(a) Why is combustion reaction an oxidation reaction ?
(b) How will you test whether the gas evolved in a reaction is hydrogen ?
(c) Why does not silver evolve hydrogen on reacting with dillute sulphuric acid ?

Explanation

(a) Combustion reaction is an oxidation reaction because it is always carried in the presence of air or oxygen. For example,
`CH_(4)(g) + 2O_(2)(g) to CO_(2)(g) + 2H_(2)O (l)`
(b) Bring a burning match stick close to the mouth of the tube from which hydrogen gas escapes. The gas will immediately catch fire and this will be accompanied by pop sound.
(c) Silver is a less reactive metal in the sense that it occupies a place below hydrogen in the reactivity series. Therefore it does not evolve hydrogen gas on reacting with either dilute sulphuric acid or dilute hydrochloric acid.