Q: A coffee-cup calorimeter is used to measure the heat of a reaction. Which of the following equations is used to calculate the heat absorbed or released?

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

Q: Which of the following reactions would you expect to have a positive entropy change ($$\Delta S \u003e 0$$)?

$$\text{CaCO}_3 (s) \rightarrow \text{CaO} (s) + \text{CO}_2 (g)$$

Question 1

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

Accepted Answer

The total amount of energy in the universe is constant.

Question 2

A chemical reaction occurs in an open beaker at atmospheric pressure. Which thermodynamic quantity is most directly measured under these conditions?

Accepted Answer

The enthalpy change, $$\Delta H$$

Question 3

Which of the following is a state function?

Accepted Answer

Enthalpy, $$H$$

Question 4

A coffee-cup calorimeter is used to measure the heat of a reaction. Which of the following equations is used to calculate the heat absorbed or released?

Accepted Answer

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

Question 5

If the enthalpy change for a reaction, $$\Delta H_{rxn}$$, is negative, which of the following is true?

Accepted Answer

The reaction is exothermic.

Question 6

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

Accepted Answer

$$-20.8 kJ$$

Question 7

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 8

Which process results in an increase in entropy ($$\Delta S \u003e 0$$)?

Accepted Answer

Melting ice to form liquid water

Question 9

Which of the following best describes the relationship between $$\Delta H$$ and $$\Delta E$$ for a chemical reaction at constant pressure?

Accepted Answer

$$\Delta H = \Delta E + P\Delta V$$

Question 10

A bomb calorimeter is used to measure the heat of combustion of a substance. Which condition is held constant in this experiment?

Accepted Answer

Volume

Question 11

Which of the following reactions would you expect to have a positive entropy change ($$\Delta S \u003e 0$$)?

Accepted Answer

$$	ext{CaCO}_3 (s) ightarrow 	ext{CaO} (s) + 	ext{CO}_2 (g)$$

Question 12

Which of the following is true for a spontaneous process at constant temperature and pressure?

Accepted Answer

$$\Delta G \u003c 0$$

Question 13

Which of the following best describes the standard molar enthalpy of formation ($$\Delta H_f^\circ$$)?

Accepted Answer

The enthalpy change when one mole of a compound is formed from its elements in their standard states.

Question 14

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

Accepted Answer

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

Question 15

Which of the following changes will always increase the entropy of a system?

Accepted Answer

Dissolving a solid salt in water

Question 16

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 17

Which of the following best explains why the mixing of two different liquids is usually a spontaneous process?

Accepted Answer

Mixing increases the entropy of the system.

Question 18

Which of the following is true about the standard molar enthalpy of formation for elements in their most stable form at 298.15 K and 1 atm?

Accepted Answer

It is zero.

Question 19

Which of the following is NOT a correct statement about Gibbs Free Energy ($$\Delta G$$)?

Accepted Answer

$$\Delta G$$ tells us how fast a reaction occurs.

Chemical Thermodynamics: Energy, Enthalpy, Entropy, and Spontaneity

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