C is a mixture of an organic and an inorganic salt. The test recorded in the table below were performed as indicated,
(a)Copy and complete the table as appropriate.
| Test | Observation | Inference |
| (i) C + water mixed thoroughly and filtered | Partially soluble, colourless filtrate, white residue | |
|
(ii) Portion of filtrate from (i) + NH\(_{3(aq)}\) in drops, then in excess |
White precipitate which dissolves in excess to give a colourless solution | |
| (iii) Portion of filtrate from (i) + NH\(_3\) in drops, then in excess | White precipitate insoluble in excess | |
| (iv) Portion of filtrate from (i) + conc. HCl + heat | White precipitate which dissolves on warming and reappears on cooling | |
| (v) Portion of filtrate from (i) + conc. H\(_2\)SO\(_4\) + gentle warming | Brown fumes produced on warming | |
| (vi) Residue from (i) + iodine solution | Blue-black colouration | |
| (vii) Residue from (i) + Fehling’s solution + heat | ||
| (vii) Residue from (i) + dil HCl solution + heat + Fehling’s solution |
(b) From the information provided and your inference, identify the compounds of C
(c) Describe the action of heat on a solid sample of the inorganic component Write an equation for the reaction.
(d) State what would be observed if an aqueous suspension of the organic component were heated to boiling
Explanation
| Test | Observation | Inference |
| (i) C + water mixed thoroughly and filtered | Partially soluble, colourless filtrate, white residue | One soluble and the other is not |
|
(ii) Portion of filtrate from (i) + NH\(_{3(aq)}\) in drops, then in excess |
White precipitate which dissolves in excess to give a colourless solution | Zn\(^{2+}\), pb\(^{2+}\) or Al\(^{3+}\) present |
| (iii) Portion of filtrate from (i) _ NH\(_3\) in drops, then in excess | White precipitate insoluble in excess | Pb\(^{2+}\) or Al\(^{3+}\) present |
| (iv) Portion of filtrate from (i) + conc. HCl + heat | White precipitate which dissolves on warming and reappears on cooling | Pb\(^{2+}\) confirmed |
| (v) Portion of filtrate from (i) + conc. H\(_2\)SO\(_4\) + gentle warming | Brown fumes produced on warming |
fumes of NO\(_2\); NO\(_3\) + present |
| (vi) Residue from (i) + iodine solution | Blue-black colouration |
Residue is starch |
| (vii) Residue from (i) + Fehling's solution + heat | No precipitate or any visible reaction |
Starch is non-reducing or reducing sugar absent |
| (vii) Residue from (i) + dil HCl solution + heat + Fehling's solution | Brick - red precipitate | Starch has been hydrolysed to reducing sugar |
(b) C is a mixture and lead II trioxonitrate (V) is one
(c) The precipitate (makes a cracking sound) produced copious brown fumes of Nitrogen (IV) oxide on heating. The residue turns red when hot and yellow when cold, lead (II) oxide and a gas that relights a glowing splint evolved. Pb(NO\(_3\))\(_2\) \(\to\) PbO + 2NO\(_2\) + O\(_2\)
(d) It will give a colloidal solution (or jelly-like solution)