Given below are two statements: Statement (I): Potassium hydrogen phthalate is a primary standard for standardisation of sodium hydroxide solution. Statement (II): In this titration phenolphthalein can be used as indicator. In the light of the above statements, choose the most appropriate answer from the options given below:

We analyze both statements about the standardisation of NaOH using potassium hydrogen phthalate (KHP).

Statement I: Potassium hydrogen phthalate (KHP) is a primary standard for standardisation of sodium hydroxide solution.

KHP is indeed a well-known primary standard. It is a stable, pure, non-hygroscopic solid with a high molecular weight, making it ideal for accurately standardizing NaOH solutions. Statement I is CORRECT.

Statement II: In this titration, phenolphthalein can be used as indicator.

KHP is a weak acid (monoprotic, from phthalic acid). The titration of a weak acid (KHP) with a strong base (NaOH) has an equivalence point in the basic pH range (around pH 8-10). Phenolphthalein changes colour in the pH range 8.2-10.0, which coincides with the equivalence point. Statement II is CORRECT.

Both statements are correct. The answer is Option A) Both Statement I and Statement II are correct.