Hydrochloric acid reacts with magnesium oxide (a basic oxide) to form a salt and water.

b)

(i)
Hydrochloric acid reacts with magnesium oxide (a basic oxide) to form a salt and water.

$$\text{Hydrochloric acid} + \text{Magnesium oxide} \longrightarrow \text{Magnesium chloride} + \text{Water}$$

(ii)
Hydrochloric acid reacts with zinc metal (a metal above hydrogen in the reactivity series) to form a salt and hydrogen gas.

$$\text{Hydrochloric acid} + \text{Zinc} \longrightarrow \text{Zinc chloride} + \text{Hydrogen}$$

(iii)
Hydrochloric acid reacts with calcium hydrogen carbonate (a hydrogen carbonate) to form a salt, water, and carbon dioxide gas.

$$\text{Hydrochloric acid} + \text{Calcium hydrogen carbonate} \longrightarrow \text{Calcium chloride} + \text{Water} + \text{Carbon dioxide}$$

(iv)
Hydrochloric acid reacts with potassium hydroxide (a base) in a neutralization reaction to form a salt and water.

$$\text{Hydrochloric acid} + \text{Potassium hydroxide} \longrightarrow \text{Potassium chloride} + \text{Water}$$