Tusomesasa.

The figure below was used by a student to investigate a reaction between calcium metal and water.

1. State the observations made during the reaction. (2 marks)
2. Identify gas C and state its use. (3 marks)
3. Write a balanced chemical equation for the reaction between calcium metal and water. (1 mark)
4. State the effect of the solution formed on phenolphthalein indicator. (1 mark)
5. Explain why the reaction should not be carried out using potassium metal instead of calcium. (2 marks)

Suggested resposponses

1. Calcium metal sink to the bottom; bubbles of a colourless gas;
2. Hydrogen; puts off a burning splint; with a pop sound;
3. Ca_(s) + 2H₂O_(l) —> Ca(OH)_2(aq) + H_2(g); - must be balanced else penalise fully, if no state symbols award ½ mark
4. Turns pink;
5. Potassium is very reactive; reacts explosively;