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A 0.4863-g sample of primary standard sodium carbonate (Na2CO3, fw 105.988) was

ID: 774723 • Letter: A

Question

A 0.4863-g sample of primary standard sodium carbonate (Na2CO3, fw 105.988) was treated with 40.00-mL of a dilute perchloric acid (HClO4, fw 100.458) solution. The solution of boiled to remove CO2, following which the excess HClO4 was back-titrated with 8.72-mL of 0.3045 M NaOH using bromocresol green as an indicator.


a) Write balanced chemical equations for the reaction of "soudium carbonate with perchloric acid" and "sodium hydroxide with perchloic acid".


b) What is the concentration of the perchloric acid solution?

Explanation / Answer

HClO4 + Na2CO3 ------->2 NaClO4 + H2O + CO2

HClO4 + NaOH --------------> NaClO4 + H2O