chapter 07crs 10ed

When heat is absorbed by ice (the system) it melts. The quantity q for the system is

1. positive.

2. negative.

When heat is absorbed by ice (the system) it melts. The quantity q for the system is

1. positive.

2. negative.

Catch: Photo of Ice page 498

When potassium chlorate decomposes it produces oxygen gas. From the system’s point of view (which is the convention), w is

1. positive.

2. negative.

3. No work done.

1. positive.

2. negative.

3. No work done.

When potassium chlorate decomposes it produces oxygen gas. From the system’s point of view (which is the convention), w is

Heat is added to the container below while being allowed to expand freely against atmospheric pressure. The temperature and pressure, however, remain constant before and after.

ΔU is,

1. positive.

2. negative.

Heat is added to the container below while being allowed to expand freely against atmospheric pressure. The temperature and pressure, however, remain constant before and after.

ΔU is,

1. positive.

2. negative.

For the following reaction:

2 H2 (g) + O2 (g) g H2O (l) ∆Hº = -572 kJ What is the work associated with this reaction at 25ºC?

1.  7.4 kJ

2.  -7.4 kJ

3.  5.0 kJ

4.  -5.0 kJ

5.  2.5 kJ

For the following reaction:

2 H2 (g) + O2 (g) g H2O (l) ∆Hº = -572 kJ What is the work associated with this reaction at 25ºC?

1.  7.4 kJ

2.  -7.4 kJ

3.  5.0 kJ

4.  -5.0 kJ

5.  2.5 kJ

The volume of the Pacific Ocean is about 300 km3. Without the use of a calculator, estimate the heat that is required to raise the temperature of the Pacific Ocean by 1 oC (assume the density of water is 1 g cm-3 and the specific heat is 4 J g-1 oC-1.

4. ~1018 J

1. ~103 J

2. ~106 J

3. ~1012 J

5. ~1025 J

The volume of the Pacific Ocean is about 300 km3. Without the use of a calculator, estimate the heat that is required to raise the temperature of the Pacific Ocean by 1 oC (assume the density of water is 1 g cm-3 and the specific heat is 4 J g-1 oC-1.

4. ~1018 J

1. ~103 J

2. ~106 J

3. ~1012 J

5. ~1025 J

In 1 minute the sun shines about 40 kJ m-2 of energy on Earth’s surface and about 1018 J is required to raise the temperature of the Pacific by 1 oC. Assuming that all of the sun’s energy is absorbed, how long must the sun shine

1. 4x1021 min

2. 2.5x1011 min

3. 2.5x105 min

4. 2.5x10-5 min

5. 4x10-10 min

Where does the energy come from to heat the ocean?

on the Pacific to raise its temperature by 1 oC? The area of the Pacific ocean is about 100 km2.

In 1 minute the sun shines about 40 kJ m-2 of energy on Earth’s surface and about 1018 J is required to raise the temperature of the Pacific by 1 oC. Assuming that all of the sun’s energy is absorbed, how long must the sun shine

1. 4x1021 min

2. 2.5x1011 min

3. 2.5x105 min

4. 2.5x10-5 min

5. 4x10-10 min

Where does the energy come from to heat the ocean?

on the Pacific to raise its temperature by 1 oC? The area of the Pacific ocean is about 100 km2.

The figure below shows the heating curve for water. It traces the changes in temperature as ice, initially at -20 oC, is gradually heated to produce liquid water at +20 oC. When the ice (the system) melts,

1.  Temperature remains constant, therefore no heat is being added to or removed from the system during the melting of the ice.

2.  Although T is constant, heat is added to convert H2O(s) to H2O(l)

3.  Although T is constant, heat is removed to to convert H2O(s) to H2O(l)

The figure below shows the heating curve for water. It traces the changes in temperature as ice, initially at -20 oC, is gradually heated to produce liquid water at +20 oC. When the ice (the system) melts,

1.  Temperature remains constant, therefore no heat is being added to or removed from the system during the melting of the ice.

2.  Although T is constant, heat is added to convert H2O(s) to H2O(l)

3.  Although T is constant, heat is removed to to convert H2O(s) to H2O(l)

The figure below shows the cooling curve for water. It traces the changes in temperature as water, initially at 20 oC, is gradually cooled to produce ice at -20 oC. When the water (the system) freezes,

1.  the temperature remains constant at 0 oC and the process is endothermic.

2.  the temperature remains constant at 0 oC and the process is exothermic.

3.  the temperature remains constant at 0 oC, thus the process is neither endothermic nor exothermic.

The figure below shows the cooling curve for water. It traces the changes in temperature as water, initially at 20 oC, is gradually cooled to produce ice at -20 oC. When the water (the system) freezes,

1.  the temperature remains constant at 0 oC and the process is endothermic.

