ph value

a. When a piece of magnesium ribbon is added to diluted hydrochloric acid, magnesium chloride and hydrogen is formed.
Chemical equation:
Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

Initially, the solution has a pH value lower than 7 as HCl is an acid. After the reaction, the products formed are neutral, which have a pH value higher than 7.

Therefore, the pH value increases.


b. Water is neutral in nature, which implies it has a pH value of 7. When hydrogen chloride gas is bubbled into water, it dissolves and ionizes in water to give H+ ions since it is an acid. H+ ions are responsible for lowering the pH value of a solution. As a result, the pH value should decrease as the solution turns from neutral to acidic.

HCl (g) → H+ (aq) + Cl- (aq)