Unit 4.3 Mastery Check

10.1 Which line represent the forward reaction? Dotted or Bold line.

10.2 How is the rate of forward reaction and the rate of reverse reaction between 17 min and 20 min?

Give a reason for your answer? HIGHER, LOWER, EQ

10.3 How does the concentration of the reactant change between the 12th and the 15th minute? Write down only INCREASES, DECREASES or NO CHANGE.

10.4 The rates of both the forward and the reverse reactions suddenly change at t = 15 minutes.

10.4.1 Give a reason for the sudden change in reaction rate.

10.4 The rates of both the forward and the reverse reactions suddenly change at t = 15 minutes.

10.4.2 Fully explain how you arrived at the answer to QUESTION 10.4.1

1.1 Which ONE of the following will have no effect on the equilibrium position of any chemical reaction?

1.2 A certain chemical reaction reaches equilibrium at 25 °C. The equilibrium constant, Kc, for the reaction at this temperature is 1,0 x 10-4.

Which ONE of the following statements regarding this reaction at equilibrium is CORRECT?

1.3 The reaction represented below reaches equilibrium in a closed container

CuO(s) + H2(g) ⇌ Cu(s) + H2O(g) ∆H < 0

Which ONE of the following changes will increase the yield of products?

1.4 The graph below represents the decomposition of N2O4(g) in a closed container according to the following equation:

N2O4(g) ⇌ 2NO2(g)

Which ONE of the following correctly describes the situation at t1?

1.5 The following reversible reaction reaches equilibrium in a closed container:

H2 (g) + I2 (g) ⇌ 2HI (g) ∆H < 0 Equilibrium was first established after 5 minutes. (The broken line on the graph represents the reverse reaction.)

What possible change could have been made to the reaction conditions at t = 10 minutes?

1.6 A mixture of SO2 gas and O2 gas was placed into a closed container at 300°C with a small amount of V2O5.

2SO2 (g) + O2 (g) ⇌ 2SO3 (g)

At certain times, various changes in the physical conditions applicable to the reaction or to the chemicals themselves, were made. The graph below represents the rate of reaction against time.

Which one of the changes below explains the change in the graph at 20 s?

1.7 Which statement is CORRECT for a system in DYNAMIC EQUILIBRIUM?

1.8 Initially, a certain amount of P(g) was placed in an empty container. The hypothetical reaction reaches equilibrium in a closed container according to the following balanced equation:

P(g) ⇌ 2Q(g) ΔH < 0

At time t, the temperature is increased. Which graph below best illustrates the resulting changes in the rates of the forward and reverse reactions after the temperature is increased?

1.9 Study the following reaction at equilibrium at a certain temperature.

2SO3(g) ⇌ O2(g) + 2SO2(g) H > 0

Which ONE of the following factors will change the Kc value?

1.10 Consider the following statements about the chemical equilibrium …

4A(s) + CD2(g) ⇌ 2A2D(s) + C(s) (ΔH < 0)

i. the reverse reaction is endothermic

ii. the equilibrium constant depends on the concentration of CD2

iii. the concentration of C increases when the temperature is decreased.

iv. adding more A(s) will increase the amount of C(s) at equilibrium

Which statements are CORRECT?

2.1 Initially 60,8 g pure carbon dioxide, CO2(g), is reacted with carbon, C(s), in a sealed container of volume 3 dm3. The reaction reaches equilibrium at temperature T according to the following balanced equation:

C(s) + CO2(g) ⇌ 2CO(g)

Define the term chemical equilibrium.

2.2 At equilibrium, it is found that the concentration of the carbon dioxide is 0,054 mol∙dm-3.

Calculate the:

2.2.1 Equilibrium constant, KC, for this reaction at temperature T

2.2 At equilibrium, it is found that the concentration of the carbon dioxide is 0,054 mol∙dm-3.

Calculate the:

2.2.2 Minimum mass of C(s) that must be present in the container to obtain this equilibrium

2.3 How will EACH of the following changes affect the AMOUNT of CO(g) at equilibrium?

Choose from INCREASES, DECREASES or REMAINS THE SAME.

2.3.1 More carbon is added to the container

2.3 How will EACH of the following changes affect the AMOUNT of CO(g) at equilibrium?

Choose from INCREASES, DECREASES or REMAINS THE SAME.

2.3.2 The pressure is increased by reducing the volume of the container at constant temperature. Use Le Chatelier’s principle to explain the answer.

2.4 The table below shows the percentages of CO2(g) and CO(g) in the container at different temperatures

Is the reaction EXOTHERMIC or ENDOTHERMIC? Refer to the data in the table and explain the answer.