Question

Test to distinguish between ZnSO4 and ZnSO3?

Answer 1

Add to barium chloride solution followed by around `2cm^3` of dilute `"HCl"`

Explanation:

Barium chloride solution will react with a metal sulphate or metal sulphite to form a metal chloride and barium sulphate or barium sulphite according to one of the following reactions:
`"BaCl"_2+"MSO"_4-> "MCl"_2+"BaSO"_4`
or
`"BaCl"_2+2"MSO"_4-> 2"MCl"+"BaSO"_4`

or

`"BaCl"_2+"MSO"_3-> "MCl"_2+"BaSO"_3`
or
`"BaCl"_2+"M"_2"SO"_3-> 2"MCl"+"BaSO"_3`

(depending on the metal (`"M"`) used.)

In either case, barium sulphate or barium sulphite is produced, which are insoluble in water and therefore form a white precipitate.

However, by adding around `2cm^3` of dilute `"HCl"` the difference can be found. If the reaction produces barium sulphate then the white precipitate will be insoluble in dilute `"HCl"`, however barium sulphite is soluble in `"HCl"`.