Question 1

Which of the following 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 closed system and releases 250 J of heat to the surroundings while the system does 100 J of work on the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = -350\ \mathrm{J}$$

Question 3

Which of the following statements about state functions is correct?

Accepted Answer

Internal energy (E) is a state function, but work (w) and heat (q) are not.

Question 4

Which of the following best describes an exothermic process?

Accepted Answer

The system releases heat to the surroundings.

Question 5

A reaction is carried out in a bomb calorimeter. Which of the following is true about the measurement?

Accepted Answer

The reaction occurs at constant volume and measures $$\Delta E.$$

Question 6

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

Accepted Answer

$$\Delta E = q + w$$

Question 7

A 100.0 g sample of water is heated from 25.0°C to 75.0°C. What is the amount of heat absorbed by the water? (Specific heat of water = $$4.184\ \mathrm{J/g\cdot K})$$

Accepted Answer

$$q = 20,920\ \mathrm{J}$$

Question 8

Which of the following is true about enthalpy ($$H$$)?

Accepted Answer

The enthalpy change for a reaction depends on the states of reactants and products.

Question 9

Which of the following best describes Hess’s Law?

Accepted Answer

The enthalpy change for a reaction is the sum of the enthalpy changes for each step in the reaction pathway.

Question 10

Given the following standard enthalpies of formation: $$\Delta H_f^\circ(CO$_2(g)) = -393.5$$\ \mathrm{kJ/mol}$$, $$\Delta H_f^\circ$$(H_2$O(l)) = -285.8\ \mathrm{kJ/mol}$$, $$\Delta H_f^\circ(C$_6H$$_{12}$$O_6(s)) = -1273$$\ \mathrm{kJ/mol}$$, calculate the standard enthalpy change for the combustion of glucose: C_6H$$_{12}$$O_6(s) + 6O_2(g$$) \rightarrow 6CO_2(g) + 6H_2O(l)$.

Accepted Answer

$$\Delta H^\circ = -2802\ \mathrm{kJ}$$

Question 11

Which of the following statements about bond enthalpy is correct?

Accepted Answer

Bond enthalpy is always positive because energy is required to break bonds.

Question 12

Which of the following best describes an open system?

Accepted Answer

A system that can exchange both heat and mass with its surroundings.

Question 13

A reaction in a coffee-cup calorimeter causes the temperature of the solution to decrease. Which of the following is true?

Accepted Answer

The reaction is endothermic.

Question 14

Which of the following is the correct expression for the enthalpy change of a reaction using standard enthalpies of formation?

Accepted Answer

$$\Delta H^\circ = \sum n \Delta H_f^\circ(	ext{products}) - \sum m \Delta H_f^\circ(	ext{reactants})$$

Question 15

Which of the following is a real-world example of an endothermic process?

Accepted Answer

Melting of ice in a drink.

Question 16

If the enthalpy change for a reaction is $$+150\ \mathrm{kJ}$$, which of the following statements is true?

Accepted Answer

The reaction is endothermic and absorbs 150 kJ of heat.

Question 17

Which of the following best explains why the enthalpy of reaction depends on the physical states of reactants and products?

Accepted Answer

Different physical states have different internal energies and enthalpies.

Question 18

Which of the following is the correct formula for calculating the heat absorbed or released by a substance?

Accepted Answer

$$q = m \cdot C_s \cdot \Delta T$$

Chapter 5: Thermochemistry – Study Notes for General Chemistry

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