Q: Which of the following equations correctly calculates the amount of heat ($$q) $$absorbed or released by a substance?

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

Question 1

Which of the following best describes the law of conservation of energy as it applies to a chemical reaction in a closed system?

Accepted Answer

The total energy of the system and surroundings remains constant; energy is only transferred or transformed.

Question 2

A 50.0 g block of metal at $$80.0\ ^\circ\mathrm{C} is $$placed in 100.0 g of water at $$25.0\ ^\circ\mathrm{C}. If $$the final temperature of the system is $$30.0\ ^\circ\mathrm{C}$$, and the specific heat capacity of water is $$4.18\ \mathrm{J/g\ ^\circ C}$$, what is the total heat lost by the metal?

Accepted Answer

$$-1045\ \mathrm{J}$$

Question 3

Which of the following is an example of potential energy being converted to kinetic energy?

Accepted Answer

A compressed spring being released and launching a ball.

Question 4

Which equation correctly relates the change in internal energy ($$\Delta E) of a $$system to heat ($$q) $$and work ($$w$$)?

Accepted Answer

$$\Delta E = q + w$$

Question 5

A student claims that the path taken to climb a mountain affects the change in potential energy. Which concept from thermochemistry refutes this claim?

Accepted Answer

The concept of state functions

Question 6

A chemical reaction in a hand warmer releases heat to your hands. Which of the following statements is true regarding the energy changes?

Accepted Answer

The system (hand warmer) loses energy and the surroundings (your hands) gain the same amount of energy.

Question 7

Which of the following best defines specific heat capacity ($$C_s$$)?

Accepted Answer

The amount of heat required to raise the temperature of one gram of a substance by $$1\ ^\circ\mathrm{C}.$$

Question 8

A 25.0 g copper penny (specific heat $$C_s = 0.385\ \mathrm{J/g\ ^\circ C}) is $$heated from $$-8.0\ ^\circ\mathrm{C} to$$ $$37.0\ ^\circ\mathrm{C}. $$How much heat is absorbed by the penny?

Accepted Answer

$$434\ \mathrm{J}$$

Question 9

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 10

If a reaction absorbs energy from the surroundings, which of the following is true?

Accepted Answer

$$\Delta E_{system} \u003e 0$$

Question 11

A 100.0 g sample of water at $$90.0\ ^\circ\mathrm{C} is $$mixed with 100.0 g of water at $$10.0\ ^\circ\mathrm{C}. $$What is the final temperature, assuming no heat is lost to the surroundings? ($$C_s$$ for water = $$4.18\ \mathrm{J/g\ ^\circ C})$$

Accepted Answer

$$50.0\ ^\circ\mathrm{C}$$

Question 12

Which of the following best describes the difference between heat and temperature?

Accepted Answer

Temperature is a measure of the average kinetic energy of particles, while heat is energy transferred due to a temperature difference.

Question 13

Which of the following equations correctly calculates the amount of heat ($$q) $$absorbed or released by a substance?

Accepted Answer

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

Question 14

A 10.0 g piece of metal at $$100.0\ ^\circ\mathrm{C} is $$placed in 50.0 g of water at $$25.0\ ^\circ\mathrm{C}. $$The final temperature is $$27.0\ ^\circ\mathrm{C}. If $$the specific heat of water is $$4.18\ \mathrm{J/g\ ^\circ C}$$, what is the specific heat of the metal?

Accepted Answer

$$0.12\ \mathrm{J/g\ ^\circ C}$$

Question 15

Which of the following statements about exothermic and endothermic reactions is correct?

Accepted Answer

Exothermic reactions result in a decrease in the internal energy of the system.

Question 16

Which of the following is the correct SI unit for energy?

Accepted Answer

Joule

Question 17

A 200.0 g rock is heated from $$20.0\ ^\circ\mathrm{C} to$$ $$50.0\ ^\circ\mathrm{C} by $$absorbing $$1,500\ \mathrm{J} of $$heat. What is the specific heat capacity of the rock?

Accepted Answer

$$0.25\ \mathrm{J/g\ ^\circ C}$$

Question 18

Which of the following best describes the energy transfer when you hold a hot cup of coffee?

Accepted Answer

Energy flows from the hot cup to your cooler hand as heat.

Question 19

Which of the following is a correct conversion factor between calories and joules?

Accepted Answer

$$1\ \mathrm{cal} = 4.184\ \mathrm{J}$$

Thermochemistry: Energy, Heat, and Work in Chemical Systems

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