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40 ml of 0.1 M ammonia is mixed with 20 ml of 0.1 M HCl. What is the pH of the mixture ? (` pK_(b)` of ammonia solution is 4.74)A. 4.74B. 2.26C. 9.26D. `5.00` |
Answer» Correct Answer - C 40 ml of 0.1 M `NH_(3)` solution `= 40xx0.1` millimole = 4 millimoles `NH_(4)OH+HCl rarr NH_(4)Cl + H_(2)O` 2 millimole of HCl will neutralize 2 millimoles of `NH_(4)OH` to form 2 millimoles of `NH_(4)Cl`. `NH_(4)OH` left = 60 ml `:. [NH_(4)OH]=(2)/(60)M, [NH_(4)Cl]=(2)/(60)M` `pOH=pK_(b)+log .([NH_(4)Cl])/([NH_(4)OH])` `=4.74 + log .(2//60)/(2//60)=4.74` `:. pH=14-4.4.74=9.26` |
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