Question 1

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

Accepted Answer

Kinetic energy is associated with the motion of objects or molecules, while potential energy is related to how energy is stored due to position or arrangement.

Question 2

A 50.0 g piece of copper (specific heat $$c = 0.385 \ \mathrm{J/g\cdot ^\circ C}) is $$heated from $$25.0\ ^\circ \mathrm{C} to$$ $$100.0\ ^\circ \mathrm{C}. $$How much heat ($$q) is $$absorbed by the copper?

Accepted Answer

$$q = (50.0)(0.385)(100.0 - 25.0) = 1443.75\ \mathrm{J}$$

Question 3

Which equation correctly relates heat ($$q$$), mass ($$m$$), specific heat ($$c$$), and temperature change ($$\Delta T$$)?

Accepted Answer

$$q = mc\Delta T$$

Question 4

In a calorimetry experiment, a hot metal is placed in cooler water. If the system is perfectly insulated, which of the following is true?

Accepted Answer

The heat lost by the metal equals the heat gained by the water.

Question 5

Which of the following statements about exothermic and endothermic processes is correct?

Accepted Answer

Exothermic processes release heat to the surroundings, while endothermic processes absorb heat from the surroundings.

Question 6

A reaction occurs at constant pressure and releases $$250\ \mathrm{kJ} of $$heat. What is the sign and value of $$\Delta H$$ for this reaction?

Accepted Answer

$$\Delta H = -250\ \mathrm{kJ}$$

Question 7

Which of the following best describes the law of conservation of energy as it applies to chemical reactions?

Accepted Answer

The total energy of the system and surroundings remains constant; energy is transferred but not created or destroyed.

Question 8

Which of the following is the correct expression for the kinetic energy ($$KE) of an $$object with mass $$m$$ and velocity $$v$$?

Accepted Answer

$$KE = \frac{1}{2}mv^2$

Question 9

A 100.0 g piece of metal at $$75.0\ ^\circ \mathrm{C} is $$placed in 100.0 g of water at $$25.0\ ^\circ \mathrm{C}. $$The final temperature is $$32.5\ ^\circ \mathrm{C}. If $$the specific heat of water is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, how much heat did the water absorb?

Accepted Answer

$$q = (100.0)(4.18)(32.5 - 25.0) = 3135\ \mathrm{J}$$

Question 10

Which of the following best describes the meaning of specific heat capacity?

Accepted Answer

The amount of heat required to raise the temperature of 1 g of a substance by $$1\ ^\circ \mathrm{C}.$$

Question 11

Which of the following is true about the sign of $$q ($$heat) in thermochemistry?

Accepted Answer

$$q is $$positive when heat is absorbed by the system.

Question 12

Which of the following is an example of an endothermic process?

Accepted Answer

Melting of ice to form liquid water.

Question 13

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

Accepted Answer

$$\Delta U = q + w$$

Question 14

Which of the following best describes Hess's Law?

Accepted Answer

The enthalpy change for a reaction is independent of the pathway between initial and final states.

Question 15

Given the following reactions and enthalpies:

$$2SO_2(g) + O_2$(g) \rightarrow 2SO_3(g)\ \Delta H = -198\ \mathrm{kJ}$$

$$SO_3(g$$) \rightarrow $$SO_2(g$$) + \frac{1}{2}$$O_2(g$$)\ \Delta H = +99\ \mathrm{kJ}$$

What is the enthalpy change for the reaction SO_2$(g) + \frac{1}{2}O_2$(g) \rightarrow SO_3$(g)$$?

Accepted Answer

$$\Delta H = -99\ \mathrm{kJ}$$

Question 16

Which of the following is true about the relationship between enthalpy ($$\Delta H) $$and heat ($$q) at $$constant pressure?

Accepted Answer

$$\Delta H = q_p$$

Question 17

Which of the following best describes the standard enthalpy of formation ($$\Delta H_f^\circ$$)?

Accepted Answer

The enthalpy change for producing 1 mole of a compound from its elements in their standard states.

Question 18

Which of the following is a correct interpretation of the equation $$q_{object} + q_{surroundings} = 0 in $$calorimetry?

Accepted Answer

The heat lost by the object is equal in magnitude and opposite in sign to the heat gained by the surroundings.

Question 19

Which of the following is NOT a way to increase a system's energy?

Accepted Answer

Allowing the system to do work on the surroundings.

Unit 5: Thermochemistry – Energy, Heat, and Enthalpy in Chemical Processes

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