Photo AI
Methanol can be manufactured in a reversible reaction as shown - AQA - A-Level Chemistry - Question 6 - 2020 - Paper 1
Question 6
Methanol can be manufactured in a reversible reaction as shown. CO(g) + 2H2(g) ⇌ CH3OH(g) ΔH° = -91 kJ mol⁻¹ Figure 3 shows how the partial pressures change with ... show full transcript
Worked Solution & Example Answer:Methanol can be manufactured in a reversible reaction as shown - AQA - A-Level Chemistry - Question 6 - 2020 - Paper 1
Step 1
Step 2
Calculate the partial pressure, in kPa, of hydrogen in the equilibrium mixture.
Answer
Given that the total pressure is 1.04 × 10⁴ kPa and the amounts of CO, H2, and CH3OH at equilibrium:
-
Calculate moles of H2:
- Initial moles of CO = 0.230 mol
- Mole ratio of H2 to CO from the reaction is 2:1, hence initial moles of H2 = 2 × 0.230 mol = 0.460 mol
- At equilibrium, moles of CO = 0.120 mol
- Moles of H2 reacted = (0.230 - 0.120) mol × 2 = 0.220 mol
- Moles of H2 remaining = 0.460 mol - 0.220 mol = 0.240 mol
-
Calculate the individual partial pressures:
-
Using the total pressure, partial pressure of H2 = (moles of H2 / total moles at equilibrium) × total pressure
-
Total moles = 0.120 + 0.240 + moles of CH3OH produced (from reaction = 0.110 mol)
-
Partial pressure of H2 = (0.240 mol / 0.470 mol) × 1.04 × 10⁴ kPa
-
Partial pressure of H2 = 0.480 × 1.04 × 10⁴ kPa ≈ 5.11 × 10³ kPa.
-
Step 3
Step 4
State the effect, if any, on the partial pressure of methanol and on the value of Kc.
Answer
Effect on partial pressure of methanol:
- The addition of more carbon monoxide shifts the equilibrium to the right, increasing the partial pressure of methanol.
Effect on value of Kc:
- The value of Kc remains unchanged as it is only affected by temperature.
Step 5
State the effect, if any, of the addition of a catalyst on the value of Kc for this equilibrium.
Answer
Effect on value of Kc:
- The addition of a catalyst has no effect on the value of Kc as catalysts speed up the rate of both forward and backward reactions equally.
Explanation:
- This means that the position of equilibrium is reached faster, but the concentrations of reactants and products at equilibrium remain unaffected.