Justify that the reaction :
`2Na_((s))+H_(2(g))to2NaH_((s))` is a redox reaction.

Explanation

Since in the above reaction the compound formed is an ionic compound, which may also be represented as `Na^(+)N_((s))^(-)`, this suggests that one half reaction in this process is :
`2Na_((s))to2Na_((g))^(-)+2e^(-)`
and the other half reaction is :
`H_(2(g))+2e^(-)to2H_((g))^(-)`
This splitting of the reaction under examination into two half reactions automatically reveals that here sodium is oxidised and hydrogen is reduced, therefore, the complete reaction is a redox change.