Question

Concentrated sodium hydroxide can separate a mixture of
A. `Al^(3+)` and `Cr^(3+)`
B. `Cr^(3+)` and `Fe^(3+)`
C. `Al^(3+)` and `Zn^(2+)`
D. `Zn^(2+)` and `Pb^(2+)`

Answer 1

`Cr^(3+) + 3OH^(-) to underset("Dirty green ppt.")(Cr(OH)_(3)) `
`2Cr(OH)_(3)+4NaOH +3[O] to underset("soluble yellow soluiton")(2Na_(2)CrO_(4))+5H_(2)O`
`Fe^(3+) +3OH^(-) to underset("Brown ppt.")(Fe(OH)_(3))`
`Fe(OH)_(3)` is not affected by conc. NaOH