Question 2A
F is a mixture of two inorganic salts. Carry out the following on F.
Record your observations and identify any gas(es) evolved.
State the conclusions you draw from the result of each test.
- Put all of F in a beaker and add about 10 cm3 of distilled water, stir well and filter. Keep the filtrate and the residue.
- (i) To about 2 cm3 of the filtrate, add NaOH(aq) in drops and then in excess.
(ii) To another 2 cm3 portion of the solution, add NH3(aq) in drops and then in excess. - To another 2 cm3 portion of the solution, add a few drops of HNO3(aq) followed by few drops of AgNO3 (aq)
- (i) Put all the residue into a clean test – tube and add HNO3(aq)
(ii) To a portion of the solution from 2(d)(i) add NaOH(aq) in drops and then in excess. [ 22 marks]
Observation
This question tested the skills of qualitative analysis of samples of compounds and drawing correct inferences based on the properties of the compounds in different analytical reagents.
The performance of the candidates was fair.
In part (a), majority of the candidates were able to separate soluble salt from insoluble salt. But some of them lost marks to their inability to differentiate between a filtrate and a residue.
In part (c), majority of the candidates correctly used terms like soluble, insoluble and precipitate where necessary,
In part (d), some candidate wrote efflorescence instead of effervescence.
Expected answers include:
