Compare the reactivity of calcium and magnesium, provide balanced chemical equations for their reaction with HCl, and describe the products of burning magnesium in air and boiling magnesium oxide in w

Here is the solution to Q3a:

a)

i) Based on the experiment, calcium is more reactive. Calcium is lower in Group 2 than magnesium, and reactivity increases down the group. Therefore, calcium reacts more vigorously with dilute hydrochloric acid.

ii) The balanced chemical equations for the reactions with dilute hydrochloric acid are:
For magnesium:

$$\text{Mg(s)} + \text{2HCl(aq)} \to \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$$

For calcium:

$$\text{Ca(s)} + \text{2HCl(aq)} \to \text{CaCl}_2\text{(aq)} + \text{H}_2\text{(g)}$$

iii) When magnesium ribbon is burnt in air, it reacts with oxygen to form magnesium oxide.

$$\boxed{\text{Magnesium oxide}}$$

iv) When magnesium oxide (the product from part iii) is boiled with water, it forms magnesium hydroxide, which is a base. This base will turn red litmus paper blue.

$$\boxed{\text{Red litmus paper turns blue}}$$