WAEC GCE 2018/19 JAN/FEB CHEMISTRY PRACTICAL QUESTIONS& ANSWERS

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Thursday 1st February, 2018
Chemistry 3 [Alternative to Practical Work] 3:30pm – 5:00pm
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(1ai)
Burrette readings/cm3:|titre 1|titre2|titre3
Final readings |33.20 |49.60 |1.50
Initial readings |16.40 |16.40 |16.65

(1aii)
Average volume of acid used
= 16.40+16.40+16.65(cm3)/3
=49.45cm3/3
=16.48cm3

(1b)
(I) Concentration of Y(OH)2.XH2O in mol/dm3
Using CAVA/CBVB = a/b
CA= 0.025mol/0.25dm3 = 0.1mol
VA = 16.48cm3
CB = ?
VB = 25.00cm3
a = 1mol
b = 2 moles
.:. CAVA/CBVB =a/b
CB = CAVA*B/VB*a
= 0.1 mol/dm3 * 16.48cm3 * 2 moles / 25.00 * 1 mol
CB = 3.296/25
CB = 0.131mol/dm3

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(2bi)
The reagent is the aliphatic monocarboxylic acids that contains one carboxyl group per molecule
[CnH2n+1COOH]

(2bii)
It is observed that they are called fatty acids due to some of them are found in natural fats and oil by changing the -e- ending the corresponding alkane to -oic acid

Pls Draw a table: for Ethanedioic acid(Oxalic acid), Cis-butenedioic(Maleic acid) & 2,3 dihydroxybutanedioic acid(tartaric acid)

Under Ethanedioic acid(Oxalic acid):
COOH
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CooH

Under Cis-butenedioic(Maleic acid):
H-C-COOH
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H-C-COOH

Under 2,3 dihydroxybutanedioic acid(tartaric acid):
H
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HO-C-COOH
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HO-C-COOH
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H
;

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