Q: A 95.4-g piece of copper increases in temperature from 25.0°C to 48.0°C when it absorbs 849 J of heat. What is the specific heat of copper?

$$C = \frac{849\ \mathrm{J}}{95.4\ \mathrm{g} \times 23.0$$^{\circ}$$C} = 0.387\ \mathrm{J/(g\cdot{}^{\circ}C)}$$

Q: Which of the following equations correctly expresses the relationship for calculating specific heat?

$$C = \frac{q}{m \times \Delta T}$$

Question 1

Which of the following best describes the law of conservation of energy as it applies to chemical reactions?

Accepted Answer

Energy is neither created nor destroyed during a chemical reaction; it is only transferred or transformed.

Question 2

A sample of ethanol absorbs 676 J of heat, causing its temperature to rise from 22°C to 64°C. If the specific heat of ethanol is $$2.4\ \mathrm{J/(g\cdot{}^{\circ}C)}$$, what is the mass of the ethanol sample?

Accepted Answer

$$m = \frac{676\ \mathrm{J}}{2.4\ \mathrm{J/(g\cdot{}^{\circ}C)} 	imes (64-22$$)^{\circ}$$C} = 6.7\ \mathrm{g}$$

Question 3

Which of the following statements about specific heat is correct?

Accepted Answer

Specific heat is the amount of heat needed to raise the temperature of 1 g of a substance by 1°C.

Question 4

When a piece of wood is burned, the energy released comes from:

Accepted Answer

Chemical potential energy stored in the wood's bonds.

Question 5

Which of the following is an example of an endothermic process?

Accepted Answer

Dissolving ammonium nitrate in water in a cold pack.

Question 6

A 95.4-g piece of copper increases in temperature from 25.0°C to 48.0°C when it absorbs 849 J of heat. What is the specific heat of copper?

Accepted Answer

$$C = \frac{849\ \mathrm{J}}{95.4\ \mathrm{g} 	imes 23.0$$^{\circ}$$C} = 0.387\ \mathrm{J/(g\cdot{}^{\circ}C)}$$

Question 7

Why does lava cool more quickly in water than in air?

Accepted Answer

Water has a higher specific heat than air, so it absorbs more heat from the lava.

Question 8

Which of the following best describes an exothermic process?

Accepted Answer

A process that releases heat to the surroundings.

Question 9

If 1000 J of heat is transferred from a system to its surroundings, what is the sign of $$q$$ for the system?

Accepted Answer

$$q is $$negative.

Question 10

Which of the following equations correctly expresses the relationship for calculating specific heat?

Accepted Answer

$$C = \frac{q}{m 	imes \Delta T}$$

Question 11

A freshly baked apple pie has filling and crust at the same temperature. Why does the filling burn your tongue more easily than the crust?

Accepted Answer

The filling has a higher specific heat and releases more heat as it cools.

Question 12

Which of the following is NOT a correct unit for specific heat?

Accepted Answer

$$\mathrm{J$$/^{\circ}$$C}$$

Question 13

Which of the following statements about heat flow is correct?

Accepted Answer

Heat flows spontaneously from a warmer object to a cooler object.

Question 14

A cold pack used by athletes contains ammonium nitrate and water. When activated, the pack feels cold. What does this indicate about the process?

Accepted Answer

The process is endothermic; heat is absorbed from the surroundings.

Question 15

Which of the following factors does NOT affect the heat capacity of an object?

Accepted Answer

The color of the object.

Question 16

If the temperature of 50 g of water increases by 10°C after absorbing 2090 J of heat, what is the specific heat of water?

Accepted Answer

$$C = \frac{2090\ \mathrm{J}}{50\ \mathrm{g} 	imes 10$$^{\circ}$$C} = 4.18\ \mathrm{J/(g\cdot{}^{\circ}C)}$$

Question 17

Which of the following best defines 'system' in thermochemistry?

Accepted Answer

The part of the universe on which you focus your attention.

Question 18

During the freezing of water into ice, which of the following statements is true?

Accepted Answer

Heat flows from the water into the air; the process is exothermic.

Thermochemistry: The Flow of Energy in Chemical Processes

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