Question 3
3 (a)(i) Give one use for each of the following laboratory apparatus:
I desicator;
II volumetric flask;
III. glass rod. [3 marks]
(ii) List two examples each of the following oxides:
I. neutral oxides;
II. amphoteric oxides. [4 marks]
(b) Outline a technique that could be used in purifying a sample of sugar contaminated with sand.
(c) State what would be observed when each of the following reactions is carried out.
Addition of:
(i) HNO3(aq) to CuCO3 solid;
(ii) acidified KMnO4 to C2H4;
(iii) iodine solution to a paste of unripe plantain. {5 marks]
Observation
The expected answers include:
(a) (i)
I.- used to keep chemicals/substances/solids dry
- to dry chemicals/substances/solids
II.- for preparation of standard solutions
- to measure a fixed volume of liquids
III. used to
- stir or mix chemicals/ liquids for laboratory purposes.
- dislodge precipitate from containers.
- guard transferring of liquid from a beaker.
(ii) I. - Nitrogen (I) oxide - N2O
- Nitrogen (II) oxide - NO
- Carbon (II) oxide - CO
- Water/Hydrogen oxide - H2O
II. - Zinc oxide - ZnO
- Lead (II) oxide - PbO
- Aluminium oxide - Al2O3
- Berryllium oxide - BeO
(b)- To the mixture, add distilled water, stir to dissolve the sugar
- filter the mixture to remove sand
- Evaporate the filtrate on water bath/ in the Sun
- allow to cool to obtain sugar crystals
(c)(i) Effervescence of (colourless) gas/ gas evolved, blue solution forms
(ii) Purple colour turns colourless/ discharged
(iii) Blue-black colouration observed