can anyone tell me that how do we confirm that molarity of any solution of ours is exactly what we have made after calculations? e.g. how can we confirm that a 5M EDTA solution is actually 5M or more or less?
The sodium salt of EDTA is water-soluble and being used in preparing a secondary standard solution of EDTA. The exact strength of EDTA can be worked out by performing a complexometric titration between a standard solution of CaCl2 and prepared EDTA solution at pH 12.0 using calcon indicator .
The standardization is needed as it is a secondary standard only and has less than 100% purity and also has associated water molecules in its chemical composition. Besides this, the strength of working solution is slightly altered due to recommended addition of a few grains of MgCl2 in EDTA solution for getting a quick colour change during titration of EDTA with primary standard (calcium chloride) solution in the presence of calcon indicator. The primary standard solution of calcium chloride is prepared by dissolving required amount of pure calcium carbonate in dilute HCl.
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