Q: Which of the following would have the smallest temperature change upon absorbing $$50\ \text{kJ} of $$heat? (Assume equal masses.)

Tin ($$0.227\ \text{J/g} \cdot ^\circ\text{C})$$

Q: Which of the following is a correct conversion between energy units?

$$1\ \text{kcal} = 1000\ \text{cal}$$

Q: A $$50.0\ \text{g}$$ sample of metal absorbs $$325\ \text{J} of $$heat, causing its temperature to rise from $$22.0^\circ\text{C} to$$ $$37.0^\circ\text{C}. $$What is the specific heat capacity of the metal?

$$0.433\ \text{J/g} \cdot ^\circ\text{C}$$

Question 1

A roller coaster at the top of its track (as shown in the first image) primarily possesses which type of energy, and what happens to this energy as the coaster descends?

Accepted Answer

Potential energy, which is converted to kinetic energy as it descends.

Question 2

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

Accepted Answer

Energy can be transferred or transformed, but the total energy remains constant.

Question 3

A chemical reaction releases 875 cal of heat. How many kilojoules (kJ) is this?

Accepted Answer

$$3.66\ 	ext{kJ}$$

Question 4

Which of the following scenarios represents an exothermic process?

Accepted Answer

Condensation of water vapor on a cold surface.

Question 5

Given the reaction: $$2\ 	ext{H}_2 (g) + 	ext{O}_2 (g) ightarrow 2\ 	ext{H}_2	ext{O} (l)\ \Delta H = -571.6\ 	ext{kJ}$$, how much heat is released when $$4.50\ 	ext{g} of $$hydrogen gas reacts completely?

Accepted Answer

$$-64.0\ 	ext{kJ}$$

Question 6

A system absorbs $$425\ 	ext{kJ} of $$heat and performs $$85\ 	ext{kJ} of $$work on the surroundings. What is the change in internal energy $$(\Delta E) of $$the system?

Accepted Answer

$$340\ 	ext{kJ}$$

Question 7

Which of the following would have the smallest temperature change upon absorbing $$50\ 	ext{kJ} of $$heat? (Assume equal masses.)

Accepted Answer

Tin ($$0.227\ 	ext{J/g} \cdot ^\circ	ext{C})$$

Question 8

A water treatment facility must raise the temperature of $$2245\ 	ext{g} of $$water from $$18.0^\circ	ext{C} to$$ $$26.0^\circ	ext{C}. $$The specific heat capacity of water is $$4.18\ 	ext{J/g} \cdot ^\circ	ext{C}. $$How much heat is required, in kilojoules?

Accepted Answer

$$75.0\ 	ext{kJ}$$

Question 9

Which of the following best describes what happens during the flat (plateau) regions of a heating curve?

Accepted Answer

Potential energy increases as a phase change occurs.

Question 10

Which of the following statements about enthalpy $$(\Delta H) is $$correct?

Accepted Answer

Enthalpy change equals the heat absorbed or released at constant pressure.

Question 11

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

Accepted Answer

Melting of ice in a drink.

Question 12

Which of the following correctly shows the energy flow for an exothermic system?

Accepted Answer

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

Question 13

A system releases $$155\ 	ext{kJ} of $$heat and receives $$22\ 	ext{kJ} of $$work from the surroundings. What is $$\Delta E$$ for the surroundings?

Accepted Answer

$$+133\ 	ext{kJ}$$

Question 14

Which of the following best describes Hess’s Law?

Accepted Answer

The total enthalpy change for a reaction is the same, regardless of the number of steps.

Question 15

Which of the following is a correct conversion between energy units?

Accepted Answer

$$1\ 	ext{kcal} = 1000\ 	ext{cal}$$

Question 16

A $$50.0\ 	ext{g}$$ sample of metal absorbs $$325\ 	ext{J} of $$heat, causing its temperature to rise from $$22.0^\circ	ext{C} to$$ $$37.0^\circ	ext{C}. $$What is the specific heat capacity of the metal?

Accepted Answer

$$0.433\ 	ext{J/g} \cdot ^\circ	ext{C}$$

Question 17

Which of the following best describes the energy changes when a weightlifter (as shown in the fourth image) lifts a barbell from the ground to above their head?

Accepted Answer

Chemical energy from the body is converted to potential energy of the barbell.

Question 18

Which of the following statements is TRUE regarding thermal equilibrium (as shown in the third image)?

Accepted Answer

Heat flows from the hotter object to the cooler object until both reach the same temperature.

Question 19

Which of the following processes is exothermic?

Accepted Answer

Condensation of water vapor.

Thermochemistry: Energy, Heat, and Enthalpy in Chemical Processes

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