Question

Which of the following statement is incorrect? 

(1) KMnO₄ and NaOH can be used as secondary standard 

(2) Primary standard should not undergo change in air 

(3) Reaction of primary standard with another substance should not be instantaneous 

(4) Primary standard should be soluble in H₂O

Answer 1

Correct option is (3) Reaction of primary standard with another substance should not be instantaneous 

Reaction of primary standard with another substance should be instantaneous and stoichiometric.