Question 1

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

Accepted Answer

Energy can be converted from one form to another, but cannot be created or destroyed.

Question 2

A chemical reaction occurs in a flask and the flask feels warm to the touch. What is the sign of $$\Delta H$$ for this reaction?

Accepted Answer

$$\Delta H is $$negative because the system releases heat.

Question 3

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 4

Which equation correctly relates the change in internal energy to heat and work?

Accepted Answer

$$\Delta E = q + w$$

Question 5

A system absorbs 100 J of heat from the surroundings and has 50 J of work done on it by the surroundings. What is $$\Delta E$$ for the system?

Accepted Answer

$$\Delta E = 150 J$$

Question 6

Which of the following processes is endothermic?

Accepted Answer

Electrolysis of water

Question 7

What is the formula for electrostatic potential energy between two charged particles?

Accepted Answer

$$E_{el} = \dfrac{kQ_1Q_2}{d}$$

Question 8

Which of the following best describes an isolated system?

Accepted Answer

A system that cannot exchange either energy or matter with its surroundings.

Question 9

If a gas expands against a constant external pressure, what is the sign of the work done by the system?

Accepted Answer

Work is negative because the system does work on the surroundings.

Question 10

Which equation defines enthalpy ($$H$$)?

Accepted Answer

$$H = E + PV$$

Question 11

A reaction releases 727 kJ of heat and does 105 kJ of work on the surroundings. What is $$\Delta E$$ for the system?

Accepted Answer

$$\Delta E = -832 kJ$$

Question 12

Which of the following is true about the sign conventions for heat ($$q) $$and work ($$w$$)?

Accepted Answer

Negative $$w$$ means work is done by the system on the surroundings.

Question 13

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 14

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

Accepted Answer

Kinetic energy is energy of motion, while potential energy is stored energy due to position.

Question 15

Which of the following reactions is exothermic?

Accepted Answer

Combustion of methane

Question 16

What is the unit of energy commonly used in chemistry, and how is it defined in terms of SI base units?

Accepted Answer

Joule ($$J$$), defined as $$1\ J = 1\ kg\ m^2$ / s^2$

Question 17

Which of the following best describes a closed system?

Accepted Answer

A system that can exchange energy but not mass with its surroundings.

Question 18

If a chemical reaction requires energy input to break bonds, what type of process is this?

Accepted Answer

Endothermic

Question 19

Which equation correctly expresses the change in enthalpy at constant pressure?

Accepted Answer

$$\Delta H = \Delta E + P \Delta V$$

Question 20

A student burns 20.1 g of oxygen ($$O_2) in a $$reaction where $$\Delta H = -2221 kJ $$for 5 moles of $$O_2. $$How much heat is released?

Accepted Answer

$$-279 kJ$$

Chemical Energy, Thermodynamics, and Enthalpy: Study Notes

Study Guide - Practice Questions