Identify the correct statements:
A. Hydrated salts can be used as primary standard.
B. Primary standard should not undergo any reaction with air.
C. Reactions of primary standard with another substance should be instantaneous and stoichiometric.
D. Primary standard should not be soluble in water.
E. Primary standard should have low relative molar mass.
Choose the correct answer from the options given below:
A. Hydrated salts can be used as primary standard.
B. Primary standard should not undergo any reaction with air.
C. Reactions of primary standard with another substance should be instantaneous and stoichiometric.
D. Primary standard should not be soluble in water.
E. Primary standard should have low relative molar mass.
Choose the correct answer from the options given below:
- (A)A, B, C and E only
- (B)A, B, and C only✓ Correct
- (C)A, B and E only
- (D)D and E only
Answer: (B)
Solution
A primary standard must be stable in air so that its composition does not drift during weighing, which makes statement B valid, and its reaction with the titrant must be rapid, complete and strictly stoichiometric, which makes statement C valid. Several hydrated salts, such as oxalic acid dihydrate and borax, serve as excellent primary standards, so statement A is also valid. A primary standard must dissolve readily to prepare its solution, so statement D is wrong, and it should have a high rather than a low molar mass so that weighing errors are minimised, so statement E is wrong. The correct statements are A, B and C only.
JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Single correct option