Question 3A
(a) Consider the following diagram.
(i) Give the name of the experiment.
(ii) What does the experiment demonstrate?
(iii) Name one gas that could be used in place of HCl gas.
(iv) What colour could be observed in the flask during the spray of water?
(v) Could the gases used in the experiment be collected over water?
(vi) Explain briefly your answer in 3(a)(v).
(b) A solid substance U when strongly heated decomposes to give a white solid V and carbon (IV) oxide. When water is added to V, W is produced. W can be used to test for carbon (IV) oxide.
Identify U, V and W.
[9 marks]
Observation
In part (a), some candidates lost marks due to non famuliarization with the name
“fountain experience”. Equally, some candidates wrote the chemical formulae instead of
the name of the compound. However, the performance of the candidates was fair.
Expected answers include:
3(a)
(i) Fountain experiment
(ii) To demonstrate high solubility of hydrogen chloride gas
(iii) Ammonia
(iv) No colour/colourless
(v) No
(vi) The gases are highly soluble in water
(b)
U - CaCO3/calcium trioxocarbonate (IV)
V - CaO/calcium oxide
W - Ca(OH)2/calcium hydroxide