WAEC 2018 Chemistry Practical Expo Answer | WAEC Chemistry Practical Expo Answer Solutions 2018/2019

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Chem- Pract – Answers
Pls Use Your School End Point .
1 a )
Volume of pepette = 25. 00Cm ^ 2
Indicator Used = Methyl Orange
Tabulate
BURETTE READING | ROUGH | 1 ST| 2 ND | 3 RD |
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
1 bi)
Con in mol/ dm 3 = conc in g / dm ^ 3 / molar mass
con of B in g / dm ^ 3 = 4 . 80/ 0 . 25 = 19. 2 g / dm ^ 3
molar mass = Fe + 2 Cl = 56+ 2 ( 35. 5 )=127 g / mol
conc in mol/ dm ^ 3 = 19. 2 / 127 = 0 . 15mol/ dm ^ 3
1 bii )
using CAVA / CBVB = NA / NB
CA* 11. 80/ 0 . 15* 20= 1 / 5
CA= 0 . 15* 20* 1 / 11. 80* 5
CA= 0 . 05moldm ^ – 3
1 biii)
mole = con ( mol/ dm ^ 3 ) x vol ( dm ^ 3 )
= 0 . 15* 20/ 1000
= 0 . 003 moles
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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
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
3c)
The iron dissolves, releasing hydrogen and making an iron chloride solution:
Fe + 2HCl → FeCl₂ + H₂