1. 1
   A maintenance team inspecting an old iron road bridge finds patches of a reddish-brown, flaky substance on the exposed steel girders, which has weakened the metal in places, and they discuss ways to prevent this from happening on a newly built section of the bridge.

   (a)

   What two substances must both be present for iron to rust in this way?

   [1 mark]

   • AWater and oxygen
   • BWater and carbon dioxide
   • COxygen and nitrogen
   • DCarbon dioxide and nitrogen

   (b)

   The engineers decide to coat the new steel girders with a thin layer of zinc to protect them from rusting. Which term describes this method of protection?

   [1 mark]

   • AElectrolysis
   • BGalvanising
   • CNeutralisation
   • DFractional distillation

   (c)

   Explain why coating the steel girders with zinc still protects the iron underneath from rusting even if the zinc coating becomes scratched, exposing the iron beneath.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A jeweller explains to a customer that a gold ring found in an ancient tomb still looks bright and untarnished after thousands of years, unlike an iron object recovered from the same site, which has almost completely rusted away.

   (a)

   What does this observation suggest about the reactivity of gold?

   [1 mark]

   • AGold reacts with oxygen to form a protective rust-like layer, just like iron
   • BGold is very reactive, but reacts too slowly to be observed
   • CGold is very unreactive, so it does not readily react with substances in its environment
   • DGold is more reactive than iron but does not conduct electricity

   (b)

   The jeweller adds that gold, unlike most other metals, is sometimes found in the ground as the pure, uncombined element. Which statement best explains why this is possible for gold?

   [1 mark]

   • AGold is a non-metal, so it does not follow the same rules as reactive metals
   • BGold reacts readily with oxygen but the compound formed looks identical to pure gold
   • CGold is extracted only by electrolysis, so it must already exist as a compound underground
   • DGold is so unreactive that it does not readily form compounds with other elements in the environment

   (c)

   Place gold, iron and potassium in order of increasing reactivity, and explain how the ancient tomb evidence described above supports the position of gold in this order.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student adds a piece of zinc metal to a beaker of blue copper(II) sulfate solution and observes that the blue colour of the solution gradually fades while a reddish-brown solid forms on the surface of the zinc.

   (a)

   A student adds a piece of zinc metal to a blue solution of copper(II) sulfate and observes that the blue colour fades while a reddish-brown solid coats the zinc. Write the balanced symbol equation for this reaction and explain, in terms of oxidation and reduction, what happens to the zinc and copper during the reaction.

   [3 marks]

   (b)

   The student then repeats the experiment using a piece of silver instead of zinc, added to the same blue copper(II) sulfate solution, and observes no colour change and no solid forming. Explain this result and use it, together with the previous result, to place zinc, copper and silver in order of reactivity.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A shipping company wants to protect the steel hull of a cargo ship from rusting in seawater over many years of continuous use, and is comparing several possible methods with its engineering team.

   (a)

   Describe two different methods that could be used to prevent the steel from rusting, and explain, in terms of reactivity and redox reactions, why each method is effective.

   [6 marks]

   (b)

   The engineering team also considers using a large block of copper instead of zinc for sacrificial protection. Explain, using the reactivity series, why copper would not be a suitable choice for this purpose, and describe what would happen to the steel hull if copper were used instead.

   [6 marks]

   Total for question 4: 12 marks

End of questions