Group 2: the alkaline earth metalsIB MYP Chemistry: Subtopic test

1. 1
   A firework designer in Valencia uses magnesium powder to produce a brilliant white light in a display rocket. Magnesium is a Group 2 metal, and the powder burns in the oxygen of the air.

   (a)

   Which compound is formed when magnesium burns in oxygen?

   [1 mark]

   • AMagnesium hydroxide
   • BMagnesium chloride
   • CMagnesium oxide
   • DMagnesium carbonate

   (b)

   What is the charge on a magnesium ion in this compound?

   [1 mark]

   • A2+
   • B1+
   • C2−
   • D6+

   (c)

   Write the balanced symbol equation for magnesium burning in oxygen.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A class adds a small piece of calcium to cold water in a beaker containing universal indicator. The calcium sinks, fizzes steadily, and the water turns cloudy and then purple. In a second beaker, a clean strip of magnesium ribbon in cold water produces only a few tiny bubbles over several minutes.

   (a)

   Which substances are formed when calcium reacts with cold water?

   [1 mark]

   • ACalcium oxide and hydrogen
   • BCalcium chloride and hydrogen
   • CCalcium oxide and oxygen
   • DCalcium hydroxide and hydrogen

   (b)

   What does the purple colour of the universal indicator show?

   [1 mark]

   • AThe solution is strongly acidic
   • BThe solution is alkaline
   • CThe solution is neutral
   • DThe solution contains dissolved hydrogen

   (c)

   Explain why calcium reacts more vigorously with water than magnesium.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student compares magnesium and calcium by reacting each with dilute hydrochloric acid and collecting the hydrogen in a gas syringe for 60 s. She uses the same mass of metal, 25 cm³ of the same acid and the same temperature, and repeats each test twice. Magnesium gave 16 cm³ and 20 cm³. Calcium gave 58 cm³ and 62 cm³. The magnesium was a ribbon strip and the calcium was small granules. Her hypothesis was that calcium is more reactive than magnesium.

   (a)

   Calculate the mean volume of hydrogen for each metal and state whether the results support her hypothesis.

   [3 marks]

   (b)

   Evaluate her method and suggest improvements.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farming cooperative in Kenya is considering spreading calcium hydroxide, made from quarried limestone, on its acidic soil. Calcium is a Group 2 metal so reactive that it is only found in nature in compounds such as limestone. Pure calcium metal reacts with cold water to form calcium hydroxide.

   (a)

   Describe what you would see when calcium reacts with cold water, write the balanced equation, and explain why calcium is more reactive than magnesium.

   [6 marks]

   (b)

   Discuss and evaluate whether the cooperative should spread calcium hydroxide on its soil.

   [6 marks]

   Total for question 4: 12 marks

End of questions