Question 1

Which of the following best describes a state function?

Accepted Answer

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

Question 2

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

Accepted Answer

$$\Delta E = q + w$$

Question 3

A chemical reaction in a beaker causes the temperature of the solution to decrease. Which statement is correct?

Accepted Answer

The reaction is endothermic and $$\Delta H \u003e 0.$$

Question 4

Which of the following is true about the sign of $$q$$ and $$w in $$thermodynamics?

Accepted Answer

If $$q is $$negative, the system loses heat.

Question 5

Which of the following best describes an exothermic process?

Accepted Answer

Heat is released by the system into the surroundings.

Question 6

What is the mathematical expression for pressure-volume work done by a gas?

Accepted Answer

$$w = -P \Delta V$$

Question 7

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

Accepted Answer

At constant pressure, the change in enthalpy equals the heat absorbed or released by the system.

Question 8

A reaction is carried out in a bomb calorimeter (constant volume). Which quantity is directly measured?

Accepted Answer

Change in internal energy ($$\Delta E)$$

Question 9

Which of the following is the correct formula for calculating the heat absorbed by water in a coffee-cup calorimeter?

Accepted Answer

$$q = C_s m \Delta T$$

Question 10

Which of the following is true about standard enthalpy of formation ($$\Delta H_f^\circ$$)?

Accepted Answer

It is the enthalpy change when 1 mole of a compound is formed from its elements in their standard states.

Question 11

Given the reaction: $$C_3H_8(g) + 5 O_2$(g) \rightarrow 3 CO_2$(g) + 4 H_2O(l)$$, which equation correctly expresses the enthalpy change using standard enthalpies of formation?

Accepted Answer

$$\Delta H_{rxn}^\circ = 3 \Delta H_f^\circ (CO_2$) + 4 \Delta H_f^\circ (H_2O) - \Delta H_f^\circ (C_3H_8)$$

Question 12

Which of the following is NOT a necessary component of a calorimeter?

Accepted Answer

A source of external heat

Question 13

If a reaction has $$\Delta H \u003e 0$$ and $$q \u003e 0 at $$constant pressure, which of the following is true?

Accepted Answer

The reaction is endothermic and absorbs heat.

Question 14

Which of the following statements about Hess's Law is correct?

Accepted Answer

The enthalpy change for a reaction is the sum of the enthalpy changes for each step in a series of reactions.

Question 15

Which of the following best describes the difference between heat ($$q) $$and work ($$w$$)?

Accepted Answer

Heat is random molecular motion, while work is organized molecular motion.

Question 16

A reaction is carried out at constant pressure and the system does 250 J of work on the surroundings while absorbing 500 J of heat. What is the change in internal energy ($$\Delta E$$)?

Accepted Answer

$$\Delta E = 250 	ext{ J}$$

Question 17

Which of the following is true about the enthalpy change for a reaction?

Accepted Answer

It depends on the states (phases) of the reactants and products.

Question 18

Which of the following is the correct expression for calculating the enthalpy change of a reaction using bond enthalpies?

Accepted Answer

$$\Delta H_{rxn} = \sum 	ext{(bond enthalpies of bonds broken)} - \sum 	ext{(bond enthalpies of bonds formed)}$$

Enthalpy, Internal Energy, and Calorimetry: Study Notes for General Chemistry

Study Guide - Practice Questions

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