Question 1

A 21.0 g rock rolls down a hill at a speed of 105.0 m/s. What is the kinetic energy of the rock? (Use $E_k = \frac{1}{2}mv^2$ and $1 	ext{ kg} = 1000 	ext{ g}$)

Accepted Answer

$115.8 	ext{ J}$

Question 2

Which of the following best describes an isolated system?

Accepted Answer

Neither energy nor matter can be exchanged with the surroundings.

Question 3

The electrostatic potential energy between two charges $Q_1$ and $Q_2$ separated by a distance $d$ is given by $E_{el} = \frac{\kappa Q_1 Q_2}{d}$. What happens to $E_{el}$ as $d$ increases?

Accepted Answer

$E_{el}$ approaches zero.

Question 4

A system absorbs 140 J of heat from the surroundings and does 85 J of work on the surroundings. What is the change in internal energy ($\Delta E$) of the system?

Accepted Answer

$+55 	ext{ J}$

Question 5

Which of the following is a state function?

Accepted Answer

Internal energy ($E$)

Question 6

During a chemical reaction, the system releases 672 kJ of heat to the surroundings and does 236 kJ of work on the surroundings. What is $\Delta E$ for the system?

Accepted Answer

$-908 	ext{ kJ}$

Question 7

Which of the following statements is true about exothermic reactions?

Accepted Answer

The system loses heat and $\Delta H$ is negative.

Question 8

Calculate the work done (in J) when the volume of a system contracts from 1.55 L to 0.85 L at a constant pressure of 0.985 atm. ($1 	ext{ L-atm} = 101.3 	ext{ J}$, $w = -P\Delta V$)

Accepted Answer

$+69.85 	ext{ J}$

Question 9

Which of the following best describes enthalpy ($H$)?

Accepted Answer

$H = E + PV$

Question 10

If the enthalpy of the products is less than the enthalpy of the reactants, what can be said about the reaction?

Accepted Answer

The reaction is exothermic and $\Delta H$ is negative.

Question 11

How much heat is released when 4.50 g of methane gas ($CH_4$) is burned in a constant-pressure system? ($CH_4 + 2 O_2 ightarrow CO_2 + 2 H_2O$, $\Delta H = -890 	ext{ kJ}$, $M_{CH_4} = 16 	ext{ g/mol}$)

Accepted Answer

$-250.3 	ext{ kJ}$

Question 12

Which of the following is true regarding the specific heat capacity ($C_s$) of water compared to metals?

Accepted Answer

Water has a higher specific heat capacity and is more resistant to temperature changes.

Question 13

A 25.0 g sample of an unknown metal is heated to 100.0°C and then placed in water, releasing -669.4 J of heat as it cools to 30.0°C. What is the specific heat ($C_s$) of the metal?

Accepted Answer

$0.383 \frac{J}{g \cdot ^\circ C}$

Question 14

Which of the following is NOT a guideline when using thermochemical equations?

Accepted Answer

The enthalpy change for a reaction is independent of the states of reactants and products.

Question 15

How much energy (in kJ) does it take to raise the body temperature of a 50 kg person by 2.5°C? (Assume $C_s = 3 \frac{J}{g \cdot ^\circ C}$)

Accepted Answer

$375 	ext{ kJ}$

Question 16

Which of the following best describes the difference between heat and work in thermodynamics?

Accepted Answer

Heat is energy transferred due to temperature difference; work is energy transferred when an object is moved by a force.

Question 17

Which of the following is true about the sign conventions for $q$, $w$, and $\Delta E$?

Accepted Answer

A positive $q$ means the system gains heat.

Chapter 5: Thermochemistry – Study Notes for General Chemistry II

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