Question 17.SE.14: Which of these substances are more soluble in acidic solutio...

$\begin{aligned}Ni ( OH )_2(s) & \rightleftharpoons Ni ^{2+}(a q)+2 OH ^{-}(a q) \\2 OH ^{-}(a q)+2 H ^{+}(a q) & \rightleftharpoons 2 H _2 O (l) \\\hline \text{Overall:}Ni ( OH )_2(s)+2 H ^{+}(a q) & \rightleftharpoons Ni ^{2+}(a q)+2 H _2 O (l)\end{aligned}$

$\begin{aligned}CaCO _3(s) & \rightleftharpoons Ca ^{2+}(a q)+ CO _3^{2-}(a q) \\CO _3{}^{2-}(a q)+2 H ^{+}(a q) & \rightleftharpoons H _2 CO _3(a q) \\H _2 CO _3(a q) & \rightleftharpoons CO _2(g)+ H _2 O (l) \\\hline \text{Overall:}  CaCO _3(s)+2 H ^{+}(a q) & \rightleftharpoons Ca ^{2+}(a q)+ CO _2(g)+ H _2 O (l)\end{aligned}$

$\begin{aligned}BaF _2(s) & \rightleftharpoons Ba ^{2+}(a q)+2 F ^{-}(a q) \\2 F ^{-}(a q)+2 H ^{+}(a q) & \rightleftharpoons 2 HF (a q) \\\hline \text{Overall:}\quad BaF _2(s)+2 H ^{+}(a q) & \rightleftharpoons Ba ^{2+}(a q)+2 HF (a q)\end{aligned}$