2.  the temperature remains constant at 0 oC and the process is exothermic.

3.  the temperature remains constant at 0 oC, thus the process is neither endothermic nor exothermic.

You take two frozen steaks and put them into room temperature water for a few hours to thaw. The heat gained by the steak (system) equals the heat lost by the water (surroundings). The best equation to express this, where subscript ‘s’ refers to steak and the subscript w refers to the water, is,

w w w s s s1. s m T = s m TΔ Δ

w w w s s s2. s m T = s m TΔ − Δ

w w w s s s3. s m T = s m T− Δ Δ

You take two frozen steaks and put them into room temperature water for a few hours to thaw. The heat gained by the steak (system) equals the heat lost by the water (surroundings). The best equation to express this, where subscript ‘s’ refers to steak and the subscript w refers to the water, is,

w w w s s s1. s m T = s m TΔ Δ

w w w s s s2. s m T = s m TΔ − Δ

w w w s s s3. s m T = s m T− Δ Δ

200 g Te (100 oC)

100 g H2O 25 oC

What is the heat capacity of Tellurium? Use 4 J g-1 oC-1 for the heat capacity of water.

2Te H Oq = q−

1. 0.5 J g-1 oC-1

2. 1 J g-1 oC-1

3. 2 J g-1 oC-1

4. 4 J g-1 oC-1

5. 10 J g-1 oC-1

Catch Figure 7-3 here

200 g Te (100 oC)

100 g H2O 25 oC

What is the heat capacity of Tellurium? Use 4 J g-1 oC-1 for the heat capacity of water.

2Te H Oq = q−

1. 0.5 J g-1 oC-1

2. 1 J g-1 oC-1

3. 2 J g-1 oC-1

4. 4 J g-1 oC-1

5. 10 J g-1 oC-1

qP = 250 kJ

T=300 K

V2= 0.110 m3

1x105 Pa

Determine ΔH and ΔU for the reaction and conditions depicted below. Note: 1 Pa = 1 N m-2.

1. 250 kJ, 251 kJ

ΔH ΔU

2. 250 kJ, 249 kJ

3. -250 kJ, -251 kJ

4. -250 kJ, -249 kJ

5. -250 kJ, -250 kJ

V1= 0.120 m3

qP = 250 kJ

T=300 K

V2= 0.110 m3

1x105 Pa

Determine ΔH and ΔU for the reaction and conditions depicted below. Note: 1 Pa = 1 N m-2.

1. 250 kJ, 251 kJ

ΔH ΔU

2. 250 kJ, 249 kJ

3. -250 kJ, -251 kJ

4. -250 kJ, -249 kJ

5. -250 kJ, -250 kJ

V1= 0.120 m3

Ice (the system) melting is

1. an exothermic process.

2. an endothermic process.

3.  neither exothermic nor endothermic since the temperature of the system remains constant (0 oC at 1 atm).

Note: a bit tricky perhaps until chapter 13.

Ice (the system) melting is

1. an exothermic process.

2. an endothermic process.

3.  neither exothermic nor endothermic since the temperature of the system remains constant (0 oC at 1 atm).

Note: a bit tricky perhaps until chapter 13.

The equation for the combustion of butane is,

Which one of the following generates the least heat?

4 10 2 2 213C H (g) + O (g) 4CO (g) + 5H O(g)2

1. Burning one mole of butane in excess oxygen.

2. Reacting one mole of oxygen with excess butane.

3. Producing one mole of carbon dioxide by burning butane.

4. Producing one mole of water by burning butane.

5. Burning 0.25 moles of butane with excess oxygen.

The equation for the combustion of butane is,

Which one of the following generates the least heat?

4 10 2 2 213C H (g) + O (g) 4CO (g) + 5H O(g)2

1. Burning one mole of butane in excess oxygen.

2. Reacting one mole of oxygen with excess butane.

3. Producing one mole of carbon dioxide by burning butane.

4. Producing one mole of water by burning butane.

5. Burning 0.25 moles of butane with excess oxygen.

The chemical reaction representing aerobic respiration is,

6 12 6 2 2 2C H O (s) + 6O (g) 6CO (g) + 6H O(g)→

and is the reverse of photosynthesis. This reaction is exothermic by ~2500 kJ per mole of glucose. A small child exhales about 3 moles of CO2 in a 24 hour period, what is the energy change associated with the photosynthesis reaction required to convert this amount of CO2 back to glucose?

1. 5000 kJ

2. -5000 kJ

3. -2500 kJ

4. 1250 kJ

5. -1250 kJ

The chemical reaction representing aerobic respiration is,

6 12 6 2 2 2C H O (s) + 6O (g) 6CO (g) + 6H O(g)→

and is the reverse of photosynthesis. This reaction is exothermic by ~2500 kJ per mole of glucose. A small child exhales about 3 moles of CO2 in a 24 hour period, what is the energy change associated with the photosynthesis reaction required to convert this amount of CO2 back to glucose?

