Q: Which equation is used to calculate the heat required to raise the temperature of a substance, given its mass, specific heat, and temperature change?

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

Q: Which of the following is the correct formula for calculating the standard enthalpy change of a reaction using standard enthalpies of formation?

$$\Delta H^\circ_{rxn} = \Sigma n \Delta H^\circ_f (\text{products}) - \Sigma m \Delta H^\circ_f (\text{reactants})$$

Question 1

Which of the following best describes the energy transformation occurring when a piece of wood is burned in a grill, as shown in the first image?

Accepted Answer

Chemical potential energy in the wood is converted to heat and light energy.

Question 2

A champagne bottle is opened and the cork pops out rapidly, as shown in the second image. Which type of energy is primarily responsible for this phenomenon?

Accepted Answer

Potential energy stored in the compressed gas inside the bottle.

Question 3

Which type of molecular motion is depicted in the third image (CO2 molecule spinning around its axis)?

Accepted Answer

Rotational motion

Question 4

The fourth image shows a CO2 molecule moving in a straight line. What type of kinetic energy is this?

Accepted Answer

Translational kinetic energy

Question 5

Which of the following statements about temperature and thermal energy is best illustrated by the image comparing a coffee cup and a bathtub, both at 90°C?

Accepted Answer

The bathtub has more thermal energy because it contains more water.

Question 6

Which system is best described as an open system based on the images provided?

Accepted Answer

A bottle with both heat and water vapor exchange

Question 7

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

Accepted Answer

$$\Delta U = q + w$$

Question 8

A reaction occurs in a closed cylinder with a movable piston. If the system does 200 J of work on the surroundings and absorbs 150 J of heat, what is $$\Delta U$$ for the system?

Accepted Answer

$$\Delta U = -50 J$$

Question 9

Which of the following is true for an exothermic reaction, as shown in the image with heat leaving the system?

Accepted Answer

$$\Delta H \u003c 0$$

Question 10

Which of the following best describes a state function?

Accepted Answer

A property that depends only on the initial and final states, not the path

Question 11

Which equation is used to calculate the heat required to raise the temperature of a substance, given its mass, specific heat, and temperature change?

Accepted Answer

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

Question 12

A 100 g sample of silver (specific heat $$C_s = 0.22 J g$^{-1} K$^{-1}) is $$heated with 88 J of energy. What is the temperature change ($$\Delta T$$)?

Accepted Answer

$$\Delta T = 0.4 K$$

Question 13

Which calorimeter is used to measure the heat of combustion at constant volume?

Accepted Answer

Bomb calorimeter

Question 14

Which of the following statements about Hess's Law is correct?

Accepted Answer

The enthalpy change for a reaction is the sum of the enthalpy changes for each step.

Question 15

Given the following reactions and enthalpy changes:
$$\mathrm{CH_4$(g) + 2O_2(g) \rightarrow CO_2$(g) + 2H_2O(l)}$$ $$\Delta H_1$ = -890 kJ$$
$$\mathrm{2CO(g) + O_2$(g) \rightarrow 2CO_2(g)}$$ $$\Delta H_2$ = -566 kJ
$$What is $$\Delta H$$ for $$\mathrm{2CH_4(g) + 3O_2(g) \rightarrow 2CO(g) + 4H_2O(l)}$$?

Accepted Answer

$$\Delta H = -1214 kJ$$

Question 16

Which of the following is the correct formula for calculating the standard enthalpy change of a reaction using standard enthalpies of formation?

Accepted Answer

$$\Delta H^\circ_{rxn} = \Sigma n \Delta H^\circ_f (	ext{products}) - \Sigma m \Delta H^\circ_f (	ext{reactants})$$

Question 17

Which of the following is NOT a state function?

Accepted Answer

Heat ($$q)$$

Question 18

A reaction in a bomb calorimeter causes the temperature of the calorimeter to rise by 2.5°C. If the heat capacity of the calorimeter is 5.0 kJ °C$$^{-1}$$, what is the heat released by the reaction?

Accepted Answer

12.5 kJ

Question 19

Which of the following best describes the difference between specific heat ($$C_s) $$and molar heat capacity ($$C_m$$)?

Accepted Answer

$$C_s is $$the heat required to raise the temperature of 1 g by 1 K, $$C_m is $$per mole.

Thermochemistry: Energy, Enthalpy, and Calorimetry

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