# Question #bab14

May 22, 2015

A primary standard is a reagent that is stable, is extremely pure, has no water of hydration, and has a high molar mass.

Some primary standards are:

• sodium carbonate, ${\text{Na"_2"CO}}_{3}$, for the titration of acids
• potassium hydrogen phthalate (KHP), ${\text{KHC"_8"H"_4"O}}_{4}$, for the titration of bases
• potassium dichromate, ${\text{K"_2"Cr"_2"O}}_{7}$, for redox titrations
• sodium oxalate, ${\text{Na"_2"C"_2"O}}_{4}$, for redox titrations

A standard solution is a solution with an accurately and precisely known concentration.

It is prepared by using a primary standard.

It is often used to determine the concentrations of other substances by titration.

For example, you might prepare a standard solution of KHP to determine the concentration of a solution of $\text{NaOH}$.