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

Which combination cannot be used for the preparation of hydrogen gas i

1.	Which combination cannot be used for the preparation of hydrogen gas in the laboratory ? I. Zinc/conc. H_(2)SO_(4) II. Zinc/dil. HNO_(3) III. Pure zinc/dil. H_(2)SO_(4)
Answer» I and II I,II,III III only I and III. Solution :Zinc and conc. `H_(2)SO_(4)` given `SO_(2)` , zinc and dilute `HNO_(3)` gives `NH_(4)SO_(4)`. The reaction with PURE zinc and dil. `H_(2)SO_(4)` is very low.