How oxides of metals are reduced by hydrogen ?

Explanation

(i) This method can be applied to the oxides of the metals (Fe, Pb, Cu) having less electropositive character than hydrogen.
`Ag_(2)O_((s)) + H_(2(g)) rarr 2Ag_((s)) + H_(2)O_((l))`
(ii) Nickel oxide can be reduced to nickel by using a mixture of hydrogen and carbon monoxide (water gas)
(iii) `2NiO_((s)) + CO_((g)) + H_(2(g)) rarr 2Ni_((s)) + CO_(2(g)) + H_(2)O_((l))`