Answer
The most appropriate drawing of that curve is in second drawing.
$- (ii)$
Work Step by Step
- The original solution is made of a strong base.
Therefore, its pH should be high (greater than 7).
- Since we are adding a strong acid:
The hydronium ion concentration should raise, decreasing the pH.
The only drawing where the pH is decreasing with the addition of the compound is the number $(ii)$
