1.

The pH of a solution containing `0.20M CH_(3)COOH` and `0.30M CH_(3)COONa` isA. `2.89`B. `4.92`C. `5.04`D. `3.89`

Answer» Correct Answer - B
Since we are dealing with a mixture of a weak acid and its salt with a strong base, we can calculate the pH of the solution by using the Henderson-Hasselbalch equation:
`pH=pK_(a)+"log"(C_("salt"))/(C_("acid"))`
In this case, we need to calculate `pK_(a)` and the acid first:
`pK_(a)= -logK_(a)`
`= -log(1.8xx10^(-5))`
`=4.74`
Now, we substitute the value of `pK_(a)` and concentrations of the acid and its salt:
`pH=pK_(a)+"log"(C_("salt"))/(C_("acid"))`
`=4.74+"log"(0.30)/(0.20)`
`=4.74+log(1.5)`
`=4.92`


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