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Which of the following concentration of ...

Which of the following concentration of `NH_(4)^(+)` will be sufficient to present the precipitation of `Mg(OH)_(2)` form a solution which is 0.01 M `MgCl_(2)`and `0.1 M NH_(3)(aq)`. Given that `K_(sp)Mg(OH)_(2)=2.5xx10^(-11)` and `K_(b)` for `NH_(3) = 2xx10^(-5)`.

Text Solution

Verified by Experts

`[OH^(-)] ` in `0.10 ` M `NH_(4)OH = sqrt((K_(b)C)) ` (Ostwald.s dilution law )
` sqrt(1.8 xx 10^(-5) xx 0.010 ) = 1.34 xx10^(-3)` M
` rArr [Mg^(2+)] = 0.01 M `
Ionic product ` = [ Mg^(2+)] [OH^(-)]^(2) = (0.01) xx (1.34 xx10^(-3))^(2)`
` = 1.8 xx10^(-8)gt K_(sp)`
As , Ionic products is greater than `K_(sp)` of ` Mg(OH)_(2)` hence precipitation should occur .
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