Question 2
When sodium sulfate, $Na_2SO_4(s)$, dissolves in water, for each formula unit that dissolves, the species formed are
$Na_2^{2+}(aq) + SO_4^{2-}(aq)$
$2Na^{2+}(aq) + SO_4^{2-}(aq)$
$Na_2^{2+}(aq) + S^{2-}(aq) + 4O^{2-}(aq)$
$Na_2SO_4(aq)$
$2Na^+(aq) + SO_4^{2-}(aq)$