This question is about equilibria. 0.1.1. Give two features of a reaction in dynamic equilibrium. Feature 1 Feature 2 0.1.2. A gas-phase reaction is at equilibrium. When the pressure is increased the yield of product decreases. State what can be deduced about the chemical equation for this equilibrium. 0.1.3. Carbon monoxide and hydrogen react to form methanol. CO(g) + 2H₂(g) ⇌ CH₃OH(g) 0.430 mol of carbon monoxide is mixed with 0.860 mol of hydrogen. At equilibrium, the total pressure in the flask is 250 kPa and the mixture contains 0.110 mol of methanol. Calculate the amount, in moles, of carbon monoxide present at equilibrium. Calculate the partial pressure, in kPa, of carbon monoxide in this equilibrium mixture. 0.1.4. Give an expression for the equilibrium constant (Kc) for this reaction. 0.1.5. A different mixture of carbon monoxide and hydrogen is left to reach equilibrium at a temperature T. Some data for this equilibrium are shown in Table 1. Table 1 Partial pressure of CO 125 kPa Partial pressure of CH₃OH 5.45 kPa Kc = 1.15 × 10² kPa² Calculate the partial pressure, in kPa, of hydrogen in this equilibrium mixture. 0.1.6. Use the Kc value from Table 1 to calculate a value for Kc for the following reaction at temperature T. CH₃OH(g) ⇌ CO(g) + 2H₂(g) Give the units for Kc.

A-Level AQA Chemistry Chemical Equilibria, Le Chateliers Principle & Kc: This question is about equilibri

This question is about equilibria - AQA - A-Level Chemistry - Question 1 - 2022 - Paper 1

Question 1

This question is about equilibria. 0.1.1. Give two features of a reaction in dynamic equilibrium. Feature 1 Feature 2 0.1.2. A gas-phase reaction is at equil... show full transcript

Worked Solution & Example Answer:This question is about equilibria - AQA - A-Level Chemistry - Question 1 - 2022 - Paper 1

Step 1

Give two features of a reaction in dynamic equilibrium.

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Answer

The forward and reverse reactions proceed at equal rates.
Concentrations of reactants and products remain constant over time.

Step 2

State what can be deduced about the chemical equation for this equilibrium.

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Answer

The reaction involves gases, and an increase in pressure favors the side with fewer moles of gas.

Step 3

Calculate the amount, in moles, of carbon monoxide present at equilibrium.

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Answer

At equilibrium, the total moles is 1.07 mol (0.430 mol CO + 0.860 mol H₂ - 0.110 mol CH₃OH). Thus, the moles of carbon monoxide can be calculated as follows:

Let x be the moles of CO at equilibrium:

Remaining H₂ = 0.860 - 2(x - (0.110/2))

Using the ideal gas law and total pressures, we find:

x + (0.860 - 2x) + 0.110 = 1.07 → 0.430 mol.

Step 4

Calculate the partial pressure, in kPa, of carbon monoxide in this equilibrium mixture.

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Answer

Using the formula for partial pressure, we have:

$P_{CO} = \frac{n_{CO}}{n_{total}} \times P_{total}$

Substituting the values:
$P_{CO} = \frac{0.430}{1.07} \times 250 = 100.9 \text{ kPa}$

Step 5

Give an expression for the equilibrium constant (Kc) for this reaction.

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Answer

The equilibrium constant expression is given by:

$K_c = \frac{[CH_3OH]}{[CO][H_2]^2}$

Step 6

Calculate the partial pressure, in kPa, of hydrogen in this equilibrium mixture.

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Answer

From Table 1, using the relation for equilibrium constant:

$K_c = \frac{P_{CH_3OH}}{P_{CO} imes P_{H_2}^2}$

Rearranging gives:

$P_{H_2}^2 = \frac{P_{CH_3OH}}{K_c \times P_{CO}}$

Substituting the values:

$P_{H_2} = \sqrt{\frac{5.45}{(1.15 \times 10^2) \times (125)}} = 2.07 ext{ kPa}$

Step 7

Give the units for Kc.

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Answer

The units for Kc are mol/liter, or L/mol.

This question is about equilibria - AQA - A-Level Chemistry - Question 1 - 2022 - Paper 1

Worked Solution & Example Answer:This question is about equilibria - AQA - A-Level Chemistry - Question 1 - 2022 - Paper 1

Give two features of a reaction in dynamic equilibrium.

State what can be deduced about the chemical equation for this equilibrium.

Calculate the amount, in moles, of carbon monoxide present at equilibrium.

Calculate the partial pressure, in kPa, of carbon monoxide in this equilibrium mixture.

Give an expression for the equilibrium constant (Kc) for this reaction.

Calculate the partial pressure, in kPa, of hydrogen in this equilibrium mixture.

Give the units for Kc.

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