Question 1

Which of the following statements best describes a state function in thermodynamics?

Accepted Answer

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

Question 2

A chemical reaction occurs in an open container at constant pressure. Which thermodynamic quantity is most directly measured under these conditions?

Accepted Answer

Enthalpy change ($$\Delta H)$$

Question 3

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

Accepted Answer

$$\Delta E = q + w$$

Question 4

During a chemical reaction, the system absorbs 75 kJ of heat and does 25 kJ of work on the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = 50 kJ$$

Question 5

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 6

A reaction occurs in which the system evolves 100 kJ of heat and has 50 kJ of work done on it. What is $$\Delta E$$?

Accepted Answer

$$\Delta E = -50 kJ$$

Question 7

Which statement best summarizes the First Law of Thermodynamics?

Accepted Answer

The total energy of the universe is a constant; energy can be converted from one form to another, but cannot be created or destroyed.

Question 8

Which formula is used to calculate the work done by a system during expansion against a constant external pressure?

Accepted Answer

$$w = -P \Delta V$$

Question 9

A chemical reaction causes the volume of a system to expand from 120.0 mL to 455.8 mL against an external pressure of 3.20 atm. Calculate the work done by the system. ($$1\ 	ext{L atm} = 101\ 	ext{J})$$

Accepted Answer

$$w = -0.109 kJ$$

Question 10

For a reaction involving only liquids and solids, which statement is most accurate regarding the relationship between $$\Delta H$$ and $$\Delta E$$?

Accepted Answer

$$\Delta H is $$approximately equal to $$\Delta E$$ because $$P \Delta V is $$negligible.

Question 11

Which of the following best describes the enthalpy change ($$\Delta H) at $$constant pressure?

Accepted Answer

It is the heat lost or gained by the system.

Question 12

In a reaction where $$\Delta V is $$non-negligible and gases are involved, which statement is true?

Accepted Answer

$$\Delta H is $$typically much larger than $$P \Delta V.$$

Question 13

Which of the following is a correct expression for enthalpy ($$H$$)?

Accepted Answer

$$H = E + PV$$

Question 14

A reaction occurs at constant pressure and results in a significant increase in volume. Which term accounts for the work done by the system?

Accepted Answer

$$w = -P \Delta V$$

Question 15

Why is enthalpy ($$\Delta H) $$often used instead of internal energy ($$\Delta E) in $$chemical experiments?

Accepted Answer

Because enthalpy is easier to measure under constant pressure conditions.

Question 16

Which of the following best describes the energy transfer when a system does work on the surroundings?

Accepted Answer

Energy is transferred out of the system; $$w \u003c 0.$$

Question 17

Which of the following reactions would have $$\Delta V \approx 0$$ and therefore $$\Delta H \approx \Delta E$$?

Accepted Answer

$$H_2SO_4(aq) + 2KOH(aq) \rightarrow K_2SO_4(aq) + 2H_2O(l)$$

Question 18

If a system absorbs heat from the surroundings and the surroundings do work on the system, what are the signs of $$q$$ and $$w$$?

Accepted Answer

$$q \u003e 0$$, $$w \u003e 0$$

Question 19

Which of the following best explains why measuring internal energy directly is impractical for chemical systems?

Accepted Answer

Because the number of particles in chemical systems is so great that measuring all kinetic and potential energies is not feasible.

Internal Energy, Enthalpy, and Thermodynamics in Chemical Reactions

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