Q: A student mixes 50.0 mL of 2.11 M HCl with 50.0 mL of 2.11 M NaOH in a coffee-cup calorimeter. The temperature rises from 24.0°C to 38.2°C. If the calorimeter constant is 4.2 cal/°C and the density and specific heat of the solution are the same as water (d = 1.00 g/mL, s = 1.00 cal/g°C), what is the total heat released by the reaction?

$$q = (100.0\ \text{g}) \times (1.00\ \text{cal/g}^\circ\text{C}) \times (14.2\ ^\circ\text{C}) + (4.2\ \text{cal}/^\circ\text{C}) \times (14.2\ ^\circ\text{C}) = 1420\ \text{cal} + 59.64\ \text{cal} = 1479.64\ \text{cal}$$

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

$$\text{Heat} = 0.113\ \text{mol} \times \frac{-368\ \text{kJ}}{2\ \text{mol}} = -20.8\ \text{kJ}$$

Q: Using the equation $$q = m \times s \times \Delta T$$, what is the heat absorbed by 200 g of water when its temperature increases from 20°C to 30°C? (Specific heat of water $$s = 4.18\ \text{J/g}^\circ\text{C})$$

$$q = 200 \times 4.18 \times 10 = 8360\ \text{J}$$

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

$$\text{H}_2O (l) \rightarrow \text{H}_2O (g)$$

Question 1

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

Accepted Answer

It measures the heat released or absorbed during a chemical reaction at constant pressure.

Question 2

A student mixes 50.0 mL of 2.11 M HCl with 50.0 mL of 2.11 M NaOH in a coffee-cup calorimeter. The temperature rises from 24.0°C to 38.2°C. If the calorimeter constant is 4.2 cal/°C and the density and specific heat of the solution are the same as water (d = 1.00 g/mL, s = 1.00 cal/g°C), what is the total heat released by the reaction?

Accepted Answer

$$q = (100.0\ 	ext{g}) 	imes (1.00\ 	ext{cal/g}^\circ	ext{C}) 	imes (14.2\ ^\circ	ext{C}) + (4.2\ 	ext{cal}/^\circ	ext{C}) 	imes (14.2\ ^\circ	ext{C}) = 1420\ 	ext{cal} + 59.64\ 	ext{cal} = 1479.64\ 	ext{cal}$$

Question 3

Which of the following statements about the First Law of Thermodynamics is correct?

Accepted Answer

The total amount of energy in the universe is constant.

Question 4

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

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 $$\Delta H = -368\ 	ext{kJ}$$, how much heat is liberated when 0.113 moles of sodium reacts?

Accepted Answer

$$	ext{Heat} = 0.113\ 	ext{mol} 	imes \frac{-368\ 	ext{kJ}}{2\ 	ext{mol}} = -20.8\ 	ext{kJ}$$

Question 6

Which of the following best describes the difference between $$9H$$ and $$9E$$ for a reaction?

Accepted Answer

$$\Delta H is $$the heat absorbed or released at constant pressure, while $$\Delta E is at $$constant volume.

Question 7

Which of the following processes will result in an increase in entropy ($$S$$)?

Accepted Answer

Melting of ice to liquid water.

Question 8

Using the equation $$q = m 	imes s 	imes \Delta T$$, what is the heat absorbed by 200 g of water when its temperature increases from 20°C to 30°C? (Specific heat of water $$s = 4.18\ 	ext{J/g}^\circ	ext{C})$$

Accepted Answer

$$q = 200 	imes 4.18 	imes 10 = 8360\ 	ext{J}$$

Question 9

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

Accepted Answer

Entropy increases as disorder increases.

Question 10

Which of the following is true for the standard molar enthalpy of formation ($$\Delta H_f^\circ) of $$elements in their most stable form at 298.15 K and 1.000 atm?

Accepted Answer

It is zero.

Question 11

A bomb calorimeter is used to measure:

Accepted Answer

The heat released or absorbed at constant volume.

Question 12

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

Accepted Answer

$$	ext{H}_2O (l) ightarrow 	ext{H}_2O (g)$$

Question 13

Which equation correctly represents the calculation of the entropy change for a reaction at 298 K?

Accepted Answer

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

Question 14

Which of the following best describes a spontaneous process?

Accepted Answer

A process that occurs naturally without outside influence.

Question 15

For a reaction, $$\Delta H = -22.6\ 	ext{kJ}$$ and $$\Delta S = -45.2\ 	ext{J/K}. $$For what temperature range is the reaction spontaneous?

Accepted Answer

For $$T \u003c \frac{\Delta H}{\Delta S}$$

Question 16

Which of the following is the correct sign convention for Gibbs Free Energy ($$\Delta G) $$and spontaneity?

Accepted Answer

$$\Delta G \u003c 0$$ : spontaneous

Question 17

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

Accepted Answer

Mixing increases the number of possible microstates.

Question 18

Which of the following statements about bond energy is correct?

Accepted Answer

Bond energy is the amount of energy required to break a bond in the gas phase.

Question 19

Which of the following is true about the entropy of a substance in different phases?

Accepted Answer

$$S_{	ext{gas}} \u003e S_{	ext{liquid}} \u003e S_{	ext{solid}}$$

Chemical Thermodynamics: Energy, Enthalpy, Entropy, and Spontaneity

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