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.

Identify correct statements for primary standard substances

Q. 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.

A. D and E Only

B. A, B and E Only

C. A, B, C and E Only

D. A, B and C Only

Correct Answer: A, B and C Only

Explanation

A primary standard is a substance used to prepare a standard solution whose concentration is known accurately. Such substances must satisfy several strict conditions.

Statement A: Hydrated salts can be used as primary standards if their composition is definite and stable. Hence, this statement is correct.

Statement B: A primary standard should not react with air (no oxidation, no absorption of CO₂ or moisture). This ensures accurate mass measurement. Hence, this statement is correct.

Statement C: The reaction of a primary standard must be fast, complete and stoichiometric so that the equivalence point is well-defined. Hence, this statement is correct.

Statement D: A primary standard must be soluble in water to prepare standard solutions. Therefore, saying it should not be soluble is incorrect.

Statement E: A primary standard should have a high relative molar mass to minimize weighing error. Hence, this statement is incorrect.

Thus, the correct statements are:

A, B and C only

Explanation

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