QJEEM24Ch3348: JEE Main 2024 Chemistry - Class 11 JEEM24Ch3348 Solution: Identify the incorrect statements regarding primary standard of …

Let's evaluate each statement to identify the incorrect ones regarding the primary standard in titrimetric analysis:

(A) It should be purely available in dry form.

This statement is generally correct. A primary standard should be pure and available in a stable, dry form to ensure accurate weight measurements.

(B) It should not undergo chemical change in air.

This statement is also correct. A primary standard should be stable in air and not react with components of the atmosphere such as oxygen or carbon dioxide.

(C) It should be hygroscopic and should react with another chemical instantaneously and stoichiometrically.

This statement is incorrect. A primary standard should not be hygroscopic (it should not absorb moisture from the air) because hygroscopic substances cannot maintain a constant weight. The part about reacting stoichiometrically and instantaneously is generally correct, but being hygroscopic disqualifies a substance from being a primary standard.

(D) It should be readily soluble in water.

This statement is correct. A primary standard should be soluble in water to ensure that it can be dissolved to make a standard solution for titration.

(E) $${\mathrm{KMnO}}_4$$ & $$\mathrm{NaOH}$$ can be used as primary standard.

This statement is incorrect. Both $${\mathrm{KMnO}}_4$$ (potassium permanganate) and $$\mathrm{NaOH}$$ (sodium hydroxide) are not suitable as primary standards. $${\mathrm{KMnO}}_4$$ is unstable and can decompose, while $$\mathrm{NaOH}$$ is hygroscopic, which makes precise weight measurements difficult.

Hence, the correct answer is:

Option A

(C) and (E) only