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Tuesday 21st June 2023/2022
Paper III&II: Objective & Essay – Chemistry b

1ai)
A mixture contains two or more constituents which can
easily be seperated by physical methods
1aii )
magnesium trioxonitrate ( v ) = Mg ( NO3) 2
molar mass of Mg ( NO3) 2
=( 1* 24) + 2 ( 14* 1 + 16* 3)
=24 + 2 ( 14 + 48 )
=24 + 28 + 96 = 148 g/mol
% of nitrogen = 2* 24* 100 /148
% of nitrogen = 48 *100 /148
% of nitrogen = 4800 /148
% of nitrogen = 32 .43%
1aiii )
i ) calcium oxide ( CaO )
ii ) calcium choride ( CaCl 2)
1bi)
CnH2n +1OH
1bii )
hydrolysation
1biii )
i ) displacement reaction
ii ) double decomposition reaction
iii ) decomposition reaction
iv ) catalytic reaction
v ) reversible reaction
1biv )
i ) endothermic heat change
ii ) exothermic heat change
1ci )
i ) methyl orange
ii ) phenolphthalein
iii ) litmus
1cii )
NH 4Cl +Ca( OH) 2 — — – > CaCl 2+2 NH3 +2H2 O
1ciii )
it is collected by upward delivery
1civ )
mass of gas = 1. 58* 22. 4 = 35. 392
vapour density = 35.392 /1
relative molecular mass= V . D * 2
=35. 392* 2
relative molecular mass= 70. 784
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NEC- NAIJA EXAM CENTER

5ai)
i ) carbon monoxide and hydrogen
ii ) carbon monoxide, carbon dioxide , hydrogen and
nitrogen
5aii )
i ) colloids is an intermediate between true solution andt
a suspension
ii ) condensation is the process by which water vapour
in the air is changed to liquid water
5bi)
CaC 03 +2HCl- — — > CaCl 2 +H2O +CO 2
5bii )
i ) it is used in fire extinguishers
ii ) it is used in the manufacturing of mineral water
iii ) carbon ( iv ) oxide is used as a coolant in nuclear
reactors
5biii )
i ) Cr 2O 7^-2
=2Cr + C – 2* 7) = – 2
2Cr – 14 = -2
2Cr = -2 + 14
2Cr /2 = 12/2
Cr = 6
ii ) Cr 2{ SO 4} 3
2Cr + 3 ( – 2* 1 + – 2*4 ) = 0
2Cr + 3 ( – 2 – 8) = 0
2Cr + 3 ( – 10) = 0
2Cr – 30 = 0
2Cr /2 = 30/2
Cr = 15
5ci )
vulcanization is a chemical process of converting
netural rubber or related polymers into more durable
materials through the addition of sulphur or other
equivalent curatives or accelerators
5cii )
Time Taken( t ) for 6. 35g of copper ( ii ) tetraoxosulphate
solution
Cu^2^+ + 2c – — — – -> Cu
Q = 2* 63. 5* 95600
Q = 12255500
Q = 1t
12255500/10 = 10 *t /10
t = 1225550 /60 = 204258 .3
5ciii )
Latex
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4ai)
electrolytic cell is a cell that consist of a container of
electrolyte with two electrodes connected to a suitable
direct current supply
4aii )
i ) daniel cell
ii ) Leclanché cell
4aiii )
i ) copper
ii ) tin
4aiv )
action of dilute acide on zinc
4av )
Zn +2HCl- — – — > ZnCl +H2
4bi)
i ) dinitrogen ( i ) oxide ( N 2O )
ii ) nitrogen ( v ) oxide ( N2O 5)
iii ) nitrogen( iv ) oxide ( NO 2)
4bii )
charle’ s law states that the volume of a fixed mass of
gas varies directly with the absolute
( kelvin) temperature provided the pressure remains
constant.
4biii )
P 1 V 1 = P 2 V2
given that
P 1 = 900mmHg
P 2 = 750mmHg
V 1 = 300cm ^3
V 2 = ?
V 2 = P 1V 1/P 2
V 2 = 900* 300 /750
V 2 = 270000 /750
V 2 = 360cm ^3
4biv )
% composition carbon
= 12 /( 12* 6) + ( 1* 6) * 100 %
= 12 /72+6 * 100
= 12 /78 * 100% = 1200/78 %
%composition of carbon = 15 .38 %
4c )
TABULATE
-THERMOPLASTS –
i ) it melts when heat is applied to it
ii ) highly recycled
-THERMOSETS –
i ) does not melt when heat is applied
ii ) cannot be recycled
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2ai)
ionization energy deals with electron loss while
electron loss while electron afinity deals with electron
gain
2aii )
i ) they are used to dry gases
ii ) they are used to recover valuable vapours from
industrial effluents and refine petroleum
2bi)
TABULATE
-RHOMBIC SULPHUR-
i ) bright yellow in colour
ii ) it is octohedral in shape
-MONOCLINIC SULPHUR-
i ) amber in colour
ii ) it is needle like in shape
2bii )
oxygen = 60%
sodium = 40 %
oxygen 60 /16
3.75 /1.74 = 2
sodium 40/23t
1.74 /1.74 = 1
the emperical formula is NaO 2
2biii )
sodium( iv ) oxide
2ci )
i ) x is hydrophobic region
ii ) y is hydrophilic religion
2cii )
i ) for laundry purpose
ii ) for fuel
2ciii )
i ) the distance of outermost electron from the nucleus
ii ) the size of the positive nuclear charge
iii ) the screening effect of inner electrons
2civ )
period law states that the properties of the elements
are a period function of their atomic number
2di)
n- — pentane — – — > n- — butane – – — -> 2– –
methylbutane- – -2, 2- – -dimethylpropane
2dii )
i ) glucose
ii ) galactose
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