Q: A 100 g sample of water is heated from 25°C to 75°C. If the specific heat capacity of water is $$4.18 \ \mathrm{J/g\cdot ^\circ C}$$, how much heat is absorbed by the water?

$$q = 100 \times 4.18 \times (75-25) = 20,900 \ \mathrm{J}$$

Q: Which equation correctly relates heat, specific heat, mass, and temperature change?

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

Question 1

Which of the following best describes the First Law of Thermodynamics?

Accepted Answer

Energy can neither be created nor destroyed, only transformed from one form to another.

Question 2

A 100 g sample of water is heated from 25°C to 75°C. If the specific heat capacity of water is $$4.18 \ \mathrm{J/g\cdot ^\circ C}$$, how much heat is absorbed by the water?

Accepted Answer

$$q = 100 	imes 4.18 	imes (75-25) = 20,900 \ \mathrm{J}$$

Question 3

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

Question 4

Which process is exothermic?

Accepted Answer

Condensation of steam

Question 5

Given the reaction: $$\mathrm{C_3H_8 (g) + 5 O_2$ (g) \rightarrow 3 CO_2$ (g) + 4 H_2O (g)}$$ $$\Delta H = -2220 \ \mathrm{kJ}$$, how much heat is released when 44 g of $$\mathrm{CO_2$} is $$produced? (Molar mass $$\mathrm{CO_2$} = 44 \ \mathrm{g/mol})$$

Accepted Answer

$$-740 \ \mathrm{kJ}$$

Question 6

Which of the following best explains why water has a high specific heat capacity?

Accepted Answer

Water has strong hydrogen bonds that require more energy to break.

Question 7

A chemical cold pack contains ammonium nitrate ($$\mathrm{NH_4NO_3}) $$and water. When activated, the pack becomes cold to the touch. Which statement is correct?

Accepted Answer

The dissolution of $$\mathrm{NH_4NO_3} is $$endothermic and $$\Delta H is $$positive.

Question 8

Which equation correctly relates heat, specific heat, mass, and temperature change?

Accepted Answer

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

Question 9

Which of the following statements about bond energies is correct?

Accepted Answer

Forming bonds releases energy.

Question 10

A reaction has $$\Delta H = +150 \ \mathrm{kJ}. $$Which of the following is true?

Accepted Answer

The reaction is endothermic and absorbs heat.

Question 11

Which of the following is NOT a state function?

Accepted Answer

Heat ($$q)$$

Question 12

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 13

A calorimeter is used to measure:

Accepted Answer

The change in temperature of a reaction.

Question 14

Which of the following best describes an exothermic reaction?

Accepted Answer

The system releases heat to the surroundings.

Question 15

Which of the following is true about the standard enthalpy of formation ($$\Delta H_f^\circ) $$for an element in its standard state?

Accepted Answer

$$\Delta H_f^\circ is $$zero.

Question 16

Which of the following best describes the energy changes during the combustion of propane in a barbecue grill?

Accepted Answer

Potential energy in propane is converted to heat and light.

Question 17

If 250 mL of 1.0 M NaOH is mixed with 250 mL of 1.0 M HCl and the temperature increases, what can you conclude about the reaction?

Accepted Answer

It is exothermic and $$\Delta H is $$negative.

Question 18

Which of the following equations is used to estimate the enthalpy change of a reaction using bond dissociation energies?

Accepted Answer

$$\Delta H = D(	ext{Reactant bonds}) - D(	ext{Product bonds})$$

Question 19

Which of the following is an example of potential energy?

Accepted Answer

A stretched rubber band

Question 20

Which of the following best describes the energy change when ice melts?

Accepted Answer

Energy is absorbed and the process is endothermic.

Thermochemistry: Energy, Enthalpy, and Calorimetry

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