Answer
(a) The pH increases.
(b) The pH decreases.
(c) The pH will stay the same.
Work Step by Step
(a)
$Na_2C_2O_4$ is formed by:
$Na^+$ (which doesn't affect the pH), and $C_2{O_4}^{2-}$ (which is a base);
When we add a base to a solution, its pH is going to increase, because it is getting more basic.
(b)
Ammonium chloride: $NH_4Cl$:
- $N{H_4}^+$ : An acid.
- $Cl^-$: Neutral compound.
When we add an acid to a solution, its pH is going to decrease, because it is getting more acidic.
(c)
$NaCl$ is formed by:
$Na^+$ (which doesn't affect the pH) and $Cl^-$ (which also doesn't);
Therefore, the pH will not change.
