Answer
a.
$2HClO_4(aq) + Mg(OH)_2(s) -- \gt Mg(ClO_4)_2(aq) +2 H_2O(l)$
$_{2H^+(aq) + 2ClO_4^-(aq) + Mg(OH)_2(s) -- \gt Mg^{2+}(aq) + 2ClO_4^-(aq) +2 H_2O(l)}$
$2H^+(aq) + Mg(OH)_2(s) -- \gt Mg^{2+}(aq) + 2H_2O(l)$
b.
$HCN(aq) + NaOH(aq) -- \gt NaCN(aq) + H_2O(l)$
$_{H^+(aq) + CN^-(aq) + Na^+(aq) + OH^-(aq) -- \gt Na^+(aq) + CN^-(aq) + H_2O(l)}$
$H^+(aq) + OH^-(s) -- \gt H_2O(l)$
c.
$HCl(aq) + NaOH(aq) -- \gt NaCl(aq) + H_2O(l)$
$_{H^+(aq) + Cl^-(aq) + Na^+(aq) + OH^-(aq) -- \gt Na^+(aq) + Cl^-(aq) + H_2O(l)}$
$H^+(aq) + OH^-(aq) -- \gt H_2O(l)$
Work Step by Step
a.
1. Write an double replacement reaction between the ionic compounds:
$HClO_4(aq) + Mg(OH)_2(s) -- \gt Mg(ClO_4)_2(aq) + H_2O(l)$
- Balance it:
$2HClO_4(aq) + Mg(OH)_2(s) -- \gt Mg(ClO_4)_2(aq) +2 H_2O(l)$
2. Separate the aqueous compounds into ions:
$2H^+(aq) + 2ClO_4^-(aq) + Mg(OH)_2(s) -- \gt Mg^{2+}(aq) + 2ClO_4^-(aq) +2 H_2O(l)$
- This is the complete ionic equation.
3. Remove the spectator ions: (Those that don't change after the reaction)
$2H^+(aq) + Mg(OH)_2(s) -- \gt Mg^{2+}(aq) + 2H_2O(l)$
--------------
b.
1. Write an double replacement reaction between the ionic compounds:
$HCN(aq) + NaOH(aq) -- \gt NaCN(aq) + H_2O(l)$
- It is already balanced
2. Separate the aqueous compounds into ions:
$H^+(aq) + CN^-(aq) + Na^+(aq) + OH^-(aq) -- \gt Na^+(aq) + CN^-(aq) + H_2O(l)$
- This is the complete ionic equation.
3. Remove the spectator ions: (Those that don't change after the reaction)
$H^+(aq) + OH^-(s) -- \gt H_2O(l)$
----------------------------
c.
1. Write an double replacement reaction between the ionic compounds:
$HCl(aq) + NaOH(aq) -- \gt NaCl(aq) + H_2O(l)$
- It is already balanced
2. Separate the aqueous compounds into ions:
$H^+(aq) + Cl^-(aq) + Na^+(aq) + OH^-(aq) -- \gt Na^+(aq) + Cl^-(aq) + H_2O(l)$
- This is the complete ionic equation.
3. Remove the spectator ions: (Those that don't change after the reaction)
$H^+(aq) + OH^-(aq) -- \gt H_2O(l)$