The Haber Process and NPK Fertilisers Quiz

1. Which three elements are essential for plant growth and are supplied by NPK fertilisers?

• A. Nitrogen, phosphorus and potassium
• B. Nitrogen, phosphorus and sodium
• C. Nitrogen, potassium and calcium
• D. Phosphorus, potassium and magnesium

2. In the Haber process, what is the balanced equation for ammonia synthesis?

• A. N₂ + 2H₂ ⇌ 2NH₃
• B. N₂ + 3H₂ ⇌ 2NH₃
• C. N₂ + 4H₂ ⇌ 2NH₃
• D. 2N₂ + 3H₂ ⇌ 2NH₃

3. Why is a temperature of approximately 450 °C used in the Haber process rather than a much lower temperature?

• A. Because lower temperatures would cause the iron catalyst to break down
• B. Because the pressure used would be too low at lower temperatures
• C. Because a lower temperature would slow down the reaction rate too much, even though it would give a better yield
• D. Because ammonia would decompose at lower temperatures

4. A student carries out a laboratory synthesis of ammonium sulfate fertiliser by reacting ammonia solution with dilute sulfuric acid. What is the type of chemical reaction occurring?

• A. Redox reaction
• B. Decomposition reaction
• C. Acid-base neutralisation reaction
• D. Combustion reaction

5. Explain why increasing the pressure in the Haber process increases ammonia yield but is not used at extremely high pressures in industry.

• A. High pressure increases yield because the forward reaction is favoured by Le Chatelier's principle, but extremely high pressures are avoided because the equipment is expensive, difficult to maintain and hazardous
• B. High pressure increases yield because it speeds up the reaction, but extremely high pressures cause the iron catalyst to fail
• C. High pressure increases yield because it lowers the temperature needed, but extremely high pressures cause ammonia to decompose
• D. High pressure increases yield by shifting equilibrium, but extremely high pressures reduce the effectiveness of the iron catalyst