Question 1

Which of the following statements best describes a state function in thermochemistry?

Accepted Answer

A property that depends only on the initial and final states, not on the path taken.

Question 2

A student rides a bicycle from CHEM1050 to Signal Hill, while another drives a car along the same route. Which of the following is a state variable for both students?

Accepted Answer

Altitude at Signal Hill

Question 3

If a system absorbs 150 J of heat and does 35 J of work by expanding, what is the change in internal energy ($$\Delta U) of $$the system?

Accepted Answer

$$\Delta U = 115\ \mathrm{J}$$

Question 4

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

Accepted Answer

$$\Delta U = q + w$$

Question 5

A 50.0 g piece of aluminum at $$95.0^\circ\mathrm{C} is $$dropped into 200 g of water at $$25.0^\circ\mathrm{C}. If $$the specific heat of aluminum is $$0.903\ \mathrm{J}\,\mathrm{g}^{-1}\mathrm{K}^{-1}$$ and water is $$4.184\ \mathrm{J}\,\mathrm{g}^{-1}\mathrm{K}^{-1}$$, what is the final temperature ($$T_f) of $$the system? (Assume no heat loss to surroundings.)

Accepted Answer

$$T_f \approx 30.2^\circ\mathrm{C}$$

Question 6

Which of the following best describes the surroundings in the scenario where ice cubes are added to water and melt?

Accepted Answer

The glass of water that loses energy to the ice cubes

Question 7

What is the sign of $$\Delta U_{sys}$$ when ice cubes melt in water and absorb energy from the water?

Accepted Answer

$$\Delta U_{sys} \u003e 0$$

Question 8

Which formula correctly expresses the relationship between heat capacity ($$C$$), heat ($$q$$), and temperature change ($$\Delta T$$)?

Accepted Answer

$$q = C 	imes \Delta T$$

Question 9

A copper saucepan (500 g) containing 1.00 kg of water is heated from $$25.0^\circ\mathrm{C} to$$ $$100.0^\circ\mathrm{C}. If $$the specific heat of copper is $$0.385\ \mathrm{J}\,\mathrm{g}^{-1}\mathrm{K}^{-1}$$ and water is $$4.184\ \mathrm{J}\,\mathrm{g}^{-1}\mathrm{K}^{-1}$$, what is the total heat required?

Accepted Answer

$$q \approx 326,000\ \mathrm{J}$$

Question 10

Which of the following statements about specific heat capacity ($$C_s) is $$correct?

Accepted Answer

It is the amount of heat required to raise the temperature of 1 g of a substance by 1 K.

Question 11

Why do large bodies of water moderate temperature variations in coastal regions?

Accepted Answer

Water has a high specific heat capacity, so it absorbs and releases heat slowly.

Question 12

Which equation is used to calculate the work done by a gas during expansion at constant pressure?

Accepted Answer

$$w = -P \Delta V$$

Question 13

During the combustion of octane in a car engine, which of the following best describes the energy changes?

Accepted Answer

Internal energy is lost as both heat and work.

Question 14

A gas expands from 1.00 L to 1.50 L against a constant pressure of 2.00 bar. What is the work done by the gas? (1 bar = $$10^5 Pa$$, 1 L = $$10^{-3} m$^3)$$

Accepted Answer

$$w = -100\ \mathrm{J}$$

Question 15

Which of the following is NOT a state function?

Accepted Answer

Work done to reach a destination

Question 16

For the reaction $$\mathrm{CH}_4(g) + 2\mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g) + 2\mathrm{H}_2O(l) at 298 K$$, what is the work done per mole of methane if the volume of water produced is negligible? ($$R = 8.314\ \mathrm{J}\,\mathrm{mol}^{-1}\mathrm{K}^{-1})$$

Accepted Answer

$$w = -4,955\ \mathrm{J}$$

Question 17

Which of the following best describes the process of thermal equilibrium?

Accepted Answer

When two objects in contact reach the same temperature and no net heat flows between them.

Question 18

If the temperature of a system increases from $$283.2\ \mathrm{K} to$$ $$373.2\ \mathrm{K}$$, what is $$\Delta T$$?

Accepted Answer

$$\Delta T = 90.0\ \mathrm{K}$$

Question 19

Which of the following equations is used to calculate the heat required to raise the temperature of a substance using its specific heat capacity?

Accepted Answer

$$q = m 	imes C_s 	imes \Delta T$$

Thermochemistry 6.2: Internal Energy, State Functions, Heat, and Work

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