Q: Which equation is used to calculate the amount of heat absorbed or released by a substance in a coffee-cup calorimeter?

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

Q: For the reaction $$\text{C}_2\text{H}_5\text{OH} (l) + 3\text{O}_2 (g) \rightarrow 2\text{CO}_2 (g) + 3\text{H}_2\text{O} (l)$$, which equation would you use to calculate the enthalpy change using standard enthalpies of formation?

$$\Delta H_{rxn} = \sum \Delta H_f^\circ (\text{products}) - \sum \Delta H_f^\circ (\text{reactants})$$

Q: Which of the following is the correct expression for the entropy change of a reaction at 298 K?

$$\Delta S_{298}^\circ = \sum a S^\circ_{\text{products}} - \sum a S^\circ_{\text{reactants}}$$

Question 1

Which of the following best describes the function of a coffee-cup calorimeter as shown in the images above?

Accepted Answer

It measures the heat change of a reaction at constant pressure.

Question 2

Which equation is used to calculate the amount of heat absorbed or released by a substance in a coffee-cup calorimeter?

Accepted Answer

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

Question 3

A bomb calorimeter, as shown in the images, is used to measure which thermodynamic quantity?

Accepted Answer

The internal energy change at constant volume ($$\Delta E)$$

Question 4

Which of the following is true about the standard molar enthalpy of formation ($$\Delta H_f^\circ) $$for elements in their most stable form, as shown in the thermodynamic tables?

Accepted Answer

It is zero.

Question 5

Given the reaction: $$2	ext{Na} (s) + 2	ext{H}_2	ext{O} (l) ightarrow 	ext{H}_2 (g) + 2	ext{NaOH} (aq)$$ with $$\Delta H = -368 kJ$$, how much heat is released when 0.113 moles of sodium reacts?

Accepted Answer

$$-20.8 kJ$$

Question 6

Which of the following statements about entropy ($$S) is $$correct?

Accepted Answer

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

Question 7

Which process would result in the greatest increase in entropy ($$\Delta S$$)?

Accepted Answer

Sublimation of dry ice (solid CO$$_2) to CO$_2$$ gas

Question 8

For the reaction $$	ext{C}_2	ext{H}_5	ext{OH} (l) + 3	ext{O}_2 (g) ightarrow 2	ext{CO}_2 (g) + 3	ext{H}_2	ext{O} (l)$$, which equation would you use to calculate the enthalpy change using standard enthalpies of formation?

Accepted Answer

$$\Delta H_{rxn} = \sum \Delta H_f^\circ (	ext{products}) - \sum \Delta H_f^\circ (	ext{reactants})$$

Question 9

Which of the following best explains why the entropy of a gas increases as its volume increases, as shown in the images?

Accepted Answer

The number of possible microstates increases.

Question 10

Which of the following is the correct expression for the entropy change of a reaction at 298 K?

Accepted Answer

$$\Delta S_{298}^\circ = \sum a S^\circ_{	ext{products}} - \sum a S^\circ_{	ext{reactants}}$$

Question 11

Which of the following statements about Gibbs free energy ($$\Delta G) is $$correct?

Accepted Answer

$$\Delta G = 0$$ indicates the system is at equilibrium.

Question 12

A reaction has $$\Delta H = -22.6 kJ $$and $$\Delta S = -45.2 J/K. $$For what temperature range is this reaction spontaneous?

Accepted Answer

At temperatures below $$500 K$$

Question 13

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 14

Which of the following best describes the difference between $$\Delta H$$ and $$\Delta E$$ for a chemical reaction?

Accepted Answer

$$\Delta H$$ includes work done by expansion or compression, $$\Delta E$$ does not.

Question 15

Which of the following processes would have a negative entropy change ($$\Delta S \u003c 0$$)?

Accepted Answer

Condensation of steam

Question 16

Which of the following is true about the spontaneity of a reaction?

Accepted Answer

A reaction is spontaneous if $$\Delta G \u003c 0.$$

Question 17

Which of the following best explains why mixing two substances increases entropy?

Accepted Answer

Mixing increases the number of possible arrangements of particles.

Question 18

Which of the following is the correct relationship for the change in Gibbs free energy?

Accepted Answer

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

Question 19

Which of the following is true about the entropy of a perfect crystalline solid at 0 K, according to the Third Law of Thermodynamics?

Accepted Answer

It is zero.

Chemical Thermodynamics: Enthalpy, Entropy, and Free Energy

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