Question 2B
H is a simple salt. Carry out the following exercises on H. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.
(a)
(i) Add about 10cm3 distilled water to H and shake thoroughly. Perform the following tests on portions of the resulting solution.
(ii) Test the solution with litmus paper.
(iii) To about 2cm3 portion of the solution, add NaOH(aq) in drops and then in excess.
Warm the resulting mixture gently.
(iv) To another 2 cm3portion of the solution, add dil. HCl.
(v)
I. Name the salt present in H.
II. Write its formula. [17 marks]
Observation
This question was attempted by majority of the candidates and the performance was fair. Some candidates carried out wrong test, they carried out analysis on solid instead of using the solution of the solid.
Expected answers include:
|
Test |
Observation |
Inference |
|
H+ distilled water |
Yellow solution formed/ solution remains unchanged |
|
(ii) |
H(aq) + litmus paper |
Turned red litmus paper |
Solution is basic/ alkaline |
(iii) |
H(aq) + NaOH(aq) in drops then in excess |
No visible reaction/no gas evolved |
NH3 gas evolved |
(iv) |
H(aq) + dilHCl |
Colourless gas evolved which smell like a rotten egg turned lead (II) ethanoate paper silvery brown/black |
Gas is H2S |
(v)
(i) Ammonia Sulphide
(ii) (NH4)2S