Metal reactivity and displacementIB MYP Chemistry: Subtopic test

1. 1
   A teacher in Doha demonstrates the reactions of metals with cold water. She adds small pieces of potassium, calcium and copper to separate troughs of water. The potassium moves across the surface and burns with a lilac flame, the calcium fizzes steadily and the copper does not react.

   (a)

   Which gas is produced when potassium and calcium react with cold water?

   [1 mark]

   • AOxygen
   • BCarbon dioxide
   • CNitrogen
   • DHydrogen

   (b)

   Which of these metals is the most reactive?

   [1 mark]

   • APotassium
   • BCalcium
   • CMagnesium
   • DCopper

   (c)

   Write the word equation for the reaction of calcium with water and state the test for the gas produced.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Dublin adds equal-sized pieces of magnesium, zinc, iron and copper to separate test tubes of dilute hydrochloric acid. Bubbles form rapidly with magnesium, steadily with zinc and slowly with iron, and there are no bubbles with copper.

   (a)

   Which list shows the metals in order of reactivity, with the most reactive first?

   [1 mark]

   • ACopper, iron, zinc, magnesium
   • BMagnesium, zinc, iron, copper
   • CZinc, magnesium, iron, copper
   • DIron, zinc, magnesium, copper

   (b)

   Which statement explains why copper does not react with dilute hydrochloric acid?

   [1 mark]

   • ACopper is above hydrogen in the reactivity series
   • BCopper is a non-metal
   • CCopper is below hydrogen in the reactivity series
   • DCopper is a liquid at room temperature

   (c)

   Write a balanced symbol equation for the reaction of magnesium with dilute hydrochloric acid.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students at a school in Seoul investigate displacement reactions. They add 1.0 g of magnesium powder, zinc powder or iron powder to 25 cm³ of copper(II) sulfate solution in a polystyrene cup with a lid, stir, and record the highest temperature reached. A pink-brown solid forms in each cup.

   (a)

   State a hypothesis for the investigation, including a prediction of the order of the temperature rises, and give a scientific reason.

   [3 marks]

   (b)

   The temperature rises were: magnesium 27 °C, zinc 17 °C and iron 9 °C. State whether the results support the hypothesis, using evidence. Write the word equation for zinc reacting with copper(II) sulfate, state which substance is oxidised, and suggest one improvement.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A city council in Mexico is choosing the metal for new water pipes in an area where the tap water is slightly acidic. Iron pipes cost much less than copper pipes. Copper pipes are lighter and can be recycled. In similar areas, iron pipes have usually needed replacing after about 40 years, while copper pipes have lasted for more than 70 years. Copper has to be mined, which uses a lot of energy and damages land.

   (a)

   Explain how the reactivity series can be used to predict which of iron and copper pipes would last longer in slightly acidic water.

   [6 marks]

   (b)

   Discuss the benefits and drawbacks of using copper rather than iron for the new pipes, and evaluate which metal the council should choose.

   [6 marks]

   Total for question 4: 12 marks

End of questions