Question 1

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

Accepted Answer

Heat is the flow of energy due to a temperature difference, while temperature is a measure of the average kinetic energy of particles.

Question 2

A student dissolves 5.00 g of MgSO$$_4 in 100.0 g of $$water in a calorimeter. The temperature of the water increases from 22.0$$^\circC to 27.0$^\circC. If $$the specific heat capacity of water is $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}$$, what is the approximate enthalpy change ($$\Delta H) $$for the dissolution of MgSO$$_4$$ per mole? (Molar mass of MgSO$$_4 = 120.4 g/$$mol)

Accepted Answer

$$-41.8\ \mathrm{kJ\ $$mol^{-1}$$}$$

Question 3

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

Accepted Answer

$$\Delta H is $$negative for exothermic reactions and positive for endothermic reactions.

Question 4

In a calorimetry experiment, a student mixes 50.0 mL of 1.0 M HCl with 50.0 mL of 1.0 M NaOH. The temperature rises by 6.0$$^\circC. $$Assuming the density and specific heat of the solution are the same as water, what is the heat released ($$q) in $$the reaction? (Specific heat of water = $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}$$; density = $$1.00\ \mathrm{g\ mL$$^{-1}$$})$$

Accepted Answer

$$2.51\ \mathrm{kJ}$$

Question 5

Which of the following best explains why a cold pack feels cold when activated?

Accepted Answer

The dissolution process is endothermic, absorbing heat from your skin.

Question 6

Consider the reaction: $$\mathrm{C_6H_{12}O_6$} + 6\mathrm{O_2$} \rightarrow 6\mathrm{CO_2$} + 6\mathrm{H_2O}. $$When this reaction occurs in a test tube with KClO$$_3 as a $$catalyst, it produces a lilac flame and a broken test tube. When it occurs in the body, it powers ATP synthesis. What is true about the enthalpy change ($$\Delta H) $$for these two scenarios?

Accepted Answer

$$\Delta H is $$the same for both, but the energy is released differently.

Question 7

Which law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed?

Accepted Answer

First Law of Thermodynamics

Question 8

A chemical reaction has $$\Delta H = -100\ \mathrm{kJ\ $$mol^{-1}$$}$$ and $$\Delta S = -200\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$}. At $$what temperature (in K) does the reaction become non-spontaneous? (Use $$\Delta G = \Delta H - T\Delta S)$$

Accepted Answer

$$500\ \mathrm{K}$$

Question 9

Which of the following is NOT a mode of heat transfer?

Accepted Answer

Diffusion

Question 10

Which statement about entropy ($$\Delta S) is $$correct?

Accepted Answer

Entropy increases when a solid melts to a liquid.

Question 11

A handwarmer contains iron powder that reacts with oxygen to form iron(III) oxide. Which of the following best describes the thermodynamic nature of this process?

Accepted Answer

It is exothermic and increases entropy.

Question 12

Which of the following best describes the use of Hess's Law in thermochemistry?

Accepted Answer

It allows calculation of the enthalpy change of a reaction by combining known enthalpy changes of other reactions.

Question 13

A student is asked to predict which salt, MgSO$$_4 or $$MgSO$$_4 \cdot 7H$_2O$$, will be more exothermic upon dissolving in water. Which reasoning is correct?

Accepted Answer

MgSO$$_4 is $$more exothermic because it is anhydrous and will hydrate upon dissolving, releasing more energy.

Question 14

Which of the following is a correct application of dimensional analysis in thermochemistry?

Accepted Answer

Converting $$\mathrm{J} to$$ $$\mathrm{kJ} by $$dividing by 1000.

Question 15

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

Accepted Answer

The entropy of the universe increases in any spontaneous process.

Question 16

A reaction has $$\Delta H = +50\ \mathrm{kJ\ $$mol^{-1}$$}$$ and $$\Delta S = +200\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$}. At $$what minimum temperature (in K) will the reaction become spontaneous?

Accepted Answer

$$250\ \mathrm{K}$$

Question 17

Which of the following is a real-life example of convection as a mode of heat transfer?

Accepted Answer

Warm air rising above a radiator and circulating in a room.

Question 18

Which of the following best explains why the enthalpy change for a reaction is the same whether it occurs in a test tube or in the human body?

Accepted Answer

Enthalpy is a state function and depends only on the initial and final states, not the pathway.

Question 19

Which of the following is the correct formula for calculating the heat absorbed or released in a calorimetry experiment?

Accepted Answer

$$q = m c \Delta T$$

Question 20

A process occurs with $$\Delta H = -20\ \mathrm{kJ}$$ and $$\Delta S = -50\ \mathrm{J\ K$$^{-1}$$}. At 298 K$$, what is the value of $$\Delta G$$? (Give your answer in kJ.)

Accepted Answer

$$-5.1\ \mathrm{kJ}$$

Calorimetry, Enthalpy, Entropy, and Gibbs Free Energy: Study Notes

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