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CHEMISTRY PRACTICAL NECO GCE 2015 FREE EXPO ANSWERS




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Tuesday 3rd Nov. 2015
CHEMISTRY PRATICAL
2.00PM-4PM
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Please Arrange This In A Tabular Form

(1ai)
Titration:
Rough:
1:
2:
3:

Final Reading(cm^3)
Rough = 22.60
1 = 45.00
2 = 28.20
3 = 45.00

Initial Reading(cm^3)
Rough = 0.00
1 = 22.60
2 = 5.80
3 = 22.40

Volume Of A Used(cm^3)
Rough = 22.60
1 = 22.50
2 = 22.40
3 = 22.60

(1aii)
Average Volume Of A Used = 22.50 + 22.40 + 22.60/3
= 67.5/2
= 22.50cm^3


(1 bi )
Given That
Molar Mass of B = NaoH
= (1 x 23 + 1 x 16 + 1 x 1 ) = 23 + 16 + 1
= 40 g

Volume = 500 cm ^ 3 = 500 / 1000 = 0 .5 dm^ 3
Mass = 2 . 15 g

Mass Conc = mass / volume = 2 .15 / 0 .5 = 4 . 3
Mass Conc = 4 .3

(1 bii )
Given That
VB = 25 cm ^ 3
VA = 22 . 50 cm ^ 3
CA = ?
CB = 0 .1075
NA = 1
NB = ?
:-
CAVA/ CBVB = NA / NB
CA x 22 .50 / 0 .1075 x 25 = 1 / 2

CA x 22 .50 x 2 = 0 .1075 x 25
45 CA / 45 = 2 .6875 / 45

CA = 0 . 0597 moldm^ - 3



2 ai)
X is a mixture of solute and insoluble salts

(2 aii )A white precipitate is formed- > Cl ^ - present

(2 aiii )The white precipitate is insoluble in NH 3 (aq )- > Cl ^ - present

(2 aiv ) A gas is evolved with pungent odour.it turns red litmus paper to blue - > Gas is Co 2 from Co 3 ^ 2 -

(2 bii ) white precipitate - > Pb ^ 2 +, Zn ^ 2 + and Al^ 3 + are present
In excess - > PPt dissolves- > Zn^ 2 +

(2 biii) White PPt - > Al ^ 3 + and Pb ^ 2 +
In excess - > Insoluble in excess - > Pb ^ 2 +

(2 c )
Phosphorus - > acidic
Magnessium- > Neutral




(3a)
(i)
-hydrogen sulpide gas
-sulphur iv oxide
-chloride
(ii)
they should be prepared in fume cupboard

(3b)
(i)glucose and fructose
(ii)evaporation
(iii)
-temperature
-concentration
-physical state




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Posted By KellyChi On 11:15 Tue, 03 Nov 2015

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