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Please,please help me The solubility products of Al(OH)3and Zn(OH)2are 8.5x10-23and 1.8x10-14respectively. IfNH4OH is added to a solution containing Al3+and Zn2+ions, then substance precipitated first is

The solubility products of Al(OH)and Zn(OH)2 are 8.5x10-23 and 1.8x10-14 respectively. If NH4OH is added to a solution containing Al3+ and Zn2+ ions, then substance precipitated first is

  • Option 1)

    Al(OH)3

  • Option 2)

    Zn(OH)2

  • Option 3)

    Both together 

  • Option 4)

    None of these 

 
Answers (1)
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As we learned in concept

Solubility product constant -

e.g.

BaSO_{4}\rightleftharpoons Ba^{2+}(aq)+SO_{4}^{2-}(aq)


K=\frac{[Ba^{2+}]\:[SO_{4}^{2-}]}{[BaSO_{4}]}

- wherein

For a pure solid substance the concentration remain constant

\therefore \:K_{sp}=K[BaSO_{4}]
 

               =[Ba^{2+}]\:[SO_{4}^{2-}]
 

    K_{sp}=solubility\:product

 

 Given solubility products

 Al(OH)_3: 8.5\times 10^{-23}

Zn(OH)_2: 1.8\times 10^{-14}

Since solubility of Al(OH)_3 is lower than Zn(OH)_2  and 

K_{sp}[Zn(OH)_2]=[Zn^{2+}][OH^-]^2

\therefore Al(OH)_3 will be participated first.


Option 1)

Al(OH)3

Correct

Option 2)

Zn(OH)2

Incorrect

Option 3)

Both together 

Incorrect

Option 4)

None of these 

Incorrect

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