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To avoid the precipitation of hydroxides...

To avoid the precipitation of hydroxides of `Ni^(2+),Co^(2+),Zn^(2+) and Mn^(2+)` along with those of `Fe^(3+),Al^(3+) and Cr^(3+)` the third group solution should be:

A

Heated with a few drops of conc. `HNO_(3)`

B

Treated with excess of `NH_(4)Cl`

C

`H_(2)S` gas is passed into solution

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
B
The value of `K_(sp)` of hydroxides of `Fe^(3+),Cr^(3+),Al^(3+)` are lower than that of `Co^(2+),Ni^(2+),Mn^(2+) and Zn^(2+)` Therefore, in the presence of `NH_(4)Cl`, dissociation of `NH_(4)OH` suppressed and conc. Of `OH^(-)`, furnished from `NH_(4)OH`, is such that only third roup basic radicals are precipitate.
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Knowledge Check

  • To avoid the precipitate of hydroxide of Ni^(2+),Co^(2+),Zn^(2+) and Mn^(2+) along with these of Fe^(3+),Al^(3+) and Cr^(3+) the third group solution should be

    A
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    A
    Heated with few drops of concentrated `HNO_3`
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    D
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