Question 1

Which of the following statements best describes the First Law of Thermodynamics?

Accepted Answer

The total energy of the universe is constant; energy can neither be created nor destroyed.

Question 2

A 50.0 g block of copper ($$C_s = 0.385\ \mathrm{J/g\cdot C}) is $$heated from $$20.0\ ^\circ\mathrm{C} to$$ $$80.0\ ^\circ\mathrm{C}. $$How much heat ($$q) is $$absorbed by the copper block?

Accepted Answer

$$q = 1155\ \mathrm{J}$$

Question 3

Which of the following is an example of potential energy?

Accepted Answer

A compressed spring.

Question 4

If a chemical reaction in a system releases heat to the surroundings and the system does $$-50\ \mathrm{J} of $$work, which of the following is true?

Accepted Answer

$$q \u003c 0$$, $$w \u003c 0$$, $$\Delta E \u003c 0$$

Question 5

Which equation correctly relates the change in internal energy ($$\Delta E) of a $$system to heat and work?

Accepted Answer

$$\Delta E = q + w$$

Question 6

A 32.5 g sample of aluminum ($$C_s = 0.903\ \mathrm{J/g\cdot C}) at$$ $$45.8\ ^\circ\mathrm{C} is $$placed in 105.3 g of water at $$15.4\ ^\circ\mathrm{C}$$ ($$C_s = 4.18\ \mathrm{J/g\cdot C}). $$What is the final temperature ($$T_f) at $$thermal equilibrium? (Assume no heat loss to surroundings.)

Accepted Answer

$$T_f \approx 17.9\ ^\circ\mathrm{C}$$

Question 7

Which of the following best describes a state function?

Accepted Answer

Its value depends only on the initial and final states, not the path taken.

Question 8

Which of the following is an intensive property?

Accepted Answer

Specific heat capacity ($$C_s)$$

Question 9

A bomb calorimeter is used to measure the energy change of a combustion reaction. If 1.010 g of sucrose ($$C_{12}H$$_{22}$$O_{11}) $$causes the temperature of the calorimeter to rise from $$24.92\ ^\circ\mathrm{C} to$$ $$28.33\ ^\circ\mathrm{C}$$, and the heat capacity of the calorimeter is $$4.90\ \mathrm{kJ}/^\circ\mathrm{C}$$, what is the energy change ($$q$) for the reaction?

Accepted Answer

$$q = 16.7\ \mathrm{kJ}$$

Question 10

Which of the following correctly describes the sign conventions for heat ($$q) $$and work ($$w) in $$thermodynamics?

Accepted Answer

Heat absorbed by the system: $$q \u003e 0$$; Work done by the system: $$w \u003c 0$$

Question 11

Which equation is used to calculate the amount of heat transferred to a substance given its heat capacity and temperature change?

Accepted Answer

$$q = C 	imes \Delta T$$

Question 12

A balloon is inflated from $$1.00\ \mathrm{L} to$$ $$1.85\ \mathrm{L}$$ against an external pressure of $$1.00\ \mathrm{atm}. $$How much work (in joules) is done by the system? ($$1\ \mathrm{L\cdot atm} = 101.3\ \mathrm{J})$$

Accepted Answer

$$w = -85.9\ \mathrm{J}$$

Question 13

Which of the following statements about enthalpy ($$\Delta H) is $$correct?

Accepted Answer

Enthalpy is the heat evolved in a chemical reaction at constant pressure.

Question 14

When 1 mole of butane combusts at constant pressure, it produces $$2658\ \mathrm{kJ} of $$heat and does $$3\ \mathrm{kJ} of $$work. What are the values of $$\Delta H$$ and $$\Delta E$$ for the combustion?

Accepted Answer

$$\Delta H = -2658\ \mathrm{kJ}$$, $$\Delta E = -2661\ \mathrm{kJ}$$

Question 15

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

Accepted Answer

$$\Delta H_f^\circ = 0$$

Question 16

A coffee cup calorimeter contains 100.0 mL of solution with a density of $$1.00\ \mathrm{g/mL}$$ and $$C_s = 4.18\ \mathrm{J/g\cdot C}. If $$the temperature rises from $$25.6\ ^\circ\mathrm{C} to$$ $$32.8\ ^\circ\mathrm{C}$$ after a reaction, what is the heat ($$q) $$absorbed by the solution?

Accepted Answer

$$q = 3018\ \mathrm{J}$$

Question 17

Which of the following best describes thermal equilibrium?

Accepted Answer

Two objects reach the same temperature and no net heat transfer occurs.

Question 18

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

Accepted Answer

$$w = -P \Delta V$$

Chapter 7: Thermochemistry and Energy in Chemical Systems

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