(a) Can combination reaction be an oxidation reaction ?
(b) How will you test whether the gas evolved in a reaction is hydrogen ?
(c) Why does copper not evolve hydrogen on reacting with dilute sulphuric acid ?

Explanation

(a) Yes, combination reaction can be an oxidation reaction if one of the reactants is oxygen. For example,
`N_(2) (g) + O_(2)(g) to 2NO(g)`
(b) Bring a burning match - stick close to the mouth of the tube from which gas is escaping . If the gas immediately catches fire accompanied by 'pop sound', it is hydrogen.
(c) Copper is placed below hydrogen in the reactivity series. This means that it cannot liberate hydrogen from dilute sulphuric acid. In other words, displacement reaction is not possible.