Question

Which of the following plot represents the graph of $pH$ against volume of alkali added in the titration of $NaOH$ and $HCl$

• A.
• B.
• C. None of the above
• D.

Answer 1

The correct option is D

While adding alkali to acid, there occurs a change in $pH$
and the acidity of acid becomes decreasing and the basicity will start to increase. But there is no sudden increase in the $pH$
Hence, option (A) is incorrect.
Here, the base is added to the acid solution. Hence, $pH$
of the solution is low at the initial stage. But, in this graph, the plot of $pH$
starts from its higher range. Hence, option (B) is incorrect.
When sodium hydroxide is added to hydrochloric acid, $pH$
of the solution remains the same at the initial stage. After that it suddenly increases $pH$
. Then it became almost the same. After that there is no change in the $pH$
. Therefore, the graph of $pH$ against volume of alkali added in the titration of $NaOH$and $HCl$ is