CHEMISTRY WAEC RUNS 2018 - Round the clock entertainment and update.

CHEMISTRY WAEC RUNS 2018



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2 a )
– Observation –
part of the C dissolves ,colourless filtrate salt
– Inference –
C is a mixture of soluble salt
2 bi)
– observation –
white precipitate formed
– Inference –
Cl is present
2 bii )
– Observation –
precipitate dissolves
– Inference –
Cl confirmed
2 biii)
– Observation –
colourless gas evolved with characteristic choking smell , turns litmus paper blue
– Inference –
Gas is NH 3
2 c )
– Observation –
Residue dissolves liberating a colourless gas which turns lime water milky
– Inference –
gas is CO 2
CO ^ 2 – 3 present
3i)A white precipitate of barium sulphate will be formed by the instant reaction between barium chloride and sulphuric acid.
BaCl2 + H2SO4 = BaSO4 + 2HCl
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
3b)Iron sulfide reacts with hydrochloric acid, releasing the malodorous (rotten egg smell) and very toxic gas,hydrogen sulphide. FeS + 2 HCl → FeCl2+ H2S
3i)A white precipitate of barium sulphate will be formed by the instant reaction between barium chloride and sulphuric acid.
BaCl2 + H2SO4 = BaSO4 + 2HCl
3b)Iron sulfide reacts with hydrochloric acid, releasing the malodorous (rotten egg smell) and very toxic gas,hydrogen sulphide. FeS + 2 HCl → FeCl2+ H2S
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