Question 1

Which of the following best describes the Law of Conservation of Energy?

Accepted Answer

Energy can be neither created nor destroyed; it can only be transformed from one form to another.

Question 2

A 300 g piece of gold is heated from 20°C to 45°C and absorbs 322 J of heat. Assuming the volume of the gold remains constant, what is the change in internal energy ($$\Delta U) of $$the gold?

Accepted Answer

$$\Delta U = 322 J$$

Question 3

Which of the following scenarios is an example of energy transfer as work?

Accepted Answer

A metal cylinder is rolled up a ramp.

Question 4

Given the reaction: $$4	ext{NH}_3(g) + 5	ext{O}_2(g) ightarrow 4	ext{NO}(g) + 6	ext{H}_2	ext{O}(g)$$ with $$\Delta H_{rxn} = -902.0\ 	ext{kJ/mol}$$, how much heat is produced from the reaction of 155.0 g of NH$$_3$$?

Accepted Answer

$$-2058 kJ$$

Question 5

Which of the following is a state function?

Accepted Answer

Internal energy ($$U)$$

Question 6

A block of copper of unknown mass at 65.4°C is placed in 95.7 g of water at 22.7°C. The final temperature is 24.2°C. If the specific heat of copper is $$0.385\ 	ext{J/g}^\circ	ext{C}$$ and water is $$4.184\ 	ext{J/g}^\circ	ext{C}$$, what is the mass of the copper block?

Accepted Answer

95.7 g

Question 7

Which of the following would have a standard enthalpy of formation ($$\Delta H_f^\circ) of $$zero?

Accepted Answer

$$	ext{Hg}(l)$$

Question 8

Which equation correctly relates the change in internal energy ($$\Delta U) to $$heat ($$q) $$and work ($$w$$)?

Accepted Answer

$$\Delta U = q + w$$

Question 9

A 55.0 g aluminum block initially at 27.5°C absorbs 725 J of heat. What is the final temperature of the aluminum? ($$C_s = 0.903\ 	ext{J/g}^\circ	ext{C})$$

Accepted Answer

36.1°C

Question 10

Which of the following statements about exothermic reactions is correct?

Accepted Answer

The system releases heat to the surroundings.

Question 11

Which of the following best describes the difference between specific heat capacity and heat capacity?

Accepted Answer

Specific heat capacity is the amount of heat required to raise the temperature of 1 g of a substance by 1°C, while heat capacity is the amount of heat required to raise the temperature of an object by 1°C.

Question 12

If the direction of a chemical reaction is reversed, what happens to the enthalpy change ($$\Delta H_{rxn}$$)?

Accepted Answer

It changes sign.

Question 13

Which of the following is true at thermal equilibrium between a system and its surroundings?

Accepted Answer

There is no net heat flow between the system and surroundings.

Question 14

A chemical handwarmer uses the reaction $$4	ext{Fe}(s) + 3	ext{O}_2(g) ightarrow 2	ext{Fe}_2	ext{O}_3(s). If$$ $$\Delta H_f^\circ$$ for $$	ext{Fe}_2	ext{O}_3(s) is$$ $$-824.2 kJ/$$mol and for $$	ext{Fe}(s)$$ and $$	ext{O}_2(g) is $$zero, what is $$\Delta H_{rxn}^\circ$$ for the reaction?

Accepted Answer

$$-1648.4 kJ$$

Question 15

Which of the following is NOT a standard state for the element listed?

Accepted Answer

$$	ext{Na}(l)$$

Question 16

Which of the following equations correctly expresses the amount of heat ($$q) $$absorbed or released by a substance?

Accepted Answer

$$q = mC_s\Delta T$$

Question 17

A bomb calorimeter is used to measure the heat of combustion of a substance. Which condition is true for the system during the measurement?

Accepted Answer

Constant volume

Question 18

Which of the following best describes an endothermic reaction?

Accepted Answer

The system absorbs heat from the surroundings.

Question 19

Which of the following is the correct formula for pressure-volume work done by a system?

Accepted Answer

$$w = -P\Delta V$$

Question 20

Which of the following statements about Hess's Law is correct?

Accepted Answer

The enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps.

Chapter 6: Thermochemistry – Energy and Chemical Reactions

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