₂ O ( ) D H f C₆ H₁₂ O₆ (s) = - 1268 kJ/mol D H f CO₂ (g) = - 394 kJ/mol D H f H₂ O ( ) = - 286 kJ/mol

A) - 5332 kJ
B) +588 kJ
C) - 2812 kJ
D) None of these answers are correct (although the problem can be worked with the data given).
E) Not enough information is given to work the problem.

Question 65

Which of the equations below corresponds to the standard molar enthalpy of formation for AgNO₃, D H _f(AgNO₃)?

A) Ag (s) + ¹/₂ N₂ (g) + ³/₂ O₂ (g)→ AgNO₃ (s)
B) Ag⁺¹ (aq) + NO₃ ^{- 1} (aq)→ AgNO₃ (s)
C) Ag (s) + N (g) + O₃ (g)→ AgNO₃ (s)
D) 2 Ag (s) + N₂ (g) + 3 O₂ (g)→ 2 AgNO₃ (s)

Question 66

For which of the equations shown below does the standard enthalpy of reaction equal the standard molar enthalpy of reaction of the product?
I. 1 / 2 N₂(g) + 3 / 2 H₂ (g) NH₃(g)
II. H₂ (g) + Br₂( ) 2 HBr (g)
III. HCl (g) + NH₃(g) NH ₄Cl (s)

A) I only
B) II only
C) III only
D) I and II
E) I and III

Question 67

Which of the following defines the heat of formation of Cr₂O₃ (s)?

A) 2 Cr (s) + 3 O (g)→ Cr₂O₃ (s)
B) 2 Cr (s) + ³/₂ O₂ (g)→ Cr₂O₃ (s)
C) 4 Cr (s) + 3 O₂ (g)→ 2 Cr₂O₃ (s)
D) Cr₂ (s) + ³/₂ O₂ (g)→ Cr₂O₃ (s)
E) none of these

Question 68

Given the following Thermodynamic data:
D H f (Fe₂ O₃ ; s) = - 822 kJ/mol D H f (FeCl 3 ; s) = - 400 kJ/mol D H f (H₂ O; g) = - 242 kJ/mol D H f (H₂ O; ) = - 286 kJ/mol D H f (HCl; g) = - 92 kJ/mol D H f (HCl; aq) = - 167 kJ/mol What is the Standard Molar Enthalpy of Reaction D H rxn for the following reaction?
Fe₂ O₃(s) + 6 HCl (g) 2 FeCl 3 (s) + 3 H₂ O (g) D H rxn = ??

A) - 1256 kJ/mol
B) - 284 kJ/mol
C) - 152 kJ/mol
D) 272 kJ/mol
E) 298 kJ/mol

Question 69

Given the data below, what is D H for the following reaction?
CH₄ (g) + 2 O₂(g) CO₂ (g) + 2 H₂ O ( ) D H f CH₄ (g) = - 75 kJ/mol D H f CO₂ (g) = - 394 kJ/mol D H f H₂ O ( ) = - 286 kJ/mol

A) - 891 kJ
B) - 605 kJ
C) +605 kJ
D) +891 kJ
E) none of these

Question 70

For which of the equations shown below does the standard enthalpy of reaction equal the standard molar enthalpy of reaction of the product?
I. N₂(g) + O₂(g) 2 NO (g)
II. C (s; graphite) + O₂(g) CO₂ (g)
III. H₂ O ( ) + CO₂ (g) H₂ CO₃( )

A) I only
B) II only
C) III only
D) II and III
E) All of these

Question 71

What is the enthalpy of reaction D H ° _rxn for the following reaction?
2 C₂H₆ (g) + 7 O₂ (g)→4 CO₂ (g) + 6 H₂O (g) D H ° _rxn = ??
D H ° _f(C₂H₆) = - 84.7 kJ/mol D H ° _f(CO₂) = - 393.5 kJ/mol D H ° _f(H₂O) = - 241.8 kJ/mol

A) - 3194.2 kJ/mol
B) - 2855.4 kJ/mol
C) - 1674.9 kJ/mol
D) - 1646.4 kJ/mol
E) - 550.6 kJ/mol

Question 72

Which of the following defines the heat of formation of Fe₂O₃ (s)?

