1. 1
   A student places a small piece of each of three metals, potassium, calcium and copper, into separate beakers of cold water. The potassium reacts violently, moving rapidly across the water's surface and igniting with a lilac flame. The calcium reacts steadily, producing a stream of bubbles and a cloudy white mixture. The copper shows no visible reaction at all.

   (a)

   Based on these reactions with water, which lists the three metals in order from most to least reactive?

   [1 mark]

   • APotassium, calcium, copper
   • BCalcium, potassium, copper
   • CCopper, calcium, potassium
   • DPotassium, copper, calcium

   (b)

   What gas is produced as calcium reacts steadily with cold water?

   [1 mark]

   • AOxygen
   • BHydrogen
   • CCarbon dioxide
   • DChlorine

   (c)

   Explain why copper does not react with cold water, in terms of the reactivity series and the tendency of metal atoms to form ions.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A bicycle manufacturer is deciding whether to use recycled steel or newly extracted steel, made from iron ore by reduction with carbon in a blast furnace, to build its bicycle frames.

   (a)

   Which process generally requires less overall energy: recycling steel, or extracting new steel from iron ore?

   [1 mark]

   • AExtracting new steel, because blast furnaces produce their own energy
   • BBoth processes require exactly the same amount of energy
   • CRecycling steel, because it avoids the energy-intensive extraction and reduction of iron ore
   • DRecycling steel, because it uses more electricity than extraction

   (b)

   Which of the following is an environmental advantage of using recycled steel rather than newly extracted steel?

   [1 mark]

   • AIt increases the amount of carbon dioxide released during manufacture
   • BIt requires mining additional iron ore
   • CIt has no effect on raw material supplies
   • DIt conserves limited supplies of iron ore and reduces the amount of waste sent to landfill

   (c)

   Describe one economic advantage and one environmental advantage of recycling steel rather than extracting new steel from iron ore.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates a reversible reaction using cobalt chloride paper. Dry, anhydrous cobalt chloride paper is blue. When water is added to the paper, it turns pink as hydrated cobalt chloride forms. When the pink paper is then gently heated, it turns back to blue as the water is driven off.

   (a)

   Explain why this colour change is described as a reversible reaction, and write a word equation showing both directions of the reaction using the symbol ⇌.

   [3 marks]

   (b)

   Explain what is meant by dynamic equilibrium, and explain whether cobalt chloride paper sealed in a container with air of constant humidity would reach dynamic equilibrium.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An industrial chemicals company operates two processes on one site: extracting zinc from zinc oxide ore using reduction with carbon, and manufacturing ammonia via the Haber process, using nitrogen extracted from the air and hydrogen obtained from natural gas, reaching a dynamic equilibrium under conditions of 450 degrees Celsius, 200 atmospheres pressure and an iron catalyst.

   (a)

   Explain why zinc must be extracted from zinc oxide by reduction with carbon, rather than by electrolysis, referring to zinc's position in the reactivity series and the costs and energy involved in each method, and explain what happens to the zinc oxide during this reduction reaction.

   [6 marks]

   (b)

   Explain why the Haber process is described as reaching a dynamic equilibrium, and explain, in terms of dynamic equilibrium, why the reaction is never allowed to run to completion, referring to the reversible symbol ⇌.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A student places a clean iron nail into a blue solution of copper sulfate. After a few minutes, the nail becomes coated with an orange-brown solid, and the blue colour of the solution fades.

   (a)

   What is the orange-brown solid deposited on the nail?

   [1 mark]

   • ACopper
   • BIron sulfate
   • CIron oxide
   • DCopper sulfate crystals

   (b)

   Which statement correctly explains why this reaction occurs?

   [1 mark]

   • ACopper is more reactive than iron, so it displaces iron from the nail
   • BIron is more reactive than copper, so it displaces copper from copper sulfate solution
   • CIron and copper are equally reactive, so a displacement reaction cannot occur
   • DThe reaction occurs because copper sulfate solution is a strong acid

   (c)

   Explain, in terms of electron transfer, why iron atoms are converted into iron ions during this reaction, and describe what happens to the copper ions.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A technician heats solid ammonium chloride in a test tube. It appears to sublime, disappearing from the hot end of the tube, then reappears as a white solid ring further up the cooler part of the tube. This occurs because ammonium chloride decomposes on heating into ammonia gas and hydrogen chloride gas, which then recombine as they cool.

   (a)

   Which of the following correctly represents this as a reversible reaction?

   [1 mark]

   • ANH4Cl(s) -> NH3(g) + HCl(g), with no reverse arrow
   • BNH3(g) + HCl(g) -> NH4Cl(s) only
   • CNH4Cl(s) ⇌ NH3(g) + HCl(g)
   • DNH4Cl(s) = NH3(g) + HCl(g)

   (b)

   In which part of the tube does the forward (decomposition) reaction mainly happen, and in which part does the reverse (recombination) reaction mainly happen?

   [1 mark]

   • AForward reaction in the cooler part of the tube; reverse reaction in the hot part
   • BBoth reactions happen only in the hot part of the tube
   • CBoth reactions happen only in the cooler part of the tube
   • DForward reaction in the hot part of the tube; reverse reaction in the cooler part

   (c)

   Explain why this would only be described as reaching a dynamic equilibrium if the tube were sealed as a closed system, rather than left open to the air as described here.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A mining company is considering biological methods, such as phytoextraction and bacterial extraction (bioleaching), to recover copper from a low-grade ore that is too poor in copper to be economical to mine by traditional methods.

   (a)

   Describe what is meant by phytoextraction and by bacterial extraction (bioleaching) as methods of obtaining a metal from a low-grade ore.

   [3 marks]

   (b)

   Evaluate the advantages and disadvantages of using these biological methods, rather than traditional mining, to extract copper from this low-grade ore.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   An ammonia manufacturing plant uses an iron catalyst in its Haber process reactor, where nitrogen and hydrogen react reversibly to form ammonia: N2(g) + 3H2(g) ⇌ 2NH3(g). After several years of use, the plant recovers and recycles the old iron catalyst rather than sending it to landfill or buying newly extracted iron.

   (a)

   Predict, giving reasons, how increasing the pressure in the reactor would affect the position of this equilibrium, and explain why a catalyst such as iron does not affect the position of the equilibrium.

   [6 marks]

   (b)

   Explain why it makes economic and environmental sense for the plant to recycle its old iron catalyst rather than send it to landfill and buy newly extracted iron, and describe how iron is extracted from iron ore if new iron were needed.

   [6 marks]

   Total for question 8: 12 marks

End of questions