n the food additives quality control laboratory, a solution was prepared by dissolving 4.1000 g of a sample (containing a mixture of carbonate of sodium and sodium bicarbonate) in water to 200.00 mL of solution. From this solution were two aliquots of 10.00 mL were taken. The 1st aliquot was titrated using 0.10 mol/L HCl (Fc= 0.9600), in the presence of phenolphthalein, and 10.20 mL of this acid were spent. the 2nd. aliquot was titrated with the same acid, in the presence of methyl orange, using 29.50 mL.

a) Calculate the levels (in % w/v) of carbonate (CO3^2-) and bicarbonate (HCO3-) present in this sample.

b) Why was methyl orange used in the second titration but not used in the second titration? first degree?