Misawite is a compound of iron, oxygen and hydrogen which does not rust and gives corrosion resistance.

(i) Copper is used for making coins and ornaments along with gold and other metals.
(ii) Copper and its alloys are used for making wires, water pipes and other electrical parts.

(i) Simple roasting of some of the ores give the crude metal. In such cases, the use of and hydrogen which does not rust and gives reducing agents is not necessary.
(ii) For example, mercury is obtained by Write the chemical composition of the roasting of its ore cinnabar (HgS)
\(Hg{ S }_{ (s) }+{ O }_{ 2(g) }\longrightarrow { Hg }_{ (I) }+{ SO }_{ 2 }\uparrow \)

(i) This method can be applied to the oxides of the metals (Fe, Pb, Cu) having less electropositive character than hydrogen
\(\mathrm{Ag}_{2} \mathrm{O}_{(s)}+\mathrm{H}_{2(g)} \longrightarrow 2 \mathrm{Ag}_{(s)}+\mathrm{H}_{2} \mathrm{O}_{(l)}\)
(ii) Nickel oxide can be reduced to nickel by using a mixture of hydrogen and carbon monoxide (water gas)
(iii) \({ 2NiO }_{ (s) }+{ CO }_{ (g) }+{ H }_{ 2(g) }\longrightarrow 2{ Ni }_{ (s) }+{ CO }_{ 2(g) }+{ H }_{ 2 }{ O }_{ (l) }\)

(i) If value of \(\triangle\)G is fur any reaction then to make such reaction spontaneous it is coupled with another reaction of large negative \(\triangle\)G value, so that the sum of two \(\triangle\)G becomes negative. This is known as coupling of reaction.
(ii) In the metallurgy, thermodynamically infeasible reaction is coupled with a reaction which has more negative G, so that net \(\triangle\)G become negative.