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.
H is a mixture of an element and an organic compound. Carry out the following exercises on H. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test
(a) Put all of H in a beaker and add about 10cm\(^3\) of distilled water. Stir the mixture thoroughly and filter Keep both the filtrate and the residue. Test the filtrate with litmus paper.
(b) Divide the filtrate into two portions
(i) To the first portion add two to three drops of acidified potassium tetraoxomanganate (VII) and warm
(ii) To the second portion. add a few drops of a saturated solution of sodium hydrogentrioxocarbonate (IV)
(c)(i) Put all the residue in a test tube and add 5cm\(^3\) of dilute hydrochloric acid
(ii) To the resulting solution from (C)(i) above add aqueous sodium hydroxide in drops until it is in excess
(iii) From your inferences in (c)(i) and (c)(i) state what would be observed if 5cm\(^3\) of dilute trioxonitrate (V) acid were added to a portion of the residue and the mixture was warmed.
Explanation
| Test | Observation | Inference |
|
(a) H + water stirred and filtered filtrate + litmus |
Partially soluble forming a black solid and colourless filtrate Blue litmus turned red |
Soluble component is acidic |
|
(b)(i) Filtrate + acidified KMnO\(_4\) and warmed |
The KnO\(_4\) is decolourised |
Filtrate or water Soluble component is a reducing agent |
| (ii) Filtrate + saturated NaHCO\(_{3(aq)}\) | Effervescence occurs liberating a colourless gas which turns lime water milky | Gas is CO\(_2\) and the functional group present is alkanoic acid - COOH |
| (c)(i) - Residue + dil. Hcl | Effervescence occurs liberating a colourless odourless gas which gives a pop sound with burning splint | Gas is hydrogen from a metal |
| (ii) Solution from C(i) + NaOH aqueous | Dirty green ppt. insoluble in excess NaOH\(_{(aq)}\) |
The green colour probably due to Fe\(^{2+}\), Fe\(^{2+}\) present |
(ii) Brown fumes NO\(_2\) will be produced and the residue will dissolve to form a brown solution