Question

What happens to the ${\text{pH}}$ of the solution when an acidic solution is titrated with drops of base?
A. Increase
B. Decrease
C. Remain the same
D. Approach zero
E. None of the above

Answer 1

At Equivalence point the moles of acid are neutralized with the moles of base. With the increase in the amount of base required to neutralize the acid the hydrogen ion concentration of the acid decreases

Complete step by step answer:
The quantitative analysis for the determination of concentration of the given acid or base by neutralizing it with the standard solution of base or acid having known concentration is called acid base titration.
There are 4 types of acid base titrations
Strong acid-strong base, weak acid- strong base, strong base-strong acid, weak base-strong acid.
On a titration curve for an acidic solution ${\text{pH}}$ is plotted against the volume of base progressively added. With the addition of base ${\text{pH}}$ slowly rises towards the equivalence point. This is the point where precisely enough base is added to neutralize the exact amount of acid in the solution. In an acid base titration the visual indication of equivalence point is possible by the addition of indicator to the analyte solution. The point at which the indicator changes its colour is called the end point. When we neutralize a strong acid with a strong base the equivalence point will be 7, if either or both are weak then this number will vary. Thus when an acidic solution is titrated against the base, the acid strength decreases, the concentration of hydrogen ion thus decreases which results in the increase in ${\text{pH}}$.

So, the correct answer is Option A .

Note: Indicators are selected based on the ${\text{pH}}$ change near the equivalence point
The indicators generally used for acid base titrations are
For strong acid strong base titrations methyl orange, Phenolphthalein indicators are used
For weak acid strong base titrations phenolphthalein, Thymolphthalein,
For strong acid weak base methyl orange, methyl red
And for weak acid weak base titrations the indicators used are mixed indicators. When weak acid and weak base is involved in the titration, the ${\text{pH}}$ range is very narrow at the equivalence point a sharp colour change is required to identify the end point so mixed indicators are used

Acid base titration is used to determine the concentration of unknown acid or unknown base by titrating it against the standard solution of base or acid of known concentration.