WAEC 2018 EXPO: Chemistry 3 (Practical) Alternative A


Paper: Chemistry 3 (Practical)

Please Use Your School End Point

.

1a)
Volume of pepette = 25.00Cm^2
Indicator Used = Methyl Orange
Tabulate
BURETTE READING|ROUGH|1ST|2ND|3RD|
Final reading Cm^3|25.00|34.00|29.20|24.10|
Initial Reading Cm^3|0.00|10.00|5.00|0.00|
Volume Of Acid Used In Cm^3|25.00|24.00|24.20|24.10|
Average Volume of Acid used =(24.00+24.20+24.10/3)cm^3
=24.10cm^3


2a)
-Observation-
part of the C dissolves,colourless filtrate salt

-Inference-
C is a mixture of soluble salt

2bi)
-observation-
white precipitate formed

-Inference-
Cl is present

2bii)
-Observation-
precipitate dissolves

-Inference-
Cl confirmed

2biii)
-Observation-
colourless gas evolved with characteristic choking smell, turns litimus paper blue

-Inference-
Gas is NH3

2c)
-Observation-
Residue dissolves liberating a colourless gas which turns lime water milky

-Inference-
gas is CO2
CO^2-3 present

3a)
I)Desiccator- use for preserving moisture sensitive items

ii)Volumetric flasks are used for precise dilutions and
preparation of standard solutions.

iii)Glass rod are used to mix chemicals and liquids for
laboratory purposes .

3ii)
i)Amphoteric is Al2O3

ii) Neutral oxide is H2O

3iii) Crystallization

3b.
1. hno3aq to cuco3 solid. a light blue solid,
precipitates is formed

2. acidified kmno4 to c2h4. c2h4 is oxidized to
ethane-1,2-
diol

3. iodine solution to a paste of unripe plantain. a
bluish-black color is produced with iodine


 


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