[5 Mark Question Answer]

Question 15 Marks

Study the figure given alongside and answer the questions that follow :

(i) Name the experiment illustrated here.
(ii) Identify the gas Y.
(iii) What property of gas Y demonstrated by this experiment?
(iv) Explain the observations of the experiment.

Answer

(i) Fountain experiment.
(ii) The gas Y is HCl gas.
(iii) HCl gas is extremely soluble in water.
(iv) There is the formation of the fountain as water introduced from the dropper completely absorbs hydrogen chloride gas, thereby creating a very low pressure within the flask. Thus, to make up for this loss in pressure, blue litmus solution rises up the jet tube. The colour of litmus changes to red, because hydrogen chloride is an acidic gas.

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Question 25 Marks

The diagram shows an apparatus for the laboratory preparation of hydrogen chloride.
(i) Identify A and B.
(ii) Write the equation for the reaction.
(iii) How would you check whether or not the gas jar is filled with hydrogen chloride? Write the equation involved.
(iv) What does the method of collection tell you about the density of hydrogen chloride? Write the equation involved.

Answer

(i) A is conc. sulphuric acid
B is dry sodium chloride
(ii) $NaCl + H _2 SO _4$ (conc.) $\xrightarrow{<200^{\circ} C } NaHSO _4+ HCl$
(iii) By holding a glass rod dipped in ammonia solution near the mouth of the gas jar. If dense white fumes appear around the glass rod, it implies that the gas jar is filled. NH₃ + HCl → NH₄Cl
(iv) From this method of collection, we can safely conclude that HCl is heavier and hence denser than air.

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Chemistry [5 Mark Question Answer]

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