Write the following redox reactions using half cell rections
`(i) Zn(s)+FeCI_(2)(aq)rarrZnCI_(2)(aq)+Fe(s)`
`(ii)Mg(s)+CI_(2)(g)rarrMgCI_(2)(s)`
`(iii)Mg(s)+2H^(+)(aq)rarrMg^(2+)(aq)+H_(2)(g)`