Zinc reacts with dilute `H_(2)SO_(4)` to give `H_(2)`. It also reacts with conc. `H_(2)SO_(4)` to give `SO_(2)` . How will you account for this difference ?

Explanation

Dilute `H_(2)SO_(4)` behaves as a proton acid and zinc metal displaces hydrogen from the acid.
`Zn+H_(2)SO_(4)("dil")to ZnSO_(4)+H_(2)`
Concentrated `H_(2)SO_(4)` behaves as a strong oxidising agent and itself is reduced to `SO_(2)`.
`Zn +2H_(2)SO_(4) ("conc.")to ZnSO_(4)+SO_(2)+2H_(2)O`