Why is the carbonate solution boiled before titrating?

Answer 1

You should be more explicit about your question; I assume you are titrating carbonate to the methyl red or methyl orange end point. The reason you boil the solution is expel the CO2 that is dissolved in the solution. During the titration you have
CO3^2- + 2H^+ ==> H2CO3 ==> H2O + CO2 and this is an equilibrium reaction there is still a little of the H2CO3 present. By expelling all of the CO2, all of the H2CO3 can be titrated.