Equilibrium - Result Question 91

####95. Solution of 0.1NNH4OH and 0.1NNH4Cl has pH 9.25. Then find out pKb of NH4OH [2002]

(a) 9.25

(b) 4.75

(c) 3.75

(d) 8.25

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Solution:

(b) pOH=pKb+log[ Salt ][ Base ]

or pKb=pOHlog [salt]  [Base] 

but pOH+pH=14 or pOH=14pH

14pHlog[ Salt ][ Base ]=pKb

149.25log0.10.1=pKb

149.250=pKb

pKb=4.75



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