Q: Which equation correctly expresses the relationship between work, force, and distance?

$$w = \text{force} \times \text{distance}$$

Q: Which equation correctly relates the enthalpy change of a reaction to the enthalpies of formation of the products and reactants?

$$\Delta H^\circ_{rxn} = \sum n \Delta H^\circ_f(\text{products}) - \sum n \Delta H^\circ_f(\text{reactants})$$

Q: Which of the following is a correct formation reaction for $$CO(g)$$ from its elements in their standard states?

$$C(s, \text{graphite}) + \frac{1}{2} O_2$(g) \rightarrow CO(g)$$

Question 1

Which of the following best describes the difference between kinetic energy and potential energy in the context of chemical systems?

Accepted Answer

Kinetic energy is the energy of motion, while potential energy is the energy stored due to position or composition.

Question 2

A chemical hand warmer operates by the oxidation of iron. Which statement about this process is correct?

Accepted Answer

It is an exothermic reaction, releasing heat to your hand.

Question 3

Which equation correctly expresses the relationship between work, force, and distance?

Accepted Answer

$$w = 	ext{force} 	imes 	ext{distance}$$

Question 4

A 55.0 g aluminum block initially at 27.5°C absorbs 725 J of heat. The specific heat capacity of aluminum is $$0.897 \ 	ext{J/g} \cdot ^\circ	ext{C}. $$What is the final temperature of the block?

Accepted Answer

$$T_f = 42.1^\circ	ext{C}$$

Question 5

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 6

A system absorbs 559 J of heat and does 488 J of work on the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = 71 \ 	ext{J}$$

Question 7

Which of the following best describes the law of conservation of energy?

Accepted Answer

Energy cannot be created or destroyed, only transferred or transformed.

Question 8

A 32.5 g cube of aluminum at 45.8°C is placed in 105.3 g of water at 15.4°C. If the specific heat capacities are $$C_{s,Al} = 0.897 \ 	ext{J/g} \cdot ^\circ	ext{C}$$ and $$C_{s,H_2O} = 4.18 \ 	ext{J/g} \cdot ^\circ	ext{C}$$, which statement is true about the final temperature?

Accepted Answer

The final temperature will be closer to the initial temperature of the water.

Question 9

Which of the following processes is exothermic?

Accepted Answer

Water freezing in a freezer

Question 10

A cylinder equipped with a piston expands from 0.485 L to 1.245 L against an external pressure of 1.58 atm. How much work (in Joules) is done by the system? ($$1 \ 	ext{L} \cdot 	ext{atm} = 101.3 \ 	ext{J})$$

Accepted Answer

$$w = -122 \ 	ext{J}$$

Question 11

Which of the following best describes what happens to the temperature of a flask during an endothermic reaction?

Accepted Answer

The temperature falls.

Question 12

Which equation correctly relates the enthalpy change of a reaction to the enthalpies of formation of the products and reactants?

Accepted Answer

$$\Delta H^\circ_{rxn} = \sum n \Delta H^\circ_f(	ext{products}) - \sum n \Delta H^\circ_f(	ext{reactants})$$

Question 13

Which of the following is true about the standard enthalpy of formation ($$\Delta H^\circ_f) $$for a pure element in its standard state?

Accepted Answer

$$\Delta H^\circ_f is $$zero.

Question 14

Which of the following best describes the environmental impact of burning fossil fuels?

Accepted Answer

It contributes to air pollution, acid rain, and global warming.

Question 15

A bomb calorimeter contains 1.010 g of sucrose ($$C_{12}H$$_{22}$$O_{11}) $$and has a heat capacity of $$4.90 \ 	ext{kJ}/^\circ	ext{C}. If $$the temperature rises from $$24.92^\circ	ext{C} to$$ $$28.33^\circ	ext{C}$, what is the total heat absorbed by the calorimeter?

Accepted Answer

$$q_{cal} = 16.7 \ 	ext{kJ}$$

Question 16

Which of the following is a correct formation reaction for $$CO(g)$$ from its elements in their standard states?

Accepted Answer

$$C(s, 	ext{graphite}) + \frac{1}{2} O_2$(g) ightarrow CO(g)$$

Question 17

If a reaction is reversed, what happens to the sign of $$\Delta H$$?

Accepted Answer

It changes sign.

Question 18

Which of the following best explains why water is commonly used as a coolant in engines?

Accepted Answer

Water has a high specific heat capacity, so it can absorb a lot of heat without a large temperature increase.

Chapter 7: Thermochemistry – Energy and Chemical Reactions

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