Q: A student wants to determine the enthalpy change for a reaction using a coffee-cup calorimeter. Which equation should they use to calculate the heat absorbed or released by the solution?

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

Q: In a bomb calorimeter, the heat of reaction is calculated using which of the following equations?

$$q_{rxn} = -C_{cal} \times \Delta T$$

Q: A 100.0 g sample of water is heated from 20.0 $$^\circC to 30.0$$ $$^\circC. $$How much energy is absorbed? (Specific heat of water = 4.18 J/g·K)

$$q = 100.0 \times 4.18 \times 10.0 = 4180 J$$

Q: Given the reaction: AgNO$$_3(aq) + $$HCl(aq) $$\rightarrow$$ AgCl(s) + HNO$$_3(aq$$), 100.0 g of solution (specific heat 4.18 J/g·$$^\circC) $$increases from 22.30 $$^\circC to 23.11$$ $$^\circC. $$What is the heat change $$q$$ for the solution?

$$q = 100.0 \times 4.18 \times (23.11 - 22.30) = 338 J$$

Q: A reaction in a bomb calorimeter causes the temperature of the water to increase by 2.50 K. If the heat capacity of the calorimeter is 3.00 kJ/K, what is the heat of reaction?

$$q_{rxn} = -3.00 \times 2.50 = -7.50 kJ$$

Question 1

Which of the following best describes the difference between heat capacity and specific heat capacity?

Accepted Answer

Heat capacity is the amount of energy required to raise the temperature of a substance by 1 K, usually for one mole, while specific heat capacity is for 1 g.

Question 2

A student wants to determine the enthalpy change for a reaction using a coffee-cup calorimeter. Which equation should they use to calculate the heat absorbed or released by the solution?

Accepted Answer

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

Question 3

Which of the following substances would require the most energy to raise the temperature of 10.0 g by 5.0 K, based on the table provided?

Accepted Answer

H$$_2O(l)$$

Question 4

In a bomb calorimeter, the heat of reaction is calculated using which of the following equations?

Accepted Answer

$$q_{rxn} = -C_{cal} 	imes \Delta T$$

Question 5

A 100.0 g sample of water is heated from 20.0 $$^\circC to 30.0$$ $$^\circC. $$How much energy is absorbed? (Specific heat of water = 4.18 J/g·K)

Accepted Answer

$$q = 100.0 	imes 4.18 	imes 10.0 = 4180 J$$

Question 6

Why is it important to know the heat capacity of the calorimeter before running a reaction in calorimetry experiments?

Accepted Answer

To accurately account for the heat absorbed or released by the calorimeter itself.

Question 7

Given the reaction: AgNO$$_3(aq) + $$HCl(aq) $$\rightarrow$$ AgCl(s) + HNO$$_3(aq$$), 100.0 g of solution (specific heat 4.18 J/g·$$^\circC) $$increases from 22.30 $$^\circC to 23.11$$ $$^\circC. $$What is the heat change $$q$$ for the solution?

Accepted Answer

$$q = 100.0 	imes 4.18 	imes (23.11 - 22.30) = 338 J$$

Question 8

Which of the following statements about enthalpy ($$\Delta H) is $$correct?

Accepted Answer

$$\Delta H is $$the difference between the final and initial enthalpy of a system.

Question 9

A reaction in a bomb calorimeter causes the temperature of the water to increase by 2.50 K. If the heat capacity of the calorimeter is 3.00 kJ/K, what is the heat of reaction?

Accepted Answer

$$q_{rxn} = -3.00 	imes 2.50 = -7.50 kJ$$

Question 10

Which scenario best illustrates the application of calorimetry in a real-world context?

Accepted Answer

Measuring the energy released when gasoline combusts in an engine.

Question 11

If 50.0 g of aluminum (specific heat 0.90 J/g·K) at 100.0 $$^\circC is $$placed in 100.0 g of water at 25.0 $$^\circC$$, what is the direction of heat flow?

Accepted Answer

Heat flows from aluminum to water.

Question 12

Which of the following is NOT a variable needed to calculate the heat transferred in a calorimetry experiment using $$q = m 	imes C_s 	imes \Delta T$$?

Accepted Answer

Volume of the calorimeter

Question 13

Why can't instantaneous enthalpies be determined directly in chemical reactions?

Accepted Answer

Because only enthalpy changes ($$\Delta H) $$can be measured, not absolute values.

Question 14

Which of the following would increase the accuracy of a calorimetry experiment?

Accepted Answer

Using a calorimeter with a known and calibrated heat capacity.

Question 15

A reaction is carried out in a coffee-cup calorimeter and the temperature of the solution decreases. What can you conclude about the reaction?

Accepted Answer

The reaction is endothermic.

Measuring Enthalpy: Calorimetry and Heat Capacity

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