Question

what is the difference between a primary and a secondary standard ? Give example of each

Answer 1

The term 'primary and secondary standard' term used in analytical chemistry . But the term primary standard used to those reagent which are significantly extra pure, non hygroscopic , having high molecular weight and low reactivity. Once a primary standard solution is made, then standardity remain unchanged for long periods. Some examples are K₂Cr₂O_{7 ,} Na₂C₂O₄ etc.

Whereas, secondary standard reagents are those which when made for solution, the standardity may change occasionally due to hygroscopicity, low molecular weight and impurities present in the reagent . Example : NaOH.