Chemistry Paper 3 WASSCE (PC), 2018

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