1. 1
   A mechanic accidentally spills dilute sulfuric acid from a car battery onto a magnesium engine component in the workshop and notices bubbles of gas forming on the metal surface.

   (a)

   Which products are formed when magnesium reacts with dilute sulfuric acid?

   [1 mark]

   • AMagnesium sulfate and hydrogen
   • BMagnesium oxide and water
   • CMagnesium chloride and oxygen
   • DMagnesium sulfate and oxygen

   (b)

   The mechanic wants to confirm which gas is being produced at the magnesium surface. Which test correctly identifies this gas?

   [1 mark]

   • AA glowing splint relights in the gas
   • BThe gas turns limewater milky
   • CA lit splint held at the mouth of a test tube of the gas produces a squeaky pop
   • DDamp litmus paper is bleached white by the gas

   (c)

   Write a balanced symbol equation, including state symbols, for the reaction between magnesium and dilute sulfuric acid.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   At a science museum interactive display, visitors add equal-sized pieces of iron, zinc and magnesium to separate test tubes of dilute hydrochloric acid and time how long it takes for each metal to fully react, in order to work out an order of reactivity.

   (a)

   Which observation would indicate that a metal is the most reactive of the three?

   [1 mark]

   • AIt produces bubbles most slowly and takes the longest time to react fully
   • BIt produces bubbles most rapidly and reacts fully in the shortest time
   • CIt does not react with the acid at all
   • DIt changes colour but produces no gas

   (b)

   Which general word equation describes what happens when any of these three metals reacts with dilute hydrochloric acid?

   [1 mark]

   • Ametal + acid -> salt + water + carbon dioxide
   • Bmetal + acid -> salt + oxygen
   • Cmetal + acid -> metal oxide + water
   • Dmetal + acid -> salt + hydrogen

   (c)

   The visitors record that magnesium reacts fastest, zinc reacts at a moderate rate, and iron reacts slowest. Using this data, state the order of reactivity of the three metals from most to least reactive, and explain how this order is deduced from the observations.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A plumber notices that iron pipes buried in acidic soil corrode much faster than copper pipes buried in the same soil, and wants to understand the chemistry behind this difference before recommending replacement pipework.

   (a)

   Explain, in terms of reactivity, why the iron pipes corrode faster than the copper pipes.

   [3 marks]

   (b)

   Write a balanced symbol equation, including state symbols, for the reaction of iron with dilute sulfuric acid found in the acidic soil, and name the salt produced.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Engineers are choosing which metal to use for the support cables of a bridge in a region where rainwater is unusually acidic due to air pollution. They are considering low carbon steel (mostly iron) and copper.

   (a)

   Using your knowledge of the reactions of metals with acids, evaluate the suitability of each metal for this environment.

   [6 marks]

   (b)

   Suggest and justify one method the engineers could use to protect the chosen metal from reacting with the acidic rainwater over the lifetime of the bridge.

   [6 marks]

   Total for question 4: 12 marks

End of questions