Chemistry

Problem

When a reagent (X) reacts with

\text{Fe}^{3+}

salt solution turns red due to the formation of a compound (Y). This reagent causes no change in colour with

\text{Fe}^{2+}

salt solution. Compound (X) and (Y) are respectively : a.

\text{NH}_4\text{SCN}

and

\text{Fe}(\text{SCN})_3

\text{K}_4[\text{Fe}(\text{CN})_6]

and

\text{FeSO}_4

\text{Na}_2\text{HPO}_4

and

\text{FeSO}_4

\text{K}_3[\text{Fe}(\text{CN})_6]

and

\text{K}_2\text{Fe}[\text{Fe}(\text{CN})_6]