When a reagent (X) reacts with Fe3+ salt solution turns red due to the formation of a compound (Y). This reagent causes no change in colour with Fe2+ salt solution. Compound (X) and (Y) are respectively :
(1) NH4SCN and Fe(SCN)3
(2) K4[Fe(CN)6] and FeSO4
(3) Na2HPO4 and FeSO4
(4) K3[Fe(CN)6] and K2Fe[Fe(CN)6]