Answer
See answer below.
Work Step by Step
a) Balanced equation
$Zn(s)+2\ HCl(aq)\rightarrow H_2(g)+ZnCl_2(aq)$
Net ionic equation:
$Zn(s)+2\ H_3O^+(aq)\rightarrow H_2(g)+Zn^{2+}(aq)+H_2O(l)$
b) Balanced equation
$Mg(OH)_2(s)+2\ HCl(aq)\rightarrow 2\ H_2O(l)+MgCl_2(aq)$
Net ionic equation:
$Mg(OH)_2(s)+2\ H_3O^+(aq)\rightarrow Mg^{2+}(aq)+4\ H_2O(l)$
c) Balanced equation
$CaCO_3(s)+2\ HNO_3(aq)\rightarrow H_2O(l)+CO_2(g)+Ca(NO_3)_2(aq)$
Net ionic equation:
$CaCO_3(s)+2\ H_3O^+(aq)\rightarrow Ca^{2+}(aq)+3\ H_2O(l)+CO_2(g)$
d) Balanced equation
$(NH_4)_2S(aq)+FeCl_2(aq)\rightarrow 2\ NH_4Cl(aq)+FeS(s)$
Net ionic equation:
$S^{2-}(aq)+ Fe^{2+}(aq)\rightarrow FeS(s)$
