Q: A foam cup calorimeter is used to measure the enthalpy change of a reaction in aqueous solution. Which equation correctly relates the heat absorbed or released by the surroundings to the mass, specific heat, and temperature change of water?

$$q_{surr} = m \times C \times \Delta T$$

Q: A bomb calorimeter is used to measure the heat released when a match burns. Which equation would you use to calculate the heat released, given the mass, specific heat, and temperature change of the water?

$$q = -m \times C \times \Delta T$$

Q: Which equation represents the heat of combustion for methane at standard conditions?

$$\text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(l) + 890 \text{ kJ}$$

Q: Which formula would you use to calculate the enthalpy change for a reaction in a constant-pressure calorimeter?

$$\Delta H = -m \times C \times \Delta T$$

Q: Which of the following is a thermochemical equation?

$$\text{CaO}(s) + \text{H}_2\text{O}(l) \rightarrow \text{Ca(OH)}_2(s) + 65.2 \text{ kJ}$$

Question 1

Which device is used to measure the absorption or release of heat in chemical or physical processes, and what is its primary function?

Accepted Answer

Calorimeter; measures the heat flow into or out of a system.

Question 2

A foam cup calorimeter is used to measure the enthalpy change of a reaction in aqueous solution. Which equation correctly relates the heat absorbed or released by the surroundings to the mass, specific heat, and temperature change of water?

Accepted Answer

$$q_{surr} = m 	imes C 	imes \Delta T$$

Question 3

In a constant-pressure calorimeter, the enthalpy change for a reaction is calculated as $$\Delta H = -m 	imes C 	imes \Delta T. If $$the temperature of the solution increases, what does this indicate about the reaction?

Accepted Answer

The reaction is exothermic and $$\Delta H is $$negative.

Question 4

A bomb calorimeter is used to measure the heat released when a match burns. Which equation would you use to calculate the heat released, given the mass, specific heat, and temperature change of the water?

Accepted Answer

$$q = -m 	imes C 	imes \Delta T$$

Question 5

A reaction in a constant-pressure calorimeter causes the temperature of 367 g of water to rise from 24°C to 87°C. The specific heat of water is 4.18 J/(g·°C). What is the enthalpy change for the reaction?

Accepted Answer

$$\Delta H = -97 	ext{ kJ}$$

Question 6

Which of the following best describes an endothermic reaction in a thermochemical equation?

Accepted Answer

The enthalpy change is written as a reactant and is positive.

Question 7

The decomposition of 2 mol of sodium bicarbonate requires 85 kJ of heat. How much heat is required to decompose 4 mol of sodium bicarbonate?

Accepted Answer

170 kJ

Question 8

Why must the physical state of reactants and products be specified in thermochemical equations?

Accepted Answer

Because the enthalpy change depends on the physical state of the substances involved.

Question 9

Which equation represents the heat of combustion for methane at standard conditions?

Accepted Answer

$$	ext{CH}_4(g) + 2	ext{O}_2(g) ightarrow 	ext{CO}_2(g) + 2	ext{H}_2	ext{O}(l) + 890 	ext{ kJ}$$

Question 10

A student mixes 25.0 mL of water containing 0.025 mol HCl at 25.0°C with 25.0 mL of water containing 0.025 mol NaOH at 25.0°C in a foam-cup calorimeter. The final temperature is 32.0°C. What is the enthalpy change for the reaction?

Accepted Answer

$$\Delta H = -1.5 	ext{ kJ}$$

Question 11

Which of the following statements about calorimetry is correct?

Accepted Answer

In an endothermic process, the heat absorbed by the system is equal to the heat released by its surroundings.

Question 12

Which formula would you use to calculate the enthalpy change for a reaction in a constant-pressure calorimeter?

Accepted Answer

$$\Delta H = -m 	imes C 	imes \Delta T$$

Question 13

Which of the following is a thermochemical equation?

Accepted Answer

$$	ext{CaO}(s) + 	ext{H}_2	ext{O}(l) ightarrow 	ext{Ca(OH)}_2(s) + 65.2 	ext{ kJ}$$

Question 14

If the decomposition of 2 mol NaHCO3(s) absorbs 85 kJ, how much heat is absorbed when 2.24 mol NaHCO3(s) decomposes?

Accepted Answer

95 kJ

Question 15

Which of the following best describes the heat of combustion?

Accepted Answer

The heat of reaction for the complete burning of one mole of a substance.

Question 16

Which equation would you use to convert the heat calculated in joules to kilojoules?

Accepted Answer

$$1 	ext{ kJ} = 1000 	ext{ J}$$

Measuring and Expressing Enthalpy Changes (Thermochemistry)

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