Cations are classified into varius group on the basis of their behaviour against some reagents .The group reagent used for the classifaction of most common cation are `HCI,H_(2)S,NH_(4)OH,(NH_(4))_(2)CO_(3)`. Classification is based on whether a cation reacts with these reagents by the formation of precipitates or not .
An aqucous solution which is sightly acids contains cattions `Fe^(2+),Zn^(2+) and Cu^(2+)`. THe rengent added in excess to this solution would identify the separate `Fe^(2+)` ion in one step is

Options

A. `2M HCI`
B. `6M NH_(3)`
C. `6M NaOH`
D. `H_(2)S gas `

Answer

b

Explanation

`Fe^(3+) + 3NH_(4)OH rarr Fe(OH)_(3) darr ("reddish brown") +3NH_(4)^(o+)`
`Cu^(2+) + 4NH_(3) rarr underset(("blue colour soluble complex"))([Cu(NH_(3))_(4)]^(2+))`
` Zn^(2+) + 4NH_(3) rarr underset(("colourless soluble complex"))([Zn(NH_(3))_(4)]^(2+))`