Chapter 5 Practice Paper: Ammonia and Reversible Reactions — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   White anhydrous copper(II) sulfate is exposed to moist air and turns blue. In CuSO₄·5H₂O ⇌ CuSO₄ + 5H₂O, this colour change is

   1. Adriven to the right by adding water
   2. Bdriven to the left by adding water
   3. Cdriven to the right by heating
   4. Dunchanged by any conditions
   ( )
2. 2

   Which statement about a reaction mixture at dynamic equilibrium is TRUE?

   1. ABoth reactions have stopped.
   2. BThe forward rate equals the reverse rate.
   3. CThe concentrations of reactants equal the concentrations of products.
   4. DThe mixture must be at constant temperature and cannot be disturbed.
   ( )
3. 3

   In the Haber process, increasing the pressure from 100 atm to 200 atm

   1. Aincreases the yield of ammonia because fewer gas moles are on the ammonia side
   2. Bdecreases the yield because the catalyst is compressed
   3. Chas no effect since the catalyst controls the yield
   4. Dincreases the rate by raising the activation energy
   ( )
4. 4

   The iron catalyst in the Haber process is best described as

   1. Aa substance that shifts the equilibrium towards ammonia
   2. Ba substance consumed slowly to provide hydrogen
   3. Ca substance that speeds both directions so equilibrium is reached sooner
   4. Da substance that raises the temperature of the reactor
   ( )
5. 5

   Which fertiliser salt supplies phosphorus?

   1. Aammonium nitrate
   2. Bpotassium chloride
   3. Ccalcium phosphate
   4. Dammonium sulfate
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Include state symbols where the question asks, and balance every equation.

1. 1

   The Haber process manufactures ammonia: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). The forward reaction is exothermic.

   1. (a)

      State the temperature, pressure and catalyst used.

      [2]
   2. (b)

      Explain why the temperature chosen is a compromise between yield and rate.

      [2]
   3. (c)

      State what happens to the unreacted nitrogen and hydrogen, and why this matters economically.

      [2]
2. 2

   Ammonia is converted into fertiliser salts.

   1. (a)

      Write the equation for ammonia reacting with nitric acid, and name the salt.

      [2]
   2. (b)

      A student prepares the same salt by the excess-solid method. Explain why this cannot work here.

      [2]
   3. (c)

      Name the acid needed to make ammonium phosphate, and state the plant nutrient it supplies besides nitrogen.

      [1]
3. 3

   Blue cobalt(II) chloride paper is used as a test for water: CoCl₂ (blue) + water ⇌ CoCl₂·6H₂O (pink).

   1. (a)

      State which direction of the equilibrium the paper shows when it turns pink, and name the species being formed.

      [2]
   2. (b)

      Describe how the paper could be returned to blue, and state what this shows about the reaction.

      [2]
4. 4

   A river beside farmland receives heavy fertiliser run-off after a storm. Weeks later, water samples show very low dissolved oxygen.

   1. (a)

      Describe the full chain of events that lowered the oxygen.

      [3]
   2. (b)

      State the technical name for this process.

      [1]
   3. (c)

      Suggest one change in farming practice to reduce the run-off.

      [1]