Question 1B
B is a solution of hydrochloric acid.
D is a solution containing 2.45 g of anhydrous sodium trioxocarbonate (IV) in 250 cm3 of solution.
- Put B into the burette and titrate it against 20.0 cm3 or 25 cm3 portion of D using methyl orange as indicator. Repeat the titration to obtain consistent titre values.
Tabulate your results and calculate the average volume of B used.
The equation for the reaction is:
-
From your results and the information provided, calculate the :
(i) concentration of D in moldm-3;
(ii) concentration of B in moldm-3
(iii) concentration of B in gdm-3
(iv) volume of the gas evolved in the reaction at s.t.p.
[H = 1.0; C = 12.0; Na = 23.0; Cl = 35.5; molar volume = 22.4 dm3 mol-1] [ 21 marks ]
Observation
In part (a), majority of the candidates presented their titration results in correct format. However, some candidates titer values were not concordant. In part (b), majority of the candidates calculated the concentrations of substances in moldm-3 and gdm-3 respectively. However, some of them could not calculate the volume of the gas evolved in the reaction at s.t.p.
Expected answers include:
(a)Two consistent/ concordant titres
Averaging
(i) 
