Question

12 g of $C{H}_{3}COOH$ and 4 g of NaOH are mixed and diluted to 1 litre solution. If $P^{Ka}$ of $C{H}_{3}COOH$ is 4.8, then the $p^H$ of the solution is:

• A. 4.8
• B. 5
• C. 5.699
• D. 5.301

Answer 1

The correct option is A 4.8

12 g of $C{H}_{3}COOH$ and 4 g of NaOH corresponds to 0.2 moles of $C{H}_{3}COOH$ and 0.1 mole of NaOH respectively.
0.1 mole of $C{H}_{3}COOH$ will react with 0.1 mole of NaOH to form 0.1 mole of salt sodium acetate.
0.1 mole of $C{H}_{3}COOH$ will remain unreacted.
Hence, $\left[Acid\right]=\left[Salt\right]=0.1$ M
The expression for the pH of the acidic buffer solution is as given below.
$pH=p{K}_a+log\frac{\left[Salt\right]}{\left[Acid\right]}$
When, $\left[Acid\right]=\left[Salt\right]$, $pH=p{K}_a$
But $p{K}_a=4.8$
Hence, $pH=4.8$.