(a) Suggest how the following liquid reagents can be suitably stored in the laboratory
(i) X which fumes in moist air;
(ii) Y which is slowly decomposed by sunlight in ordinary reagent bottles.
(b) State what is observed when aqueous ammonia is added to:
(i) litmus paper;
(ii) Pb(NO\(_3\))\(_2\) solution in drops until in excess
(iii) freshly precipitated AgCI in excess.
(c) A salt sample was suspected to be either Na\(_2\)CO\(_2\) or NaHCO\(_3\). A student who was required to identify it tested a portion for solubility in water and then for effect on litmus paper.
(i) What was observed in each case?
(ii) Give the reason why the student's procedure was unsuitable
(iii) Describe briefly how you would have identified the salt.
(a)(i) X is better stored in fume cupboard/chamber
(ii) Y should be stored in coloured bottles or dark cupboard
(b)(i) it turns red litmus paper to blue, but no action on blue litmus paper.
(ii) A white gelatinous precipitate is formed and it will be insoluble in ammonium solution.
(iii) A white freshly precipitate of the freshly prepared of AgCl will dissolve.
(c)(i) Na\(_2\)CO\(_3\) is neutral to litmus but NaHCO\(_{3(aq)}\) Will turn blue litmus to red.
(ii) The procedure was not suitable because the two substances are soluble in water and hence they cannot be detected using solubility.
(iii) Na\(_2\)CO\(_3\) and NaHCO\(_3\) should be separately heated strongly. NaCO\(_3\) is stable under heat but NaHCO\(_3\) vill decompose given off H\(_2\)O and CO\(_2\) and leaving Na\(_2\)CO\(_3\). The water and CO\(_2\) can be tested to confirm which is which.
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