What will happen ?(Also write the chemical equations).
(a)When a filter paper moistened with potassium iodate and starch solution is brought in contact with sulphur dioxide gas.
(b)When `H_(2)S` gas is made to react with sodium tetrahydroxidoplumbate `(II)` solution.

Explanation

(a)Blue colouration develops due to the formation of iodine gas.
`5 SO_(2)+2lO_(3)^(-)+4 H_(2)Otol_(2)+5 SO_(4)^(2-)+2 H^(+)`
`I_(2)` +"starch"to "Blue"("starch iodine absorption complex")
(b)Black precipitate is formed owing to the formation of `PbS`.
`[Pb(OH)_(4)]^(2-)+H_(2)StoPbSdarr+2OH^(-)+2 H_(2)O`