(i) Mg+HCl→MgCl2+H2↑Mg+NaOH→(OH)2+Na
(ii) Fe+HCl→FeCl3+H2↑Fe+2OH−→Fe(OH)2+2Na
(iii) Zn is amphoteric in nature, so it reacts with acid as well as base.
Zn+HCl→ZnCl2+21H2(g)↑Zn+NaOH→ZnO2−2+H2(g)↑
(iv)
Hg+NaOH→Hg+HgO+H2OHg+2HCl→Hg2Cl2+H2(g)