Q: A 2.0 kg ball is moving at 3.0 m/s. What is its kinetic energy?

$$KE = \frac{1}{2} \times 2.0 \times (3.0)^2$ = 18.0\ J$$

Q: Which equation correctly relates heat, mass, specific heat capacity, and temperature change?

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

Q: If 100 g of water absorbs 418 J of heat, what is the temperature change? (Specific heat of water = 4.18 J/g·°C)

$$\Delta T = \frac{418}{100 \times 4.18} = 1.0\ ^\circ C$$

Q: 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 final equilibrium temperature is 17.5°C, what is the heat lost by the aluminum? (Specific heat of Al = 0.903 J/g·°C)

$$q = 32.5 \times 0.903 \times (17.5 - 45.8) = -857\ J$$

Q: Which of the following conversions is correct?

1 kilowatt-hour (kWh) = $$3.60 \times 10^6$ joules (J)

Question 1

Which of the following best describes the difference between potential energy and kinetic energy, as illustrated by a compressed spring and a moving ball?

Accepted Answer

Potential energy is stored energy due to position, while kinetic energy is energy of motion.

Question 2

A 2.0 kg ball is moving at 3.0 m/s. What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2} 	imes 2.0 	imes (3.0)^2$ = 18.0\ J$$

Question 3

Which equation correctly relates heat, mass, specific heat capacity, and temperature change?

Accepted Answer

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

Question 4

If 100 g of water absorbs 418 J of heat, what is the temperature change? (Specific heat of water = 4.18 J/g·°C)

Accepted Answer

$$\Delta T = \frac{418}{100 	imes 4.18} = 1.0\ ^\circ C$$

Question 5

Which statement best describes the First Law of Thermodynamics?

Accepted Answer

Energy can neither be created nor destroyed, only transferred or transformed.

Question 6

A chemical reaction occurs in a coffee-cup calorimeter. The temperature of the solution increases. What can you conclude about the reaction?

Accepted Answer

The reaction is exothermic; heat is released by the system.

Question 7

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

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 final equilibrium temperature is 17.5°C, what is the heat lost by the aluminum? (Specific heat of Al = 0.903 J/g·°C)

Accepted Answer

$$q = 32.5 	imes 0.903 	imes (17.5 - 45.8) = -857\ J$$

Question 9

Which process is represented by a negative change in internal energy ($$\Delta E \u003c 0) $$for the system?

Accepted Answer

Energy flows from the system into the surroundings.

Question 10

Which of the following conversions is correct?

Accepted Answer

1 kilowatt-hour (kWh) = $$3.60 	imes 10^6$ joules (J)

Question 11

Which equation correctly expresses the relationship between enthalpy change and heat at constant pressure?

Accepted Answer

$$\Delta H = q_P$$

Question 12

A reaction is reversed. What happens to the enthalpy change ($$\Delta H$$)?

Accepted Answer

The sign of $$\Delta H$$ changes.

Question 13

Which of the following statements about bond energies is correct?

Accepted Answer

Bond breaking is endothermic and bond making is exothermic.

Question 14

Calculate the enthalpy change for the reaction: $$2H_2(g) + O_2$(g) \rightarrow 2H_2O(g)$$ using the following bond energies: $$H-H = 436\ kJ/mol$$, $$O=O = 498\ kJ/mol$$, $$O-H = 463\ kJ/mol.$$

Accepted Answer

$$\Delta H = [2 	imes 436 + 1 	imes 498] - [4 	imes 463] = -484\ kJ$$

Question 15

Which of the following best describes an endothermic reaction?

Accepted Answer

Heat flows from the surroundings to the system, and the surroundings feel cold.

Question 16

Which equation is used to calculate the standard enthalpy change for a reaction using enthalpies of formation?

Accepted Answer

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

Question 17

A 13.2 kg tank of propane ($$C_3H_8) is $$completely combusted. How much heat is released? ($$\Delta H_{rxn} = -2044\ kJ$$ per mole $$C_3H_8$$; molar mass $$C_3H_8 = 44.1\ g/mol)$$

Accepted Answer

$$	ext{Heat released} = \frac{13200}{44.1} 	imes (-2044) = -611,000\ kJ$$

Question 18

Which of the following statements about heat capacity is correct?

Accepted Answer

The heat capacity of an object depends on both its mass and the type of material.

Thermochemistry: Energy, Heat, and Enthalpy in Chemical Systems

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