(a)
A 0.19 g sample of sodium carbonate (Na2CO3) and sodium bicarbonate
(Na4CO3) mixture was dissolved in 25 mL of water. The sample solution was
titrated with 30 mL 0.10 M hydrochloric acid (HCI) to reach the end point
using methyl red as indicator. Calculate the number of moles of HCI used for
the titration.(5 marks)
(b)A second 0. 19 g sample was dissolved in 25 mL of water and 20 mL 0.2 M
sodium hydroxide solution was added. Then excess amount of barium
chloride (BaCl2) was added to precipitate the carbonate. The remaining
solution was titrated against 0. 10 M HCI solution. It required 30 mL of HCl
solution to reach the end point using phthenolpthalein as indicator. Calculate
the weight % of Na2CO3 and NaHCO3, in the mixture.
(10 marks)
(c)What is the pH of the titration mixture in part B at its end point. (5 marks)