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This quiz contains 17 questions from a mix of 1 subtopics.

Select the correct Kc expression for the following reaction:

C2H5OH(aq) + CH3COOH(aq) ⇌ CH3COOC2H5(aq) + H2O(aq)

Kc​=[CH3​COOC2​H5​][CH3​COOH][C2​H5​OH][H2​O]​
Kc​=[CH3​COOC2​H5​][H2​O][C2​H5​OH][CH3​COOH]​
Kc​=[C2​H5​OH][CH3​COOH][CH3​COOC2​H5​][H2​O]​
Kc​=[C2​H5​OH][H2​O][CH3​COOC2​H5​][CH3​COOH]​

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What does the equilibrium constant, Kc, tell us?

the relative proportions of reactants and products

the concentration of products

the concentration of reactants

the rate of reaction

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A Kc value greater than indicates a position of equilbrium that is towards the products.

one

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What is the relationship between the value of Kc and the position of equilibrium?

the larger the value of Kc, the further the position of equilibrium lies to the left-hand side

the value of Kc has no relationship with the position of equilibrium

the larger the value of Kc, the further the position of equilibrium lies to the right-hand side

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Calculate the value of Kc, to 3 significant figures, for the following equilibrum:

H2(g) + I2(g) ⇌ 2HI(g)

The equilbrium concentrations are:

  • [H2] = 4.00 x 10-4 mol dm-3
  • [I2] = 6.00 x 10-4 mol dm-3
  • [HI] = 1.14 x 10-3 mol dm-3
5.42

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Calculate the value of Kc, to 3 significant figures, for the following equilibrum:

N2(g) + 3H2(g) ⇌ 2NH3(g)

The equilbrium concentrations are:

  • [N2] = 10.0 mol dm-3
  • [H2] = 0.100 mol dm-3
  • [NH3] = 0.750 mol dm-3
56.3

mol-2 dm6

mol-2 dm6

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Select the correct units for Kc for the following reaction:

CH3COCH3 + HCN ⇌ CH3C(CN)(OH)CH3

mol dm-3

mol-2 dm6

mol-1 dm3

mol2 dm-6

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A(g) + B(g) ⇌ C(g)

Initially there was 0.20 mol of A and 0.40 mol of B in the mixture for the reaction above. A and B reacted together to produce an equilbirium mixture containing 0.080 mol of C. The total volume of the mixture of 2.0 dm3.

Calculate the value of Kc. Give your answer to 2 significant figures.

4.2

mol-1 dm3

mol-1 dm3

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What effect does increasing the temperature have on the equilibrium constant for an exothermic reaction?

it decreases

it stays the same

it increases

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If Kc for a reaction is much greater than 1, what can be said about the position of equilibrium?

products predominate over reactants

the equilibrium position is in the middle

reactants predominate over products

the equilibrium position cannot be determined

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What is the effect of a catalyst on the equilibrium constant and the position of equilibrium?

it has no effect on the equilibrium constant or the position of equilibrium

it decreases the equilibrium constant and moves the equilibrium to the left

it increases the equilibrium constant and moves the equilibrium to the right

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In an endothermic reaction, Kc when the temperature is increased.

increases

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In an exothermic reaction, Kc when temperature is decreased.

increases

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How does Kc change when the concentration of products in a reaction at equilibirum are increased?

Kc increases

Kc stays the same

Kc decreases

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The following reaction takes place at equilibrium:

A + B ⇌ C    ΔrH = -10 kJ mol-1

Select ALL of the changes to conditions that could be made without altering the value of Kc.

decrease the temperature

add a catalyst

increase the concentration of A

increase the temperature

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What is the most likely value of Kc for a reaction that does not take place at all?

10-10

1

1010

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Select ALL of the conditions that could be changed in a reaction at equilibrium without altering the value of Kc.

catalyst

temperature

pressure

concentration

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3