1. 5000 kJ

2. -5000 kJ

3. -2500 kJ

4. 1250 kJ

5. -1250 kJ

Given the heats of formation of the potential products of the Ostwald process, which reaction is most exothermic?

3 2 2 23 1 31. NH (g) + O (g) N (g) + H O(g)4 2 2

3 2 2 21 32. NH (g) + O (g) N O(g) + H O(g)2 2

3 2 25 33. NH (g) + O (g) NO(g) + H O(g)4 2

3 2 2 27 34. NH (g) + O (g) NO (g) + H O(g)4 2

ΔH / kJ mol-1

N2O 82.1

NO 90.2

NO2 33.2

1. NH3(g) + 34

O2(g) ! 12

N2(g) + 32

H2O(g)

3 2 2 21 32. NH (g) + O (g) N O(g) + H O(g)2 2

3 2 25 33. NH (g) + O (g) NO(g) + H O(g)4 2

3 2 2 27 34. NH (g) + O (g) NO (g) + H O(g)4 2

ΔH / kJ mol-1

N2O 82.1

NO 90.2

NO2 33.2

3 2 2 21. 4NH (g) + 3O (g) 2N (g) + 6H O(g)→

3 2 2 22. 2NH (g) + 2O (g) N O(g) + 3H O(g)→

3 2 23. 4NH (g) + 5O (g) 4NO(g) + 6H O(g)→

3 2 2 24. 4NH (g) + 7O (g) 4NO (g) + 6H O(g)→

ΔH / kJ mol-1

N2O 82.1

NO 90.2

NO2 33.2

NH3 = -46.11kJ/mole

3 2 2 21. 4NH (g) + 3O (g) 2N (g) + 6H O(g)→

3 2 2 22. 2NH (g) + 2O (g) N O(g) + 3H O(g)→

3 2 23. 4NH (g) + 5O (g) 4NO(g) + 6H O(g)→

3 2 2 24. 4NH (g) + 7O (g) 4NO (g) + 6H O(g)→

ΔH / kJ mol-1

N2O 82.1

NO 90.2

NO2 33.2

NH3 = -46.11 kJ/mole

The equations for the complete and incomplete combustion of octane are given below.

8 18 2 2 225C H (l) + O (g) 8CO (g) + 9H O(l)2

8 18 2 217C H (l) + O (g) 8CO(g) + 9H O(l)2

ΔHf / kJ mol-1

CO -111

CO2 -394 Which reaction is more exothermic and by how much?

1. Incomplete by 283 kJ mol-1.

3. Complete by 2264 kJ mol-1.

The equations for the complete and incomplete combustion of octane are given below.

8 18 2 2 225C H (l) + O (g) 8CO (g) + 9H O(l)2

8 18 2 217C H (l) + O (g) 8CO(g) + 9H O(l)2

ΔHf / kJ mol-1

CO -111

CO2 -394 Which reaction is more exothermic and by how much?

Two equations incomplete combustion of butane are given below.

4 10 2 25B. C H (g) + O (g) 8C(graph) + 5H O(l)2

4 10 2 29A. C H (g) + O (g) 4CO(g) + 5H O(l)2

Given that the heat of formation of CO(g) is -111 kJ mol-1, which reaction is more exothermic and by how much?

1. Reaction A by 111 kJ mol-1.

2. Reaction B by 111 kJ mol-1.

5. Not enough information to answer.

ΔHf = -111 kJ mol-1

Two equations incomplete combustion of butane are given below.

4 10 2 25B. C H (g) + O (g) 8C(graph) + 5H O(l)2

4 10 2 29A. C H (g) + O (g) 4CO(g) + 5H O(l)2

Given that the heat of formation of CO(g) is -111 kJ mol-1, which reaction is more exothermic and by how much?

5. Not enough information to answer.

ΔHf = -111 kJ mol-1

Given the bond energies below, estimate the enthalpy change for the addition of Br across the double bond in ethene.

C—C 350 kJ mol-1

C=C 600 kJ mol-1

C—Br 300 kJ mol-1

Br—Br 200 kJ mol-1

1. 150 kJ

2. -150 kJ

3. 220 kJ

4. -220 kJ

5. Not enough data to determine ΔrH

Given the bond energies below, estimate the enthalpy change for the addition of Br across the double bond in ethene.

C—C 350 kJ mol-1

C=C 600 kJ mol-1

C—Br 300 kJ mol-1

Br—Br 200 kJ mol-1

1. 150 kJ

2. -150 kJ

3. 220 kJ

4. -220 kJ

5. Not enough data to determine ΔrH

chapter 07crs 10ed

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