Question 1B
E is a solution containing 5.99 g of HNO3 per dm3.
F is a solution containing 13.0 g of Na2CO3. YH2O per dm3.
- Put E into the burette and titrate it against 20.0 cm3 or 25.0 cm3 portions of F using methyl orange as indicator. Repeat the titration to obtain concordant titre values.
- From your results and the information provided, calculate the:
- concentration of E in mol dm-3;
- concentration of F in mol dm-3;
- concentration of F in g dm-3;
- percentage of water of crystallization in Na2CO3.yH2O.
Tabulate your results and calculate the average volume of E used.
Equation of the reaction is:
2HNO3(aq) + Na2CO3.yH2O 2NaNO3 (aq) + (y + 1)H2O(l) + CO2(g)
[H = 1,0, C = 12.0, O = 16.0, Na = 23.0]
[23 marks]
Observation
This question was on titration experiment. Majority of the candidates that responded this question performed above average.
In part (a), majority of the candidates obtained concordant values from the titration experiment;
In part (b), majority of the candidates calculated the concentration of E and F in mol dm-3. They also calculated the percentage of water of crystallization in Na2CO3.yH2O.
The expected answers include:
