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WAEC 2017: 100% Verified Chemistry Practical Queation & Answers
WAEC April 10, 2017 • 4 years ago • No Comment Yet

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2017 WEAC (CHEMISTRY PRACTICAL) 100% VERIFIED QUESTIONS

# ?WAEC 2017 CHEMISTRY PRACTICAL ANSWERS?

1)
Tabulate
Rough- 24.10,0.00,24.10
First- 23.80, 0.00, 23.80
Second- 23.75, 0.00, 23.70
Third- 23.75, 0.00, 23.75
Average volume of A used = 23.80 + 23.70 + 23.75cm^3/3
=23.75cm^3
1bi)
CAVA/CcVc=2/1
Cc=CAVA/2VC
=0.100*23.75Moldm^-3/2*25.00
=0.0475moldm^-3
amount of A used = 0.100x VA/1000=0.100*23.75/1000 =0.00237
2moles Of A = 1mole of C
0.002375mol of A = 0.002375mol/2
100cm^3 of C contain 0.00237*100mol/2*25 =0
1000cm3ofCcontained0.002375x1000mol
2×25
=0.0475mol
concentration of C in moldm-3 =0.0475moldm-3
1bii)
Molar mass of Bing mol-1:
Molar mass of Na2CO3.yH2O=mass concentration of Bingdm-3
molar concentration of Binmoldm-3
=13.6gdm-3
0.0475moldm-3
=286gmol-1
1biii)
Molar mass of Na2CO3 =[(2×23)+12+(16×3)]=106gmol-1
Mass of anhydrous Na2CO3=106×0.0475gdm-3
=5.035gdm-3
Mass of water=13.6-5.035gdm-3
=8.565gdm-3
Mass of Na2CO3 =Molar mass of Na2CO3
Mass of water y×Molar mass of water
5.035=106
8.565 18y
y =106×8.565
5.035×18
=10
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2a)
Tabulate
Test
(i)Fn + H2O, then filter
Observation
White residue and blue filtrate was observed
Inference
Fn is a mixture of soluble and insoluble salts
Test
(ii)Filtrate + NaOH(aq) in drops, then in excess
Observation
A blue gelatinous precipitate which is insoluble in excess NaOH(aq) was formed
Inference
Cu2 + present
Test
(iii)Filtrate + NH3(aq) in drops, then in excess
Observation
A pale blue gelatinous precipitate was formed. The precipitate dissolves or is soluble in excess NH3(aq) to give a deep blue solution
Inference
Cu2+ confirmed
Test
(iv)Filtrate + dil.HNO3 +AgNO3(aq)
Observation
No visible reaction White precipitate formed
Inference
Cl- present
Test
+NH3(aq) in excess
Observation
Precipitate dissolved in excess NH3(aq)
Inference
Cl- confirmed
2bi)First portion of residue +NaOH(aq) in drops, then in excess
Observation
White powdery precipitate which is insoluble in excess NaOH(aq)
Inference
Ca2+ present
Test
2bii)Second portion of residue + dil.HCl
Observation
Effervescence/bubbles; colourless, odourless gas evolved.
Gas turns lime water milky and turns damp blue litmus paper red.
Inference
Gas is CO2
CO3^2- or HCO3- present
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3i) Lime juice is cacitic in nature and the color of methyl orange in active medium is Red
3ii) Iron
(iii)chloride will be reduced to iron
(ii) with the yellow deposit of Sulphur
3iv)Addition of ethanoic acid to k2lo3 results to the liberation of a colourless or odourless gas co2 Which turns lime water milky

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