Saline hydrides are known to react with water violently producing fire, Can `CO_(2)` , a well known fire extinguisher, be used in this case? Explain.

Explanation

The saline hydrides (e.g., NaH, `CaH_(2)` etc.) react with water violently to yield the corresponding metal hydroxides with evolution of `H_(2)` gas. The liberated `H_(2)` gas undergoes spontaneous combustion causing fire and this is because of highly exothermic nature of the combustion reaction.
NaH(s) + `H_(2)`O(l) `rarr` NaOH(aq) + `H_(2)`(g),
`2H_(2) + O_(2) rarr 2H_(2)O(l) , DeltaH^(0)` = - 286J`cdot "mol"^(-1)`
In this case, `CO_(2)` cannot used as a fire extinguisher because it gets reduced by the hot metal hydride to form formate ion.
`overset(-1)(" NaH ") + overset(+4)(" CO_(2) ") rarr overset(+1+2)(" HCOON")`