Sec 4 Chemistry Ammonia & Equilibrium topical questions

Cobalt(II) chloride paper is blue when dry and pink when wet. Write the reversible-reaction sentence (words are fine) describing both directions.

State what is meant by dynamic equilibrium.

Write the balanced equation for the Haber process, including the state symbols.

Name the three conditions used industrially in the Haber process and the catalyst employed.

Describe how a dry sample of ammonia gas is prepared in the laboratory from a solid mixture.

1. (a)Name the two solid reagents and write the equation.[2]
2. (b)State the collection method and the drying agent.[2]

Ammonia is one of the most produced chemicals in the world.

1. (a)Name two major uses of ammonia.[1]
2. (b)Name the acid that reacts with ammonia to give ammonium nitrate.[1]
3. (c)State the ion that makes aqueous ammonia alkaline.[1]

Explain why a temperature lower than 450 °C would give a higher yield of ammonia but is not used industrially.

Ammonia solution is neutralised by dilute sulfuric acid.

1. (a)Write the equation for the reaction.[2]
2. (b)Name the salt and state which plant nutrient (N, P or K) it provides.[2]

Describe how a pure, dry sample of ammonium nitrate can be prepared from ammonia solution and nitric acid in the laboratory.

The Haber reactor is run at about 200 atm. Higher pressures would give more ammonia per pass.

1. (a)Explain, in terms of moles of gas, why higher pressure increases the yield.[2]
2. (b)State two reasons the pressure is not raised beyond about 200 atm.[2]

A chemist claims: "At equilibrium in the Haber reactor, the concentrations of nitrogen, hydrogen and ammonia are all equal." Correct the claim with reasoning.

Complete the table of industrial conditions for the Haber process and justify each.

1. (a)Give the three missing values.[3]
2. (b)Explain why the pressure is not pushed far higher in practice.[1]

Inside a sealed Haber reactor, the mixture of N₂, H₂ and NH₃ reaches a steady state.

1. (a)Explain the term dynamic equilibrium.[2]
2. (b)Explain why the reactor must be sealed (closed) for equilibrium to be established.[2]

Equilibrium mixtures leave a Haber reactor at different temperatures; the pressure is fixed at 200 atm.

1. (a)Describe the trend in the data.[1]
2. (b)Explain the trend using the fact that the forward reaction is exothermic.[2]
3. (c)State one reason the factory still runs at about 450 °C.[2]

A farm over-fertilises a field beside a river. After a storm, fish are later found dead in the river.

1. (a)Describe the chain of events linking the fertiliser to the dead fish.[4]
2. (b)Suggest one farming practice that would reduce the risk.[1]
3. (c)Name the nutrient ion in most nitrogenous fertilisers that plants absorb.[1]

The Haber process converts only a fraction of the gases on each pass through the reactor, yet almost no nitrogen or hydrogen is wasted overall.

1. (a)Explain how the plant achieves near-complete use of the gases.[2]
2. (b)State how the ammonia is separated from the unreacted gases, using your knowledge of ammonia's properties.[2]
3. (c)Explain why the iron catalyst does not need replacing after each pass but does slowly need topping up over months.[2]

A student compares two possible fertiliser recipes per 100 g of product: brand X is pure ammonium nitrate (Mr = 80); brand Y is pure ammonium sulfate (Mr = 132).

1. (a)Calculate the mass of nitrogen atoms in 100 g of brand X.[2]
2. (b)Calculate the mass of nitrogen atoms in 100 g of brand Y.[2]
3. (c)State which brand delivers more nitrogen per gram and give one other factor a farmer should weigh before choosing.[2]

A farmer compares urea, CO(NH₂)₂ (Mr = 60), with ammonium nitrate, NH₄NO₃ (Mr = 80), as nitrogen fertilisers (N = 14, C = 12, O = 16, H = 1).

1. (a)Calculate the percentage by mass of nitrogen in urea.[2]
2. (b)Calculate the percentage by mass of nitrogen in ammonium nitrate.[2]
3. (c)State which is richer and give one practical drawback of the richer fertiliser.[2]