Question 1

Which of the following best describes the difference between a state function and a path function in thermodynamics?

Accepted Answer

A state function depends only on the initial and final states of a system, not on the path taken between them.

Question 2

A chemical reaction occurs in a flask, and you notice the flask gets 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 equation correctly represents the first law of thermodynamics for a closed system?

Accepted Answer

$$\Delta E = q + w$$

Question 4

A gas expands in a piston, doing 50 J of work on the surroundings and absorbing 30 J of heat from the surroundings. What is the change in internal energy $$\Delta E of $$the system?

Accepted Answer

$$\Delta E = -20\ \mathrm{J}$$

Question 5

Which of the following processes is endothermic?

Accepted Answer

Melting ice to form liquid water

Question 6

What is the correct expression for the enthalpy ($$H) of a $$system?

Accepted Answer

$$H = E + PV$$

Question 7

If a system absorbs 100 J of heat and has 50 J of work done on it by the surroundings, what is the value of $$\Delta E$$?

Accepted Answer

$$\Delta E = 150\ \mathrm{J}$$

Question 8

Which of the following statements about exothermic reactions is correct?

Accepted Answer

The system releases heat to the surroundings, and $$\Delta H is $$negative.

Question 9

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 10

A reaction occurs at constant pressure and the only work done is pressure-volume work. Which equation correctly relates the change in enthalpy to heat?

Accepted Answer

$$\Delta H = q_p$$

Question 11

Which of the following best describes an isolated system?

Accepted Answer

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

Question 12

Which of the following equations correctly gives the electrostatic potential energy between two point charges $$Q_1$$ and $$Q_2$$ separated by distance $$d$$?

Accepted Answer

$$E_{el} = \frac{k Q_1$ Q_2$}{d}$$

Question 13

Which of the following scenarios would result in a negative value for work ($$w) $$done by the system?

Accepted Answer

A gas expands against a constant external pressure.

Question 14

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 of the following is true?

Accepted Answer

The change in internal energy ($$\Delta E) is $$the same in both cases, but $$q$$ and $$w$$ are different.

Question 15

Which of the following best explains why forming a chemical bond is exothermic?

Accepted Answer

Energy is released as the system moves to a lower potential energy state.

Question 16

A sample of butane ($$C_4H_{10}) is $$burned in excess oxygen. If 20.1 g of $$O_2 is $$consumed and the enthalpy change for the reaction is $$\Delta H = -2221\ \mathrm{kJ}$$ per 5 moles of $$O_2$$, how much heat is released?

Accepted Answer

$$-279\ \mathrm{kJ}$$

Question 17

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

Accepted Answer

If the system absorbs heat, $$q is $$positive.

Question 18

Which of the following best describes a closed system?

Accepted Answer

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

Question 19

Which of the following is true about the internal energy ($$E) of a $$system?

Accepted Answer

We can only measure changes in internal energy ($$\Delta E$$), not its absolute value.

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

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