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To prepare a buffer of pH 8.26, amount o...

To prepare a buffer of pH `8.26`, amount of `(NH_(4))_(2)SO_(4)` to be added into 500mL of `0.01M NH_(4)OH` solution `[pK_(a)(NH_(4)^(+))=9.26]` is:

A

0.05 mol

B

0.025 mol

C

0.10 mol

D

0.005 mol.

Text Solution

Verified by Experts

The correct Answer is:
B
Let `(NH_(4))_(2)SO_(4)` to be added to 500mL solution
`= x mol`
`:. [NH_(4)^(+)]=4xM`
`pH=8.26`
`pOH=14-8.26=5.74`
`pK_(b)=14-9.26=4.74`
`pOH=pK_(b)+log.([NH_(4)^(+)])/([NH_(4)OH])`
`5.74 =4.74 +log.(4x)/(0.01)`
`log 4xx\ 10^(2)=1`
`4 x xx 10^(2)=10`
`x=(1)/(40)mol =0.025 mol`
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Amount of (NH_(4))_(2)SO_(4) which must be added to 50mL of 0.2 M NH_(4)OH solution to yield a solution of pH 9.26 is ( pK_(b) of NH_(4)OH=4.74 )

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DINESH PUBLICATION-IONIC EQUILIBRIUM -MULTIPLE CHOICE QUESTIONS
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