[Waec Answer] Waec 2018 Chemistry 3 Practical (Alternative A) Questions And Answers Now Available.
Chemistry 3 (Practical) (Alternative A) Questions And Answers.
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NOTE: Please Use Your School End Point.
1a)
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 =8 cm^ 3
= 24. 10cm^ 3
1bi)
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
1bii)
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
1biii)
mole = con mol x vol ( dm ^ 3 )
= 0 . 15* 20/ 1000
= 0 . 003 moles
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(2a)
TEST: C about 5cm3 of distilled water
OBSERVATION: C dissolves to form a clear solution;
Turns blue litmus paper to pink
INFERENCE: C is a soluble salt;
C is fairly acidic
(2ai)
TEST: 1st portion of C NaOH(aq) in drops;
then excess
OBSERVATION: pale-blue precipitate forms in drops of NaOH(aq) which persists in excess of NaoH(aq)
INFERENCE: cu² present.
(2aii)
TEST: 2nd portion of C NH3(aq) in drops and then in excess
OBSERVATION: pale blue precipitate forms in drops of NH3(aq).
Ppt dissolves to form a deep blue coloration.
INFERENCE: Cu² present.
Cu² confirmed
(2aiii)
TEST: 3rd portion of c AgNO3(aq) HCL(aq)
OBSERVATION: a creamy white ppt forms.
INFERENCE: Halogen/Halides present.
(2bi)
TEST: D about 5cm³ of distilled H2O
OBSERVATION: D dissolves to form a clear solution.
The test tube feels warmth
INFERENCE: D is a soluble salt.
(2bii)
TEST: 2cm³ of D HCL(aq)
OBSERVATION: effervescence occurs, an odourless and colourless gas evolved. Precipitate dissolves in dil HCL(aq)
INFERENCE: CO32-, so32-present
CO32- 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)When solid iron filings are added to dilute aqueous Hydrochloric acid, Iron (II)chloride or ferrous chloride is formed , with the liberation of Hydrogen gas.
Fe (s) 2HCl (aq) ……..> FeCl2(aq) H2 (g)
Published at 74months ago
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UNDER MAINTENANCE
Correct.. Tanks so much, u are the best!
nice one you are the best campus
Tank u sir