Credit will be given for strict adherence to the 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 contains two cations and two anions. Perform the following exercises on C. Record your observations and identify any gas (es) evolved. State the conclusion you draw from the result of each test.
(a) Dissolve all of C in about 10 cm\(^3\) of distilled water. Stir the resulting solution thoroughly.
(i) To about 2 cm\(^3\) of the solution, add few drops of AgNO\(_3\) solution, followed by HNO\(_{3(aq)}\). To the mixture, add excess NH\(_{3(aq)}\)
(ii) To another 2 cm\(^3\) portion of the solution, add dil. HCl followed by BaCl\(_2\) solution.
(iii) To another 2 cm\(^3\) portion of the solution, add NaOH\(_{3(aq)}\) dropwise and then in excess. Warm the mixture.
(iv) To another 2 cm\(^3\) portion of the solution, add NH\(_{3(aq)}\) dropwise and then in excess.
Explanation
| TEST | OBSERVATION | INFERENCE | |
| (i) |
C(\(_{aq}\)) + AgNO\(_3\) + HNO\(_{3(aq)}\) + NH\(_{3(aq)}\) excess |
White precipitate formed precipitate insoluble Precipitate soluble/dissolved |
Cl\(^-\) or S\(^{2-}\) or CO\(_3^{2-}\) Cl\(^-\) present |
| (ii) |
C\(_{(aq)}\) + HCl\(_{(aq)}\) + BaCl\(_{2(aq)}\) |
No visible reaction/no gas evolved White (chalky) precipitate formed |
SO\(_4^{2-}\) present |
| (iii) |
C\(_{(aq)}\) + NaOH\(_{(aq)}\) in drops in excess Mixed warmed
|
White gelatinous precipitate White precipitate dissolved/soluble Colourless gas evolved pungent/choking/irritating smell evolved Gas turns red litmus paper blue or forms dense white fumes with conc. HCl |
Zn\(^{2+}\) or Al\(^{3+}\) suspected Zn\(^{2+}\) or Al\(^{3+}\) suspected
NH\(_3\) gas evolved NH\(_4^+\) present |
| (iv) |
C\(_{(aq)}\) + NH\(_{3(aq)}\) in drops in excess |
White gelatinous precipitate Precipitate dissolved/soluble |
Zn\(^{2+}\) or Al\(^{3+}\) is suspected Zn\(^{2+}\) present |