Q: A 37.5 g sample of water is cooled from 42.0°C to 7.0°C. Given the molar heat capacity of water is $$C_p = 75.3 \mathrm{J}/\mathrm{mol}^\circ\mathrm{C}$$ and the molar mass of water is $$18.0 \mathrm{g}/\mathrm{mol}$$, what is the value of $$q$$ for the water?

$$q = -5.49 \times 10^3$ \mathrm{J}$$

Q: Calculate the enthalpy change when 240 g of ice melts at 0°C. The molar enthalpy of fusion for water is $$\Delta H_{fus} = 6009.5 \mathrm{J}/\mathrm{mol}$$ and the molar mass of water is $$18.0 \mathrm{g}/\mathrm{mol}.$$

$$\Delta H = 8.01 \times 10^4$ \mathrm{J}$$

Question 1

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

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 2

A 24.0-g aluminum can is heated, raising its temperature by 15.0°C. Given the specific heat of aluminum is $$c = 0.900 \mathrm{J}/\mathrm{g}^\circ\mathrm{C}$$, what is the amount of heat absorbed by the can?

Accepted Answer

$$q = 324 \mathrm{J}$$

Question 3

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 4

A gas absorbs 515 J of heat and does 218 J of work on its surroundings. What is the change in internal energy of the system?

Accepted Answer

$$\Delta E = 297 \mathrm{J}$$

Question 5

Which of the following is an example of potential energy in a chemical context?

Accepted Answer

The energy stored in the bonds of glucose molecules.

Question 6

A 37.5 g sample of water is cooled from 42.0°C to 7.0°C. Given the molar heat capacity of water is $$C_p = 75.3 \mathrm{J}/\mathrm{mol}^\circ\mathrm{C}$$ and the molar mass of water is $$18.0 \mathrm{g}/\mathrm{mol}$$, what is the value of $$q$$ for the water?

Accepted Answer

$$q = -5.49 	imes 10^3$ \mathrm{J}$$

Question 7

Which statement about enthalpy ($$\Delta H) is $$correct for a process occurring at constant pressure?

Accepted Answer

$$\Delta H$$ equals the heat exchanged with the surroundings at constant pressure.

Question 8

Calculate the enthalpy change when 240 g of ice melts at 0°C. The molar enthalpy of fusion for water is $$\Delta H_{fus} = 6009.5 \mathrm{J}/\mathrm{mol}$$ and the molar mass of water is $$18.0 \mathrm{g}/\mathrm{mol}.$$

Accepted Answer

$$\Delta H = 8.01 	imes 10^4$ \mathrm{J}$$

Question 9

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction in which $$\Delta H is $$negative and heat is released.

Question 10

Which of the following is NOT a factor that makes petroleum a preferred fuel for transportation?

Accepted Answer

It is highly explosive under normal conditions.

Question 11

A calorimeter is calibrated by supplying 100.0 J of heat, resulting in a temperature increase of 0.850°C. What is the calorimeter constant?

Accepted Answer

$$C_{calorimeter} = 118 \mathrm{J}/^\circ\mathrm{C}$$

Question 12

Which of the following is a correct application of Hess's Law?

Accepted Answer

The enthalpy change of a reaction is the sum of the enthalpy changes of its individual steps.

Question 13

Which battery type is rechargeable and has high energy density, making it suitable for modern electronics?

Accepted Answer

Lithium-ion

Question 14

During the Three Mile Island accident, melted UO$$_2$$ fuel pellets fell into water. To determine the mass of fuel that melted, which information is NOT required?

Accepted Answer

The atomic number of uranium

Question 15

Which formula is used to calculate the amount of heat required to raise the temperature of a substance?

Accepted Answer

$$q = m c \Delta T$$

Question 16

A chemical reaction releases 180.5 kJ of heat for every 2 mol of NO produced. How much heat is absorbed when 15.7 g of NO is generated? (Molar mass of NO = 30.0 g/mol)

Accepted Answer

$$q = 47.2 \mathrm{kJ}$$

Question 17

Which of the following statements about energy conversion devices is correct?

Accepted Answer

A solar cell converts solar energy to electrical energy with less than 20% efficiency.

Question 18

Which of the following is the correct definition of specific heat capacity?

Accepted Answer

The amount of heat required to raise the temperature of one gram of a substance by 1 K.

Energy and Chemistry: Thermochemistry and Energy Transformations

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