Credit will be given for strict adherence to the instructions, for observations precisely record 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 salts. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion drawn from the result of each fest
(a) Put all of C into a boiling tube and add about 5cm\(^3\) of distilled water. Stir thoroughly and filter. Keep both the residue and the filtrate.
(b) To about 2 cm\(^3\) of the filtrate, add few drops of Pb(NO\(_3\))\(_{(aq)}\). Boil the mixture and then allow to cool.
(c)(i) Put the residue in a test tube and add dilute HNO\(_{3}\). Shake the mixture and divide the solution into two portions
(ii) to the first portion from (c)(i), add NaOH\(_{(aq)}\) in drops acid then in excess.
(iii) To the second portion from (c)(ii), add aqueous ammonia in drops and then in excess
Explanation
| TEST | OBSERVATION | INFERENCE |
| (a) C + water, mixture stirred and filtered | partly dissolved, colorless filtrate. White residue | C contains soluble and insoluble salts |
|
(b) Filterate + Pb(NO\(_3\))\(_2\) Boiled then cooled |
White precipitate formed Precipitate dissolved Precipitate reappears |
Cl\(^-\), or SO\(_4^{2-}\) or CO\(_3^{2-}\)
Cl\(^-\) confirmed |
| (c)(i) Residue + dil. HNO\(_3\) | Effervescence or bubbles or gas evolved. Colourless, odourless gas which turns lime water milky | CO\(_2\) gas evolved from CO\(_3^{2-}\) |
|
(ii) Solution from (i)+ NaOH\(_{(aq)}\) in drops then in excess |
White gelatinous precipitate formed, precipitate dissolves |
Zn\(^{2+}\) or Al\(^{3+}\) Zn\(^{2+}\) or Al\(^{3+}\) |
|
(iii) Solution from (i)+ NH\(_{3(aq)}\) in drops then in excess |
White gelatinous precipitate formed, precipitate dissolves |
Zn\(^{2+}\) or Al\(^{3+}\) Zn\(^{2+}\) confirmed |