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WAEC GCE 2016 Chemistry (Alternative To Practical) Question and Answers now available here
WAEC September 15, 2016 • 4 years ago • No Comment Yet

NO1,2,3 COMPLETED

1a)
i) TABULATE
burette reading/cm^3 | 1    |2   |  3
final reading  |  39.5   |   29.80  |   19.40
initial reading   |  19.55   |  10.50  |  0.0
volume of E used  |  19.70  |  19.30   |  19.40

ii) Na2CO3(aq)^2HNO3(aq) — 2NaNO3(aq) + CO2(g) + H2O(c)
average volume of E used = 19.70+19.30+19.40/3
=19.47cm^3

1bi)
From the information given,
nD=1, nE=2,
CD=?, CE=0.0905mol/dm^3
VD=20.0cm^3, VE=19.35cm^3
Using: CDVD/CEVE=nD/nE
CD=CEVEnD/VDnE
=(0.0905*19.35*1)/(20.0*2)
=1.751175/40
=0.04377
CD=0.0438mol/dm^3

1bii)
Since 0.04377mol is in 1000cm^3
xmol will be 350cm^3
x=0.04377*35.0/1000
=1.5322/1000
=0.00153mol/dm^3 at 25C
Hence the solubility is 0.00153mol/dm^3

1biii)
From the stoichiometry
1 mole of Na2CO3 produces 1 mole of CO2
0.00153mol of Na2CO3 produces 0.00153mole of CO2
mass=molar mass*number of mole
molar mass Na2CO3=23*2+12+16*3
=46+12+48
=106g/mol
mass of CO2=12+16*2
=12+32
=44g/mol
106g Na2CO3 produces 44g of CO2
0.0153*106 will produce y
y=0.153*106*44/106
=0.153*44
y=6.732g of CO2
Hence mass of CO2 produced is 6.732g

=========

(2a)
Inference: SO3^2- suspected

(2b)
(i) Inference: insoluble salt
(ii) Inference: SO3^2- confirmed
(iii) Inference: Cu2+ suspected
Cu2+ confirmed
(iv) Obseravation:
-Blue gelatineous precipitate
-Precipitate dissolves

(2c)
(i) CuSO3
(ii) Copper (ii) trioxosulphate (iv)
==========

3ai)
SO2(g)

3aii)
A->To dry the gas
B->To detect the type of gas that was dried

3aiii)
A->P4O10
B->KMno4/Blue litmus paper

3bi)
-It is an acid that turns moist blue litmus paper red
-It is colourless and poisonous gas with an irritating smell

3bII)
The irritating smell

3bii)
Downward delivery
Chlorine gas (Cl2(g))

3ci)
I-T,U,V
II-X,Y,Z

3cii)
W

3ciii)
I-U
II-V
========
COMPLETED