Question

Which is the best choice for weak base-strong acid titration?
(a) methyl red
(b) litmus
(c) phenol red
(d) phenolphthalein

Answer 1

Hint:The titration of the weak base and strong acid results in the formation of the solution which is acidic in nature and for such reactions red indicator which consists of the methyl group is used. Now you can easily identify that indicator.

Complete step-by-step answer:First of let’s discuss what is a strong acid and base. Strong acids are those acids which can easily give the proton whereas on the other hand, weak bases are those bases which cannot easily give the hydroxyl ions.
When the strong acid reacts with the weak base, it results in the formation of the water and the salt i.e. the strong acid neutralizes the weak base.
Now considering the statement as;
When the strong acid will react with the weak base , it forms an acidic solution i.e. the solution will have the pH less than seven.
In such titrations (strong acid-weak base); methyl red is used as an indicator which changes the acidic solution to red in color which works in the range of pH from four to seven.
Thus, the best choice for weak base-strong acid titration is methyl red.

So, option (a) is correct.

Note:The reactions in which the strong acid reacts with strong base or strong base reacts with weak acid or strong acid reacts with the weak base or weak acid reacts with the weak base resulting in the formation of the salt and water are known as the neutralization reactions.