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
A, B, C and E only
- B
A, B, and C only
- C
A, B and E only
- D
D and E only
A primary standard must be of high purity, stable in air, react stoichiometrically and instantaneously with the titrant, and be soluble in the solvent used (usually water) so that a standard solution can be made.
Statement A: Some hydrated salts (e.g., oxalic acid dihydrate, sodium oxalate, etc.) are valid primary standards — correct.
Statement B: Must not react with air (or absorb /moisture) — correct.
Statement C: Reaction should be instantaneous and stoichiometric — correct.
Statement D: Must be soluble, not insoluble — wrong.
Statement E: A high (not low) molar mass is preferred to reduce weighing errors — wrong.
So A, B and C are correct.
Practice more Chemistry
Concept-wise practice with instant solutions on Fundamenthol.
Start practicing →