Q: Which formula is used to calculate the heat required to raise the temperature of a substance using its specific heat capacity?

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

Q: A 500.0 g block of iron ($$C_s = 0.451 \text{ J g}^{-1} \text{C}^{-1}) is $$heated from $$22^\circC to$$ $$55^\circC. $$How much heat is absorbed?

$$q = 500.0 \times 0.451 \times (55 - 22) = 7,451 \text{ J}$$

Q: In bomb calorimetry, which equation is used to calculate the heat of reaction?

$$q = C_{cal} \times \Delta T$$

Q: A 250.0 g aluminum block ($$C_s = 0.902 \text{ J g}^{-1} \text{C}^{-1}) $$loses 24.3 kJ of energy. If its initial temperature is $$125.0^\circC$$, what is its final temperature?

$$T_{final} = 125.0 - \frac{24,300}{250.0 \times 0.902} = 16^\circC$$

Question 1

Which of the following statements correctly describes an endothermic process?

Accepted Answer

Heat is absorbed by the system from the surroundings, resulting in $$q \u003e 0.$$

Question 2

At constant pressure, which equation correctly relates enthalpy change ($$\Delta H) to $$heat?

Accepted Answer

$$\Delta H = q_p$$

Question 3

A chemical reaction occurs in a coffee-cup calorimeter at constant pressure. The temperature of the solution increases. Which of the following is true?

Accepted Answer

The reaction is exothermic and $$\Delta H \u003c 0.$$

Question 4

Which formula is used to calculate the heat required to raise the temperature of a substance using its specific heat capacity?

Accepted Answer

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

Question 5

A 500.0 g block of iron ($$C_s = 0.451 	ext{ J g}^{-1} 	ext{C}^{-1}) is $$heated from $$22^\circC to$$ $$55^\circC. $$How much heat is absorbed?

Accepted Answer

$$q = 500.0 	imes 0.451 	imes (55 - 22) = 7,451 	ext{ J}$$

Question 6

Which statement about enthalpy ($$\Delta H) is $$correct?

Accepted Answer

$$\Delta H is $$the sum of the system's internal energy and the product of its pressure and volume.

Question 7

For the reaction $$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$, $$\Delta H = -890 kJ. $$What does the negative sign indicate?

Accepted Answer

The reaction is exothermic and releases 890 kJ of heat.

Question 8

Which of the following best describes a thermodynamically favored (spontaneous) process?

Accepted Answer

A process that occurs without outside intervention, regardless of speed.

Question 9

In bomb calorimetry, which equation is used to calculate the heat of reaction?

Accepted Answer

$$q = C_{cal} 	imes \Delta T$$

Question 10

A 250.0 g aluminum block ($$C_s = 0.902 	ext{ J g}^{-1} 	ext{C}^{-1}) $$loses 24.3 kJ of energy. If its initial temperature is $$125.0^\circC$$, what is its final temperature?

Accepted Answer

$$T_{final} = 125.0 - \frac{24,300}{250.0 	imes 0.902} = 16^\circC$$

Question 11

Which of the following statements about heat capacity is true?

Accepted Answer

Specific heat capacity is the heat needed to raise 1 g of a substance by 1 K.

Question 12

Which equation correctly expresses the relationship between enthalpy change and internal energy change at constant pressure?

Accepted Answer

$$\Delta H = \Delta U + P\Delta V$$

Question 13

If the enthalpy of products is less than the enthalpy of reactants, what can be concluded about the reaction?

Accepted Answer

The reaction is exothermic and $$\Delta H \u003c 0.$$

Question 14

Which of the following is a correct application of calorimetry in a real-world scenario?

Accepted Answer

Measuring the heat released during the neutralization of an acid and a base in a coffee-cup calorimeter.

Question 15

Which of the following best explains why $$\Delta H is $$preferred over $$\Delta U$$ for reactions at constant pressure?

Accepted Answer

$$\Delta H$$ equals the heat transferred at constant pressure, which is easier to measure experimentally.

Question 16

Which of the following is true about the spontaneity of a process?

Accepted Answer

A spontaneous process can be either fast or slow.

Question 17

If 2.25 g of methane ($$\mathrm{CH_4$}) is $$burned at constant pressure, and $$\Delta H = -890 kJ $$for the reaction $$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$, how much heat is released?

Accepted Answer

$$q = \frac{2.25}{16.04} 	imes (-890) = -125 kJ$$

Question 18

Which of the following is NOT a factor that affects the value of $$\Delta H$$ for a reaction?

Accepted Answer

The color of the reactants.

Thermochemistry: Enthalpy, Calorimetry, and Heat Capacity

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