Question

Give reason for the following :
(a) `Conc. H_2 SO_4` cannot be used for drying `H_2`.
(b) `KMnO_4` should not be dissolved in `conc. H_2 SO_4`.

Answer 1

(a) Hydrogen sometimes ignites with the large amount of heat released when water is absorbed by `conc. H_2 SO_4`.
(b) `Mn_2 O_7` is formed when `KMnO_4` is dissolved in `conc. H_2 SO_4. Mn_2 O_7` formed is highly unstable and explosive in nature.
`2 KMnO_4 + 2 H_2 SO_4 rarr K_2 SO_4 + (MnO_3)_2 SO_4 + 2H_2 O`
`(MnO_3)_2 SO_4 + H_2 O rarr Mn_2 O_7 + H_2 SO_4`.