QJEEM24Ch77b6: JEE Main 2024 Chemistry - Class 11 JEEM24Ch77b6 Solution: Given below are two statements : Statement (I) : Potassium…

Let's examine each statement one by one to choose the most appropriate answer :

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

This statement is correct. Potassium hydrogen phthalate (often abbreviated as KHP, with the chemical formula $$C_8{H}_{5}K{O}_4$$) is commonly used as a primary standard in titrations because it is pure, stable, non-hygroscopic, and has a high molar mass. It reacts with sodium hydroxide (NaOH) in a stoichiometric reaction, where one mole of KHP reacts with one mole of NaOH. The equation for the reaction is as follows :

$$C_8{H}_{5}K{O}_4+NaOH\to C_8{H}_{4}K{O}_{4}Na+H_{2}O$$

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

This statement is also correct. Phenolphthalein is a suitable indicator for the titration between KHP and NaOH. It changes color in the pH range of about 8.2 to 10, which is appropriate for the endpoint of a titration involving a weak acid (KHP) and a strong base (NaOH). In an acidic solution, phenolphthalein is colorless, but it turns pink in a basic solution, signaling the end of the titration when slight excess NaOH is present.

Given that both statements are correct, the most appropriate answer is :

• Option A : Both Statement I and Statement II are correct.