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 and D are inorganic salts. X is a solution of an inorganic compound. Carry out the following exercises on C, D and X. Record your observations and identity any gas(es) involved. State the conclusion drawn from the result or each test.
(a)(i) Add about 5 cm\(_3\) of distilled water to C in a test tube and shake thoroughly, Divide the resulting solution into two portions.
(ii) Put about 2cm\(^3\) of X into a separate test tube and add the first portion of solution in (a)(i) To the second portion of the resulting solution in (a)(i), add few drops of BaCl\(_{2(aq)}\) followed by excess dil. HCI.
(b) Add about 10 cm of distilled water to D in a boiling tube and shake thoroughly.
(i) To about 2 cm\(^3\) portion of the resulting solution in a test tube, add NaOH\(_{(aq)}\) in drops and then in excess
(ii) To another 2 cm\(^3\) portion of the resulting solution add few drops of K\(_2\)CrO\(_{4(aq)}\)
Explanation
| Test | Observation | Inference | |
| (a)(i) | C\(_{(s)}\) | C dissolved to give a colourless solution | |
| (ii) |
C\(_{(aq)}\) + X\(_{(aq)}\) |
X decolourized/turned colourless | C is a reducing agent |
| (iii) | C\(_{(aq)}\) + BaCl\(_{2(aq)}\) | White precipitate | SO\(_4^{2-}\), SO\(_3^{2-}\) or S\(^{2-}\) or SO\(_3^{2-}\) |
| + excess HCl\(_{(aq)}\) | precipitate dissolved/precipitate soluble | SO\(^{2-}_3\) confirmed | |
| (b) | D\(_{(s)}\) + distilled water | D dissolved to give a colourless solution | |
| (i) |
D\(_{(aq)}\) NaOH\(_{(aq)}\) in drops + excess NaOH |
White precipitate precipitate dissolved/precipitate |
Pb\(^{2+}\) or Ca\(^{2+}\) Pb\(^{2+}\) |
|
(ii) |
D\(_{(aq)}\) + K\(_2\)CrO\(_{(aq)}\) | Yellow precipitate | Pb\(^{2+}\) confirmed |