Question

Given below are two statements.
Statement I: In the titration between strong acid and weak base methyl orange is suitable as an indicator.
Statement II : For titration of acetic acid with $NaOH$ phenolphthalein is not a suitable indicator.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Statement I is false but Statement II is true
• B. Statement I is true but Statement II is false
• C. Both Statement I and Statement II are true
• D. Both Statement I and Statement II are false

Answer 1

Answer: (B)

Titration curve for strong acid and weak base initially a buffer of weak base and conjugate acid is :

Formed, thus $pH$ falls slowly and after equivalence point, so the $pH$ falls sharply so methyl arrange, having $pH$ range of $3.2$ to $4.4$ will weak as indicator. So statement-I is correct.

Titration curve for weak acid and strong base $( NaOH )$
Initially weak acid will form a buffer so $pH$ increases slowly but after equivalence point. it rises sharply covering range of phenolphthalein so it will be suitable indicator so statement-II is false.