Analysis of carbonate mixtures by double indicator titrations?

Question

a. why is it necessary to use boiled and cooled distilled water in the dilution of a carbonate sample?

b. an aliquot of the diluted sample is titrated with some standard HCl until near the equivalence point, then it is boiled for 2-3 minutes. why should we boil it?

c.another aliquot us to be precipitated with 10% BaCl2 solution. what is the precipitation process' purpose?

d. any method to test the completeness of the precipitation of the sample with BaCl2?

thank you very much. all answers would be a very great help.

Answer 1

a & b.  Something gaseous is still dissolved in the distilled water (hint:  carbonic acid)

c.  (this is by definition)

d.  (higher Ksp)