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Primary Standard :
A primary standard is a reagent that is extremely pure, stable, has no waters of hydration, and has a high molecular weight.
Some primary standards for titration of acids:
sodium carbonate: Na2CO3, mol wt. = 105.99 g/mol
tris-(hydroxymethyl)aminomethane (TRIS or THAM): (CH2OH)3CNH2, mol wt. = 121.14 g/mol
Some primary standards for titration of bases:
potassium hydrogen phthalate (KHP): KHC8H4O4, mol wt. = 204.23 g/mol
potassium hydrogen iodate: KH(IO3)2, mol wt. = 389.92 g/mol
Some primary standards for redox titrations:
potassium dichromate: K2Cr2O7, mol wt. = 294.19 g/mol
A primary standard in chemistry is a reliable, readily quantified substance. Features of a primary standard include:
1. High purity
2. Stability (low reactivity)
3. Low hygroscopicity and efflorescence
4. High solubility (if used in titration)
5. High equivalent weight
Standard Solution :
Standard solution is a chemical term which describes a solution of known concentration. The concentration of the solution is normally expressed in units of moles per Litre (mol/L, often abbreviated to M for molarity). This unit, which stands for the moles of solute per litres of solution and concentration, is also known as molarity. Standard solutions are normally used in titrations to determine an unknown amount of a known substance such as a chemical compound.
To standardize a solution of acid you simple tritate it against a solution of alkali of known concentration. Once you have calculated this you can use it in turn as a standard solution, to find the concentration of a solution of alkali.
Standard solutions are also commonly used to determine the concentration of an analyte species. By comparing the absorbance a the sample solution at specific wavelength to a series of standard solutions at differing known concentrations of the analyte species, the concentration of the sample solution can be found via Beer's Law. Any form of spectroscopy can be used in this way so long as the analyte species has a substantial absorbance in spectra.
Source: Wiki answers.
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