Calcium reacts with cold water to form calcium hydroxide, Ca(OH)₂, and hydrogen, H₂.

a. State the oxidation number of calcium in:

i. Calcium metal

ii. Calcium hydroxide.

b. State the oxidation number of hydrogen in:

i. Water

ii. Hydrogen gas.

c. Write two half-equations for the reaction between water and calcium hydroxide to show:

i. The change from calcium to calcium ions

ii. The change from water to hydroxide ions and hydrogen.

d. In which one of the half-equations in part c is a reduction occurring? Give a reason for your answer.

e. Write a balanced equation for the reaction of calcium with water.

f. Explain the role played by water in this reaction.