Q: A 50.0 g sample of water is heated from 22.0°C to 28.8°C. Given the specific heat of water is $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}$$, how much heat was absorbed by the water?

$$1.42 \times 10^3$\ \mathrm{J}$$

Q: A 100.0 g sample of water is heated from 21.0°C to 37.0°C. How much heat is required? (Specific heat of water = $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$})$$

$$6.69 \times 10^3$\ \mathrm{J}$$

Q: If 1.00 kg of sucrose ($$C_{12}H$$_{22}$$O_{11}) is $$completely combusted and $$\Delta H = -5.65 \times 10^3$\ \mathrm{kJ\ $$mol^{-1}$$}$$, how much heat is released? (Molar mass of sucrose = $$342.3\ \mathrm{g\ $$mol^{-1}$$}$)

$$-1.65 \times 10^4$\ \mathrm{kJ}$$

Question 1

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

Accepted Answer

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

Question 2

A 50.0 g sample of water is heated from 22.0°C to 28.8°C. Given the specific heat of water is $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}$$, how much heat was absorbed by the water?

Accepted Answer

$$1.42 	imes 10^3$\ \mathrm{J}$$

Question 3

Which of the following statements about exothermic and endothermic reactions is correct?

Accepted Answer

Exothermic reactions release heat to the surroundings.

Question 4

A metal block with a mass of 55 g at 99.9°C is placed in 250 g of water at 25°C. At equilibrium, both are at 23°C. What is the specific heat of the metal? (Assume the specific heat of water is $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}.)$$

Accepted Answer

$$0.13\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}$$

Question 5

Which equation correctly expresses the First Law of Thermodynamics for a system?

Accepted Answer

$$\Delta U = q + w$$

Question 6

A gas absorbs 25 J of heat and does 243 J of work on the surroundings. What is the change in internal energy ($$\Delta U) of $$the gas?

Accepted Answer

$$-218\ \mathrm{J}$$

Question 7

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

Question 8

The standard enthalpy of formation ($$\Delta H_f^\circ) of a $$pure element in its reference form is:

Accepted Answer

$$0\ \mathrm{kJ\ $$mol^{-1}$$}$$

Question 9

Which calorimeter is best suited for measuring the heat of combustion of a fuel?

Accepted Answer

Bomb calorimeter

Question 10

If the enthalpy change for a reaction is $$-566\ \mathrm{kJ\ $$mol^{-1}$$}$$, what does the negative sign indicate?

Accepted Answer

The reaction is exothermic.

Question 11

A 100.0 g sample of water is heated from 21.0°C to 37.0°C. How much heat is required? (Specific heat of water = $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$})$$

Accepted Answer

$$6.69 	imes 10^3$\ \mathrm{J}$$

Question 12

Which of the following best describes the energy change when a chemical bond is formed?

Accepted Answer

Energy is released.

Question 13

Which of the following is NOT a type of molecular motion?

Accepted Answer

Ionic

Question 14

A reaction occurs in two steps with enthalpy changes $$\Delta H_1$ and $$\Delta $$H_2. $$According to Hess's Law, the total enthalpy change is:

Accepted Answer

$$\Delta H_1$ + \Delta H_2$

Question 15

Which of the following real-life scenarios best illustrates the conversion of potential energy to kinetic energy?

Accepted Answer

A cyclist coasting down a hill after reaching the top.

Question 16

Which of the following statements about specific heat is correct?

Accepted Answer

Specific heat is the amount of heat required to raise the temperature of 1 g of a substance by 1 K.

Question 17

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

Accepted Answer

The reaction is exothermic.

Question 18

Which of the following best describes the work done when a gas expands against a constant external pressure?

Accepted Answer

Work is done by the system on the surroundings.

Question 19

If 1.00 kg of sucrose ($$C_{12}H$$_{22}$$O_{11}) is $$completely combusted and $$\Delta H = -5.65 	imes 10^3$\ \mathrm{kJ\ $$mol^{-1}$$}$$, how much heat is released? (Molar mass of sucrose = $$342.3\ \mathrm{g\ $$mol^{-1}$$}$)

Accepted Answer

$$-1.65 	imes 10^4$\ \mathrm{kJ}$$

Thermochemistry: Energy, Heat, and Work in Chemical Systems

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