Question 1

Which of the following statements best describes the difference between internal energy and heat?

Accepted Answer

Heat is the energy transferred from one body or location to another due to a temperature difference, while internal energy is the total energy contained within a system.

Question 2

A gas expands from 0.0 L to 2.5 L against an external pressure of 1.0 atm. How much work (in J) is done by the gas during this expansion? ($w = -P_{ext} \Delta V$; 1 L·atm = 101.3 J)

Accepted Answer

$w = -253.25$ J

Question 3

Which of the following processes is exothermic?

Accepted Answer

Combustion of gasoline in a car engine.

Question 4

If a system absorbs 565 J of heat and expands from 1.00 L to 0.85 L against an external pressure of 1.0 atm, what is the change in internal energy ($\Delta E$) of the system? ($w = -P_{ext} \Delta V$; 1 L·atm = 101.3 J)

Accepted Answer

$\Delta E = 580.2$ J

Question 5

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

Accepted Answer

$\Delta E = w + q$

Question 6

A 32.5-g cube of aluminum at 45.8 °C is submerged into 155.3 g of water at 15.4 °C. Assuming no heat is lost, what is the final temperature of both substances at thermal equilibrium? ($q_{Al} = -q_{H_2O}$, $q = mC\Delta T$, $C_{Al} = 0.897$ J/g·°C, $C_{H_2O} = 4.18$ J/g·°C)

Accepted Answer

The final temperature is approximately 17.1 °C.

Question 7

Which of the following is true for an endothermic reaction?

Accepted Answer

$q$ is positive and heat is absorbed from the surroundings.

Question 8

Using Hess's Law, calculate $\Delta H_{rxn}$ for the reaction: $\mathrm{Fe_2O_3(s) + 3 CO(g) \rightarrow 2 Fe(s) + 3 CO_2(g)}$ given: $\mathrm{2 Fe(s) + 3 O_2(g) \rightarrow 2 Fe_2O_3(s)}$ $\Delta H = -824.2$ kJ and $\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}$ $\Delta H = -393.5$ kJ.

Accepted Answer

$\Delta H_{rxn} = -282.7$ kJ

Question 9

Which calorimeter is best suited for measuring $\Delta E_{rxn}$ at constant volume?

Accepted Answer

Bomb calorimeter

Question 10

A 0.103 g sample of Zn reacts with excess HCl in a coffee-cup calorimeter, raising the temperature of 50.0 mL of solution from 22.5 °C to 23.7 °C. What is the enthalpy change ($\Delta H_{rxn}$) for the reaction? (Density = 1.0 g/mL, $C = 4.18$ J/g·°C)

Accepted Answer

$\Delta H_{rxn} = -251$ J

Question 11

Which of the following best explains why lattice energy increases as ionic charge increases?

Accepted Answer

Lattice energy increases because the electrostatic attraction between ions increases with higher charge.

Question 12

Which formula is used to calculate the heat absorbed or released by a substance?

Accepted Answer

$q = mC\Delta T$

Question 13

Which of the following reactions is most likely to have a positive $\Delta H_{rxn}$?

Accepted Answer

Evaporation of water

Question 14

If the temperature of a system increases and the surroundings decrease, what is the sign of $\Delta E_{sys}$?

Accepted Answer

$\Delta E_{sys} > 0$

Question 15

Which of the following statements about work ($w$) in thermodynamics is correct?

Accepted Answer

Work is negative when a system expands against an external pressure.

Question 16

Which of the following is the correct expression for pressure-volume work?

Accepted Answer

$w = -P_{ext} \Delta V$

Question 17

Which of the following best describes the energy changes in an exothermic reaction?

Accepted Answer

Energy flows from the system to the surroundings.

Question 18

Which of the following is NOT a form of energy transfer discussed in thermodynamics?

Accepted Answer

Internal energy

Question 19

A person packs two identical coolers for a picnic, placing twenty-four 12-ounce soft drinks and 5 pounds of ice in each. However, the drinks put into cooler A were refrigerated several hours before, while those in cooler B were at room temperature. After several hours, most of the ice in cooler B has melted. Which principle explains this observation?

Accepted Answer

The drinks in cooler B absorbed more heat from the ice, causing it to melt.

Chapter 9: Internal Energy, Heat, and Work – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards