State with balanced equation what happens when ?
(a) Potassium ferrocyanide is heated with `conc. H_2 SO_4`.
(b) A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated.
(c) Sodium chlorate reacts with sulphur dioxide.
(d) Chlorine gas is passed into water saturated with hydorgen sulphide.
(e) Hydrogen sulphide is passed through sodium bisulphite solution.

Explanation

(a) `CO` is evolved.
`K_4 Fe(CN)_6 6H_2 SO_4 + 6H_2 O overset (Delta)rarr`
`2K_2SO_4 + FeSO_4 + 3(NH_4)_2 SO_4 + 6 CO uarr`.
(b) Potassium chlorate is reduced while oxalic acid is oxidised.
`{:(KClO_(3)+H_(2)SO_(4) rarr KHSO_(4)+HCl +3[O]),(3H_(2)C_(2)O_(4)+3[O] rarr 6CO_(2)+3H_(2)O),(ulbar(KClO_(3)+3H_(2)C_(2)O_(4)+H_(2)SO_(4) rarr KHSO_(4)+HCl+6CO_(2)+3H_(2)O)):}`
(c) `NaClO_3` is reduced to `NaCl`
`{:(SO_(2)+2H_(2)O rarr H_(2)SO_(4)+2 [H]xx 3),(NaClO_(3)+6 [H] rarr NaCl+3H_(2)O),(ulbar(NaClO_(3) +3SO_(2)+3H_(2)O rarr 3H_(2)SO_(4)+NaCl)):}`
(d) `Cl_2 + H_2 S rarr 2HCl + S`.
(e) `{:(2NaHSO_(3) rarr NaSO_(3) +H_(2)O +SO_(2)),(SO_(2)+2H_(2)S rarr 2H_(2)O+ 3S),(ulbar(2 NaHSO_(3) +2H_(2)S rarr NaSO_(3) +3S +3H_(2)O)):}`.