Q: A 50.0 g sample of copper ($$C_s = 0.385 \ J/g\cdot ^\circ C) is $$heated from $$20.0^\circ C to$$ $$80.0^\circ C. $$How much heat is absorbed by the copper?

$$q = 50.0 \times 0.385 \times (80.0 - 20.0) = 1155 \ J$$

Q: A 1.00 kg block of aluminum ($$C_s = 0.903 \ J/g\cdot ^\circ C) $$cools from $$35^\circ C to$$ $$20^\circ C. $$How much heat is released?

$$q = 1.00 \times 0.903 \times (20 - 35) = -13,550 \ J$$

Q: Which equation is used to calculate the heat required to change the temperature of a substance?

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

Question 1

Which statement best describes the First Law of Thermodynamics?

Accepted Answer

The total energy of the universe is constant; energy can be transferred between system and surroundings as heat and work.

Question 2

A 50.0 g sample of copper ($$C_s = 0.385 \ J/g\cdot ^\circ C) is $$heated from $$20.0^\circ C to$$ $$80.0^\circ C. $$How much heat is absorbed by the copper?

Accepted Answer

$$q = 50.0 	imes 0.385 	imes (80.0 - 20.0) = 1155 \ J$$

Question 3

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 4

A 32.5 g cube of aluminum ($$C_s = 0.903 \ J/g\cdot ^\circ C) at$$ $$45.8^\circ C is $$placed in 105.3 g of water ($$C_s = 4.18 \ J/g\cdot ^\circ C) at$$ $$15.4^\circ C. $$What is the final equilibrium temperature?

Accepted Answer

$$T_f = 17.3^\circ C$$

Question 5

Which equation correctly represents the relationship between heat lost and heat gained in a thermally isolated system?

Accepted Answer

$$q_{system} = -q_{surroundings}$$

Question 6

If a system absorbs 500 J of heat and does 200 J of work on the surroundings, what is the change in internal energy ($$\Delta E$$)?

Accepted Answer

$$\Delta E = 500 - 200 = 300 \ J$$

Question 7

Which of the following best describes an exothermic reaction?

Accepted Answer

The system releases heat to the surroundings.

Question 8

What is the specific heat capacity ($$C_s) of $$water?

Accepted Answer

$$C_s = 4.18 \ J/g\cdot ^\circ C$$

Question 9

A 1.00 kg block of aluminum ($$C_s = 0.903 \ J/g\cdot ^\circ C) $$cools from $$35^\circ C to$$ $$20^\circ C. $$How much heat is released?

Accepted Answer

$$q = 1.00 	imes 0.903 	imes (20 - 35) = -13,550 \ J$$

Question 10

Which of the following is NOT a form of energy described in thermochemistry?

Accepted Answer

Nuclear energy

Question 11

If the internal energy of a system decreases by 250 J, what is the sign of $$\Delta E$$?

Accepted Answer

$$\Delta E is $$negative

Question 12

Which equation is used to calculate the heat required to change the temperature of a substance?

Accepted Answer

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

Question 13

A chemical reaction occurs in a system and the surroundings lose 100 J of energy. What is the change in internal energy of the system?

Accepted Answer

$$\Delta E_{sys} = -\Delta E_{surr} = 100 \ J$$

Question 14

Which of the following statements about specific heat capacity is correct?

Accepted Answer

Specific heat capacity is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

Question 15

Which sign convention is correct for work done BY the system?

Accepted Answer

Work is negative

Question 16

A student mixes 50.0 g of sand ($$C_s = 0.84 \ J/g\cdot ^\circ C) at$$ $$30.0^\circ C$$ with 100.0 g of water ($$C_s = 4.18 \ J/g\cdot ^\circ C) at$$ $$20.0^\circ C. $$What is the final temperature after thermal equilibrium?

Accepted Answer

$$T_f = 22.7^\circ C$$

Question 17

Which formula is used to calculate the temperature change of a substance?

Accepted Answer

$$\Delta T = T_{final} - T_{initial}$$

Question 18

Which of the following is an example of potential energy?

Accepted Answer

A stretched spring

Question 19

Which equation represents the relationship between the internal energy change of a system and its surroundings?

Accepted Answer

$$\Delta E_{sys} = -\Delta E_{surr}$$

Thermochemistry: Energy, Heat, and Thermal Equilibrium

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