A) 2 Fe (g) + 3 O (g)→ Fe₂O₃ (s)
B) 2 Fe (s) + ³/₂ O₂ (g)→ Fe₂O₃ (s)
C) 4 Fe (s) + 2 O₃ (g)→ 2 Fe₂O₃ (s)
D) 2 Fe (g) + 3 O (g)→ Fe₂O₃ (g)
E) none of these

Question 73

What is the standard molar enthalpy change D H rxn for the following reactions using the standard molar enthalpies of formations provided?
SiCl 4 ( ) + 2 H₂ O ( ) SiO₂ (s) + 4 HCl (g) D H rxn = ???
D H f (SiCl 4 ) = - 640.1 kJ/mol D H f (SiO₂ ) = - 910.9 kJ/mol D H f (H₂ O) = - 285.8 kJ/mol D H f (HCl) = - 92.3 kJ/mol

A) - 2491.8 kJ/mol
B) - 1929.1 kJ/mol
C) - 77.3 kJ/mol
D) - 68.4 kJ/mol
E) None of these

Question 74

Given the following experimental data:
D H rxn Ca (s) + 2 H₂ O ( ) Ca(OH) 2 (s) + H₂ (g) - 415.1 kJ 1 / 2 H₂ (g) + 1 / 2 Cl₂ 2 HCl (g) - 92.31 kJ CaCl₂ (s) + 2 H₂ O ( ) Ca(OH) 2 (s) + 2 HCl (g) 195.3 kJ What is the standard heat of formation ( D H f ) for CaCl₂ (s)?

A) - 795.0 kJ/mol
B) - 311.3 kJ/mol
C) - 116.8 kJ/mol
D) +127.5 kJ/mol
E) +702.6 kJ/mol

Question 75

Given the data below, what is D H for the following reaction?
C₂ H₅ OH ( ) + 3 O₂(g) 2 CO₂ (g) + 3 H₂ O ( ) D H f C₂ H₅ OH ( ) = - 278 kJ/mol D H f CO₂ (g) = - 394 kJ/mol D H f H₂ O ( ) = - 286 kJ/mol

A) - 1368 kJ
B) - 401 kJ
C) +1368 kJ
D) +402 kJ
E) none of these

Question 76

Given the data below, what is D H for the following reaction?
4 NO (g) + 6 H₂ O ( ) 4 NH₃(g) + 5 O₂(g) D H f H₂ O ( ) = - 286 kJ/mol D H f NH₃(g) = - 46 kJ/mol D H f NO (g) = 90 kJ/mol

A) +1172 kJ
B) +149 KJ
C) - 149 kJ
D) - 1172 kJ
E) none of these

Question 77

Given the data below, what is D H ° for the following reaction?
CH₄ (g) + 3 Cl₂ (g)→CHCl₃ (g) + 3 HCl (g) D H ° _f [CH₄ (g)] = - 75 kJ/mol D H ° _f [CHCl₃ (g)] = - 103 kJ/mol D H ° _f [HCl (g)] = - 92 kJ/mol

A) - 304 kJ
B) - 120 kJ
C) +304 kJ
D) +120 kJ
E) none of these

Question 78

Which of the equations listed below corresponds to the standard molar enthalpy of formation D H ° _f for NH₄NO₃?

A) NH₄⁺ (aq) + NO₃ ^- (aq)→ NH₄NO₃ (s)
B) NH₃ (g) + HNO₃ (g)→ NH₄NO₃ (s)
C) N₂ (g) + 2 H₂ (g) + ³/₂ O₂ (g)→ NH₄NO₃ (s)
D) 2 N₂ (g) + 4 H₂ (g) + 3 O₂ (g)→ 2 NH₄NO₃ (s)
E) 2 N (g) + 4 H (g) + 3 O (g)→ NH₄NO₃ (s)