Question

What is a primary standard?
Why is NaOH not a primary standard?

Answer 1

Dear Student

A primary standard is a reagent which can be weighed easily, and which is so pure that its weight is truly representative of the number of moles of substance contained. Concentration of primary standard solution does not change with time.

NaOH is not suitable for use as a primary standard because it readily absorb moisture, H2​O, from the atmosphere and also absorb carbon dioxide from the atmosphere.

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