Q: A system absorbs 50 kJ of heat from the surroundings and has 100 kJ of work done on it by the surroundings. What is the change in internal energy $$\Delta E$$?

$$\Delta E = 50 \text{ kJ} + 100 \text{ kJ} = 150 \text{ kJ}$$

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 it 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

Given the equation for electrostatic potential energy $$E_{el} = \frac{kQ_1Q_2}{d}$$, what happens to $$E_{el} as $$the distance $$d$$ between two oppositely charged ions increases?

Accepted Answer

$$E_{el}$$ approaches zero, indicating weaker attraction.

Question 5

Which process is endothermic?

Accepted Answer

Melting of ice into water

Question 6

A system absorbs 50 kJ of heat from the surroundings and has 100 kJ of work done on it by the surroundings. What is the change in internal energy $$\Delta E$$?

Accepted Answer

$$\Delta E = 50 	ext{ kJ} + 100 	ext{ kJ} = 150 	ext{ kJ}$$

Question 7

Which of the following best describes an isolated system?

Accepted Answer

It cannot exchange either energy or matter with its surroundings.

Question 8

At constant pressure, the change in enthalpy $$\Delta H$$ for a process is equal to:

Accepted Answer

The heat transferred to or from the system

Question 9

Which of the following equations correctly relates enthalpy ($$H$$), internal energy ($$E$$), pressure ($$P$$), and volume ($$V$$)?

Accepted Answer

$$H = E + PV$$

Question 10

A gas expands against a constant external pressure. What is the sign of the work ($$w) $$done by the system?

Accepted Answer

Negative, because the system does work on the surroundings.

Question 11

Which of the following is true about the change in internal energy ($$\Delta E) $$for a state function?

Accepted Answer

$$\Delta E$$ depends only on the initial and final states.

Question 12

Which of the following processes is exothermic?

Accepted Answer

Combustion of methane

Question 13

If a chemical reaction has $$\Delta H \u003c 0$$, which statement is true?

Accepted Answer

The reaction is exothermic and releases heat.

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.

Question 15

A battery is discharged by running a fan and by shorting it out. The final state of the battery is the same in both cases. Which statement is true?

Accepted Answer

The change in internal energy ($$\Delta E) is $$the same for both processes.

Question 16

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 17

A chemical reaction requires energy input to break bonds. What type of process is this?

Accepted Answer

Endothermic

Question 18

Which of the following best describes pressure-volume work?

Accepted Answer

Work done by a gas when it expands or contracts against an external pressure.

Question 19

If a system releases 622 kJ of heat and does 105 kJ of work on the surroundings, what is the change in internal energy $$\Delta E$$?

Accepted Answer

$$\Delta E = -622 	ext{ kJ} - 105 	ext{ kJ} = -727 	ext{ kJ}$$

Question 20

Which of the following best describes a closed system?

Accepted Answer

It can exchange energy but not matter with its surroundings.

Thermodynamics and Energy in Chemical Systems: Study Notes for General Chemistry

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