Q: A reaction is performed in a bomb calorimeter and releases 5000 J of energy. If the calorimeter constant is 785 J/°C and the temperature increases by 6.37°C, what is the total heat absorbed by the calorimeter?

$$q = 785 \times 6.37 = 5000 \text{ J}$$

Q: Which of the following is the correct formula for calculating the enthalpy change of a reaction using standard enthalpies of formation ($$\Delta H_f^\circ$$)?

$$\Delta H_{rxn}^\circ = \sum \Delta H_f^\circ \text{(products)} - \sum \Delta H_f^\circ \text{(reactants)}$$

Question 1

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

Accepted Answer

A property that depends only on the initial and final states of a system, not on the path taken.

Question 2

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

Accepted Answer

$$\Delta E = q + w$$

Question 3

A bomb calorimeter is used to measure the energy released during the combustion of a sample at constant volume. Which of the following statements is true?

Accepted Answer

The heat measured equals the change in internal energy ($$\Delta E) of $$the reaction.

Question 4

Which formula is used to calculate the amount of heat ($$q) $$absorbed or released by a substance, given its mass ($$m$$), specific heat ($$C$$), and temperature change ($$\Delta T$$)?

Accepted Answer

$$q = mC\Delta T$$

Question 5

Which of the following best explains why water is an effective 'heat sponge' in calorimetry experiments?

Accepted Answer

Water has a high specific heat capacity, meaning it can absorb a large amount of heat with a small temperature change.

Question 6

In a coffee cup calorimeter, which condition is held constant during the measurement of enthalpy change ($$\Delta H$$)?

Accepted Answer

Pressure

Question 7

Which of the following equations correctly defines enthalpy ($$H$$)?

Accepted Answer

$$H = E + PV$$

Question 8

A reaction is performed in a bomb calorimeter and releases 5000 J of energy. If the calorimeter constant is 785 J/°C and the temperature increases by 6.37°C, what is the total heat absorbed by the calorimeter?

Accepted Answer

$$q = 785 	imes 6.37 = 5000 	ext{ J}$$

Question 9

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 10

When calculating the enthalpy change ($$\Delta H) $$for a reaction using Hess's Law, which of the following rules must be followed?

Accepted Answer

If you reverse a reaction, you must change the sign of $$\Delta H.$$

Question 11

Which of the following best describes the difference between kinetic and potential energy?

Accepted Answer

Kinetic energy is the energy of motion, while potential energy is stored energy due to position or composition.

Question 12

Which of the following reactions would produce significant work due to a change in volume ($$V) $$under constant pressure?

Accepted Answer

Zn (s) + 2 HCl (aq) $$\rightarrow$$ ZnCl$$_2 (aq) + H$_2 (g)$$

Question 13

Which equation is used to calculate the work ($$w) $$done by a gas during expansion or compression at constant pressure?

Accepted Answer

$$w = -P\Delta V$$

Question 14

Which of the following statements about specific heat ($$C) is $$correct?

Accepted Answer

Specific heat is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

Question 15

Which of the following is the correct formula for calculating the enthalpy change of a reaction using standard enthalpies of formation ($$\Delta H_f^\circ$$)?

Accepted Answer

$$\Delta H_{rxn}^\circ = \sum \Delta H_f^\circ 	ext{(products)} - \sum \Delta H_f^\circ 	ext{(reactants)}$$

Question 16

Which of the following best explains why the theoretical NaCl$$_2$$ molecule cannot exist in real life?

Accepted Answer

The energy required to remove a second electron from Na is much greater than the energy released in forming NaCl$$_2$$, making the process energetically unfavorable.

Question 17

Which of the following statements about bond enthalpy is correct?

Accepted Answer

Triple bonds generally have higher bond enthalpy than double or single bonds.

Question 18

Which equation is used to calculate the enthalpy change of a reaction using bond enthalpies?

Accepted Answer

$$\Delta H_{rxn} = \sum 	ext{Bond enthalpies of bonds broken} - \sum 	ext{Bond enthalpies of bonds formed}$$

Thermochemistry and Thermodynamics: Energy, Enthalpy, and Calorimetry

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