Q: 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 amount of heat released by the dissolution?

$$2.09 \times 10^3$\ \mathrm{J}$$

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 amount of heat released by the dissolution?

Accepted Answer

$$2.09 	imes 10^3$\ \mathrm{J}$$

Question 3

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

Accepted Answer

A negative $$\Delta H$$ indicates an exothermic reaction, where heat is released to the surroundings.

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 6.5$$^\circC. $$Assuming the density and specific heat of the solution are the same as water, what is the heat of neutralization per mole of water formed? (Assume $$c = 4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}$$ and $$1\ \mathrm{mL} = 1\ \mathrm{g})$$

Accepted Answer

$$-57\ \mathrm{kJ\ $$mol^{-1}$$}$$

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

Which of the following is the correct expression for Gibbs Free Energy?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 7

Consider the combustion of glucose: $$\mathrm{C_6H_{12}O_6$ + 6O_2 \rightarrow 6CO_2 + 6H_2O}. In $$the laboratory, this reaction produces a lilac flame and a broken test tube, while in the body it powers ATP synthesis. Which statement best explains the difference in energy transfer?

Accepted Answer

In the lab, energy is released as heat and light, while in the body, energy is transferred to ATP through a series of controlled steps.

Question 8

Which of the following is NOT a mode of heat transfer discussed in class?

Accepted Answer

Diffusion

Question 9

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

Accepted Answer

$$500\ \mathrm{K}$$

Question 10

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

Accepted Answer

Entropy is a measure of the disorder or randomness of a system.

Question 11

Which of the following best describes Hess’s Law?

Accepted Answer

The enthalpy change for a reaction is the same, regardless of the pathway taken.

Question 12

A hot pack contains a salt that, when dissolved in water, causes the temperature to rise. Which of the following is true about the dissolution process?

Accepted Answer

The process is exothermic, and $$\Delta H is $$negative.

Question 13

Which of the following best explains why MgSO$$_4 \cdot 7H$_2O is $$less exothermic upon dissolving in water than anhydrous MgSO$$_4$$?

Accepted Answer

MgSO$$_4 \cdot 7H$_2O is $$already hydrated, so less energy is released when it dissolves.

Question 14

Which of the following is a correct statement of the Second Law of Thermodynamics?

Accepted Answer

The total entropy of the universe increases in any spontaneous process.

Question 15

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

Accepted Answer

$$250\ \mathrm{K}$$

Question 16

Which of the following best describes the role of calorimetry in chemistry?

Accepted Answer

Calorimetry measures the heat exchanged during chemical or physical processes.

Question 17

Which of the following is an example of energy transfer by radiation?

Accepted Answer

The warmth you feel from sunlight on your skin.

Question 18

Which of the following is true about the spontaneity of a reaction at high temperature if $$\Delta H is $$positive and $$\Delta S is $$positive?

Accepted Answer

The reaction becomes more spontaneous as temperature increases.

Question 19

Which of the following best describes the function of ATP in aerobic respiration?

Accepted Answer

ATP stores and transfers energy released from glucose oxidation for cellular work.

Question 20

A chemical reaction is carried out in a bomb calorimeter. Which of the following statements is correct?

Accepted Answer

The heat measured corresponds to the change in internal energy ($$\Delta U) at $$constant volume.

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

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