Chemistry AQA A-Level 6 Markers (Paper 1) – Exam with Questions and Answers
– 100% Solved
2017 past paper - Q9.1 for figures
There are several stages in the industrial production of methanol from methane.
The first stage involves a gaseous equilibrium between the reactants (methane and steam), and
some gaseous products.
Figures 1 and 2 show the percentage conversion of methane into the gaseous products under
different conditions at equilibrium.
Deduce the optimum conditions for the industrial conversion of methane and steam into the
gaseous products. Explain your deductions. - ✔✔✔-Stage 1: Deductions from graph:
1a Yield increases as temperature increases
1b After a certain temperature yield no longer increases
1c Yield decreases as pressure increases
Stage 2: Optimum temperature and explanation
2a High temperature results in high energy costs/expensive
2b (After a certain temperature) yield no longer increases therefore there is no gain in using a
higher temperature
2c Optimum temperature is between 780-880oC
Stage 3: Optimum pressure and explanation
3a Low pressure may be too slow
3b So compromise pressure required
3c Optimum pressure is 1000-2000kPa or moderate pressure used
Discuss the role of iron as a heterogeneous catalyst in the Haber process.
3 H2 + N2 ⇌ 2 NH3
Your answer should include:
• the meaning of the term heterogeneous catalyst
, Chemistry AQA A-Level 6 Markers (Paper 1) – Exam with Questions and Answers
– 100% Solved
• how iron acts as a heterogeneous catalyst
• the factors that affect the efficiency and lifetime of the catalyst. - ✔✔✔-Stage 1
1a Heterogeneous means in a different phase/state from reactants
1b Catalyst speeds up reaction and is left unchanged OR lowers the activation energy for the
reaction
Stage 2
2a Hydrogen and nitrogen/reactants adsorb onto the surface/ active sites of the iron
2b Bonds weaken/reaction takes place
2c Products desorb/leave from the surface (of the iron)
Stage 3
3a Large surface area (of iron) by using powder or small pellets or support medium/mesh 3
b Catalyst poisoned / sulfur poisons or binds to the catalyst
3c Active sites blocked
Table 4 shows lattice enthalpies based on a perfect ionic model and lattice enthalpies from
Born-Haber cycles for three metal chlorides.
Table 4:
Theoretical / Experimental
Calcium chloride = 2223K / 2237K
Potassium chloride = 690K / 701K
Silver chloride = 770K / 905K
Discuss the values in Table 4.
– 100% Solved
2017 past paper - Q9.1 for figures
There are several stages in the industrial production of methanol from methane.
The first stage involves a gaseous equilibrium between the reactants (methane and steam), and
some gaseous products.
Figures 1 and 2 show the percentage conversion of methane into the gaseous products under
different conditions at equilibrium.
Deduce the optimum conditions for the industrial conversion of methane and steam into the
gaseous products. Explain your deductions. - ✔✔✔-Stage 1: Deductions from graph:
1a Yield increases as temperature increases
1b After a certain temperature yield no longer increases
1c Yield decreases as pressure increases
Stage 2: Optimum temperature and explanation
2a High temperature results in high energy costs/expensive
2b (After a certain temperature) yield no longer increases therefore there is no gain in using a
higher temperature
2c Optimum temperature is between 780-880oC
Stage 3: Optimum pressure and explanation
3a Low pressure may be too slow
3b So compromise pressure required
3c Optimum pressure is 1000-2000kPa or moderate pressure used
Discuss the role of iron as a heterogeneous catalyst in the Haber process.
3 H2 + N2 ⇌ 2 NH3
Your answer should include:
• the meaning of the term heterogeneous catalyst
, Chemistry AQA A-Level 6 Markers (Paper 1) – Exam with Questions and Answers
– 100% Solved
• how iron acts as a heterogeneous catalyst
• the factors that affect the efficiency and lifetime of the catalyst. - ✔✔✔-Stage 1
1a Heterogeneous means in a different phase/state from reactants
1b Catalyst speeds up reaction and is left unchanged OR lowers the activation energy for the
reaction
Stage 2
2a Hydrogen and nitrogen/reactants adsorb onto the surface/ active sites of the iron
2b Bonds weaken/reaction takes place
2c Products desorb/leave from the surface (of the iron)
Stage 3
3a Large surface area (of iron) by using powder or small pellets or support medium/mesh 3
b Catalyst poisoned / sulfur poisons or binds to the catalyst
3c Active sites blocked
Table 4 shows lattice enthalpies based on a perfect ionic model and lattice enthalpies from
Born-Haber cycles for three metal chlorides.
Table 4:
Theoretical / Experimental
Calcium chloride = 2223K / 2237K
Potassium chloride = 690K / 701K
Silver chloride = 770K / 905K
Discuss the values in Table 4.
