Q: A loaded baked potato contains 530 Calories (kcal). How many kilojoules (kJ) does this represent? Use $$1 \text{ kcal} = 4.184 \text{ kJ}.$$

$$530 \text{ kcal} \times 4.184 \text{ kJ/kcal} = 2217.52 \text{ kJ}$$

Q: Which of the following reactions is endothermic? Select the reaction with a positive $$\Delta H.$$

$$6\text{CO}_2(\text{g}) + 6\text{H}_2\text{O}(\text{l}) \rightarrow \text{C}_6\text{H}_{12}\text{O}_6(\text{aq}) + 6\text{O}_2(\text{g}), \Delta H = +2836.8 \text{ kJ}$$

Q: A medical kit contains an instant cold pack that absorbs 312 kJ of heat when ammonium nitrate dissolves. If $$\Delta H = +26 \text{ kJ}$$ per mole for $$\text{NH}_4\text{NO}_3$$, how many moles are needed?

$$312 \text{ kJ} \div 26 \text{ kJ/mol} = 12 \text{ mol}$$

Q: Your body requires 2610 kcal to run a marathon. How many grams of glucose ($$\text{C}_6\text{H}_{12}\text{O}_6) $$are needed if $$\Delta H = +686 \text{ kcal/mol}$$ and molar mass is $$180.16 \text{ g/mol}$$?

$$\frac{2610 \text{ kcal}}{686 \text{ kcal/mol}} \times 180.16 \text{ g/mol} = 685.7 \text{ g}$$

Q: For the reaction $$2\text{NO}(\text{g}) + 2\text{H}_2(\text{g}) \rightleftharpoons \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\text{g})$$, which is the correct equilibrium constant expression?

$$K = \frac{[\text{N}_2][\text{H}_2\text{O}]^2}{[\text{NO}]^2[\text{H}_2]^2}$$

Question 1

Which of the following best describes the law of conservation of energy as it applies to chemical reactions?

Accepted Answer

Energy is neither created nor destroyed; it is converted from one form to another.

Question 2

A loaded baked potato contains 530 Calories (kcal). How many kilojoules (kJ) does this represent? Use $$1 	ext{ kcal} = 4.184 	ext{ kJ}.$$

Accepted Answer

$$530 	ext{ kcal} 	imes 4.184 	ext{ kJ/kcal} = 2217.52 	ext{ kJ}$$

Question 3

Which statement correctly describes the energy changes when a chemical bond is broken and when a new bond is formed?

Accepted Answer

Breaking a bond absorbs energy; forming a bond releases energy.

Question 4

Which of the following reactions is endothermic? Select the reaction with a positive $$\Delta H.$$

Accepted Answer

$$6	ext{CO}_2(	ext{g}) + 6	ext{H}_2	ext{O}(	ext{l}) ightarrow 	ext{C}_6	ext{H}_{12}	ext{O}_6(	ext{aq}) + 6	ext{O}_2(	ext{g}), \Delta H = +2836.8 	ext{ kJ}$$

Question 5

A medical kit contains an instant cold pack that absorbs 312 kJ of heat when ammonium nitrate dissolves. If $$\Delta H = +26 	ext{ kJ}$$ per mole for $$	ext{NH}_4	ext{NO}_3$$, how many moles are needed?

Accepted Answer

$$312 	ext{ kJ} \div 26 	ext{ kJ/mol} = 12 	ext{ mol}$$

Question 6

Your body requires 2610 kcal to run a marathon. How many grams of glucose ($$	ext{C}_6	ext{H}_{12}	ext{O}_6) $$are needed if $$\Delta H = +686 	ext{ kcal/mol}$$ and molar mass is $$180.16 	ext{ g/mol}$$?

Accepted Answer

$$\frac{2610 	ext{ kcal}}{686 	ext{ kcal/mol}} 	imes 180.16 	ext{ g/mol} = 685.7 	ext{ g}$$

Question 7

Which number on the reaction energy diagram represents the activation energy ($$E_a$$)?

Accepted Answer

2

Question 8

Based on the energy diagram, is the reaction exothermic or endothermic if the products are lower in energy than the reactants?

Accepted Answer

Exothermic

Question 9

Which of the following will increase the rate of a chemical reaction?

Accepted Answer

Adding a catalyst

Question 10

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Providing an alternative pathway with lower activation energy

Question 11

For the reaction $$2	ext{NO}(	ext{g}) + 2	ext{H}_2(	ext{g}) ightleftharpoons 	ext{N}_2(	ext{g}) + 2	ext{H}_2	ext{O}(	ext{g})$$, which is the correct equilibrium constant expression?

Accepted Answer

$$K = \frac{[	ext{N}_2][	ext{H}_2	ext{O}]^2}{[	ext{NO}]^2[	ext{H}_2]^2}$$

Question 12

Given equilibrium concentrations: $$[	ext{N}_2] = 0.012 	ext{ M}$$, $$[	ext{H}_2	ext{O}] = 0.121 	ext{ M}$$, $$[	ext{NO}] = 0.046 	ext{ M}$$, $$[	ext{H}_2] = 0.024 	ext{ M}$$ for $$2	ext{NO}(	ext{g}) + 2	ext{H}_2(	ext{g}) ightleftharpoons 	ext{N}_2(	ext{g}) + 2	ext{H}_2	ext{O}(	ext{g})$$, what is $$K$$?

Accepted Answer

$$K = \frac{(0.012)(0.121)^2$}{(0.046)^2$(0.024)^2$$} = 143.6$

Question 13

The reaction $$	ext{H}_2(	ext{g}) + 	ext{Cl}_2(	ext{g}) ightleftharpoons 2	ext{HCl}(	ext{g})$$ has $$K = 1.3 	imes 10$$^{34}$$. What does this value indicate about the equilibrium mixture?

Accepted Answer

The equilibrium mixture contains mostly products.

Question 14

Which scenario best illustrates dynamic equilibrium in a reversible chemical reaction?

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction, and concentrations remain constant.

Question 15

Which of the following changes will decrease the rate of the reaction $$	ext{N}_2(	ext{g}) + 	ext{O}_2(	ext{g}) ightarrow 2	ext{NO}(	ext{g})$$?

Accepted Answer

Removing some $$	ext{O}_2$$

Question 16

Which of the following is a real-life example of an exothermic reaction?

Accepted Answer

Combustion of methane gas

Question 17

Which energy unit is commonly used in nutrition, and how does it relate to other energy units?

Accepted Answer

The Calorie (with uppercase C), which is equal to 1 kilocalorie (kcal)

Chapter 9: Energy, Rate, and Equilibrium – Study Notes

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