Question 1

Which of the following best describes the difference between heat ($$q) $$and temperature ($$T$$)?

Accepted Answer

Heat is the energy transferred between objects due to a temperature difference, while temperature is a measure of the average kinetic energy of particles.

Question 2

A chemical reaction in a beaker feels cold to the touch. Which of the following statements is true about the reaction?

Accepted Answer

The reaction is endothermic and absorbs heat from the surroundings.

Question 3

Which of the following equations correctly relates the change in internal energy ($$\Delta U) of a $$system to heat ($$q) $$and work ($$w$$)?

Accepted Answer

$$\Delta U = q + w$$

Question 4

A gas is compressed in a cylinder by a piston. During the compression, 150 J of work is done on the gas, and the gas releases 50 J of heat to the surroundings. What is the change in internal energy ($$\Delta U) of $$the gas?

Accepted Answer

$$\Delta U = 100 \ \mathrm{J}$$

Question 5

Which of the following best describes an open system in thermochemistry?

Accepted Answer

A system that can exchange both energy and matter with its surroundings.

Question 6

Which of the following is the correct definition of enthalpy ($$H$$)?

Accepted Answer

$$H = U + PV$$

Question 7

A student mixes 50.0 g of water at $$25.0^\circ \mathrm{C}$$ with 50.0 g of water at $$75.0^\circ \mathrm{C} in a $$calorimeter. Assuming no heat is lost to the surroundings, what is the final temperature of the mixture?

Accepted Answer

$$50.0^\circ \mathrm{C}$$

Question 8

Which of the following statements about state functions is correct?

Accepted Answer

State functions depend only on the initial and final states, not on the path taken.

Question 9

Which of the following is the correct expression for the heat ($$q) $$absorbed or released by a substance in terms of its mass ($$m$$), specific heat capacity ($$c$$), and temperature change ($$\Delta T$$)?

Accepted Answer

$$q = mc\Delta T$$

Question 10

Which of the following best describes Hess's Law?

Accepted Answer

The enthalpy change of a reaction is independent of the pathway between initial and final states.

Question 11

A reaction has $$\Delta H = -250 \ \mathrm{kJ}. $$Which of the following statements is true?

Accepted Answer

The reaction is exothermic and releases 250 kJ of heat.

Question 12

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 13

In a coffee-cup calorimeter, a student dissolves 2.00 g of NaOH in 100.0 g of water, causing the temperature to rise from $$25.0^\circ \mathrm{C} to$$ $$27.5^\circ \mathrm{C}. If $$the specific heat capacity of water is $$4.18 \ \mathrm{J} / \mathrm{g} \cdot ^\circ \mathrm{C}$$, what is the heat absorbed by the solution?

Accepted Answer

$$1,045 \ \mathrm{J}$$

Question 14

Which of the following best explains why the enthalpy of formation of an element in its standard state is zero?

Accepted Answer

Because the element is already in its most stable form under standard conditions.

Question 15

Which of the following is the correct unit for enthalpy change ($$\Delta H) in $$the SI system?

Accepted Answer

$$\mathrm{J}$$

Question 16

A reaction has $$\Delta H = +150 \ \mathrm{kJ}. $$Which of the following is true about this reaction?

Accepted Answer

The reaction is endothermic and absorbs 150 kJ of heat.

Question 17

Which of the following best describes the first law of thermodynamics?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 18

Which of the following is a correct application of Hess's Law?

Accepted Answer

The enthalpy change for the overall reaction is the sum of the enthalpy changes for the individual steps.

Question 19

Which of the following statements about calorimetry is correct?

Accepted Answer

Calorimetry measures the heat transferred during a chemical or physical process.

Question 20

A chemical reaction occurs in a bomb calorimeter, causing the temperature of the calorimeter to increase by $$2.00^\circ \mathrm{C}. If $$the heat capacity of the calorimeter is $$5.00 \ \mathrm{kJ} / ^\circ \mathrm{C}$$, what is the heat released by the reaction?

Accepted Answer

$$10.0 \ \mathrm{kJ}$$

Chapter 5: Thermochemistry – Study Notes

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