Which combination cannot be used for the preparation of hydrogen gas in the laboratory ?
I. Zinc/conc. `H_(2)SO_(4)`
II. Zinc/ `HNO_(3)`
III. Pure zinc/dil. `H_(2)SO_(4)`

Options

A. I and II
B. I, II, III
C. III only
D. I and III.

Answer

B

Explanation

Zinc and conc `H_(2)SO_(2)` gives `SO_(2)` , zinc and dilute `HNO_(3)` gives `NH_(4)NO_(3)`. The reaction with pure zinc and dil `H_(2)SO_(4)` is very slow.