What are primary standard substance and examples

A primary standard substance is a chemical that is highly pure, stable, has a high molar mass, is non-hygroscopic (does not absorb moisture from the air), and can be weighed accurately to prepare a solution of precisely known concentration. These solutions are then used to standardize other solutions.

Examples of primary standard substances include: • Sodium carbonate ($\text{Na}_2CO_3$) for standardizing acids. • Potassium hydrogen phthalate ($\text{KHC}_8H_4O_4$, KHP) for standardizing bases. • Benzoic acid ($\text{C}_6H_5\text{COOH}$) for standardizing non-aqueous bases. • Potassium dichromate ($\text{K}_2Cr_2O_7$) for standardizing reducing agents.

Drop the next question.