Credit will be given for strict adherence to instructions, for observations precisely recorded and for accurate inferences. All tests observations and inferences must be clearly entered in your answer book. in ink, at the time they are made.
C is a mixture of two inorganic compounds. Carry out the following exercises on C. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test.
(a) put all of C into a beaker and add about 10cm\(^3\) of distilled water. Stir thoroughly and filter. Keep both the residue and the filtrate
(b) Divide the filtrate into three portions.
(i) To the first portion, add sodium hydroxide solution in drops until ít is in excess.
(ii) To the second portion, add aqueous ammonia in drops until it is in excess.
(iii) To the third portion, add about 2cm\(^3\) of barium chloride solution, followed dilute hydrochloric acid in excess.
(c) Put the residue in a test tube and add about 2cm\(^3\) of dilute tetraoxosulphate (VI) acid. Shake the mixture and warm.
(i) Add aqueous ammonia in drops to the mixture from (c) (i) above until it is in excess.
Explanation
C is a mixture of CuO and ZnSO\(_4\)
|
Test |
Observation | Inference |
| (a) C + water filtered | Black residue, colourless filtrate | |
| (b)(i) Filtrate + NaOH\(_{(aq)}\) in drops , in excess |
White ppt. Precipitate dissolved |
Zn\(^{2+}\), Pb\(^{2+}\) or Al\(^{2+}\) |
| (ii) Filtrate + NH\(_{3(aq)}\) in drops, in excess |
White precipitate. Precipitate dissolved |
Zn\(^{2+}\) present/Confirmed |
|
(iii) Filtrate + BaCl\(_{2(aq)}\) + dil. HCl |
White ppt. Ppt. remained / insoluble |
CO\(^{2-}_3\) or SO\(^{2-}_4\) SO\(_4^{2-}\) present/confirmed |
| (c)(i) Residue + dil H\(_2\)SO\(_4\) | Residue dissolved (i) to from blue solution | Cu\(^{2+}\) likely |
|
(ii) Mixture of (c)(i) + NH\(_{3(aq)}\) in drops, in excess |
Light ble ppt ppt dissolved to give a deep blue solution |
Cu\(^{2+}\) confirmed |