Question 1
D was prepared by diluting 35.0 cm3 of saturated solution of sodium trioxocarbonate ( IV ) at 250 C to 1 dm3.
Solution E is 0.0905 moldm-3 trioxonitrate ( V ) acid.
Titration of 20.0 cm3 portions of D with E using methyl orange as indicator gave the following results:
- (i) Copy and complete the table.
(ii) Calculate the average volume of E used.
Equation of reaction:
- From the information provided, calculate the;
(i) concentration of D in moldm-3;
(ii) solubility of Na2CO3 in D moldm-3 at 250C;
(iii) volume of the saturated solution that should be evaporated to yield 25g of Na2CO3;
(iv) mass of CO2 released when 1 dm3 of the saturated solution reacted.
[ Na = 23.0; C = 12.0; O = 16.0; H = 1.0; N = 14.0 ] [21 marks]
Observation
It was a popular question among the candidates. Majority of them were familiar with the question. In part ( a ), few candidates could not subtract the initial reading from the final reading on the titration table. In part ( b ), majority of the candidates performed very well, but few of them could not determine the mole ratio.
The expected answers include:
-
-
(i)
(ii)
(iii)
(iv)