Question

Assertion $\left(A\right):$ A solution containing a mixture of Acetic Acid and Sodium Acetate maintains a constant value of pH on addition of small amount of acid or alkali.

Reason $\left(R\right):$ A solution containing a mixture of Acetic Acid and Sodium Acetate acts as a buffer solution around $pH4.75$

• A. $A$ is false but $R$ is true.
• B. Both $A$ and $R$ are true but R is not the correct explanation of $A.$
• C. Both $A$ and $R$ are true and $R$ is the correct explanation of $A.$
• D. $A$ is true but $R$ is false.

Answer 1

The correct option is C

Both $A$ and $R$ are true and $R$ is the correct explanation of $A.$

Analyzing the assertion

Given solution of $C{H}_{3}COOH$ and $C{H}_{3}COONa$ maintain constant value of $pH$ on addition of small amount of acid or alkali. Yes, it is correct

statement

Analyzing the reason

Since, it is an acidic buffer, because it is prepared from weak acid (i.e. acetic acid) and its salt with strong base (i.e. Sodium Acetate).

Buffer solution resists change in $pH$ value.

Since this is acidic buffer,.

So, the buffer range will be observed at $pH$ of around

$pH\approx pKa$ $(pKa=4.75,\text{for acetic acid})$

So, the statement given in reason is correct and it explain the assertion too. Hence,

$\therefore$ Both assertion and reason are true and reason is the correct explanation of assertion.

Therefore, correct answer is option $\left(A\right).$