Identify the incorrect statements regarding primary standard of titrimetric analysis. (A) It should be purely available…

Properties of a primary standard: A primary standard must be:

1. Available in high purity
2. Stable in air (not hygroscopic, not oxidised)
3. High molar mass (to reduce weighing errors)
4. Readily soluble in the solvent
5. React stoichiometrically and completely

Step 1 — Evaluate each statement:

(A) "Available in dry form" — ✓ Correct property of a primary standard

(B) "Should not undergo chemical change in air" — ✓ Correct (must be stable)

(C) "Should be hygroscopic" — ✗ Incorrect: A primary standard must NOT be hygroscopic (absorbing moisture would change its mass and concentration). This is an incorrect statement.

(D) "Should be readily soluble in water" — ✓ Correct property

(E) "$\mathrm{KMnO_4}$ & NaOH can be used as primary standard" — ✗ Incorrect:

• $\mathrm{KMnO_4}$ is not a primary standard (it oxidises organic matter, difficult to obtain pure)
• NaOH is not a primary standard (it is hygroscopic and absorbs $\mathrm{CO_2}$ from air)

Incorrect statements: C and E

Answer: Option (2) — (C) and (E) only