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VERIFIED 2016 WAEC CHEMISTRY ESSAY ANSWERS

Verified Theory
1a )
nucleons is the collective name for two
important
sub-atomic particles : neutrons and
protons 1b)
Graham 's law of diffusion states that at
a
constant temperature and presure , the
rate of
diffusion of a gas is inversely proportional to the
square root of it density 1c )
because when aluminum is exposed to
moist
air, a thin continuous coating of
aluminum oxide
is formed , which prevents futher attack of the
aluminium by atmospheric oxygen and
water or
steam under normal conditions 1d)
i ) electron - affinity
ii ) electron - negativity
iii ) ionization - energy 1e )
i ) the molecule of real gases occupies
space and
there are forces of the attraction
between them
ii ) real gases do liquefy when their temperature
droops . 1f )
i ) used in seperation of different
component of
crude oil .
ii )it is used for separating acetonic
from water iii ) it is used for obtaining different
gases from air
for industrial use . 1g)
i ) concentration of ions in electrolyte
ii )the nature of the electrode
iii )the position of ions in the
electrochemical
series 1h)
i ) substitution reaction
ii )addition reaction 1i )
i ) carbon dioxide
ii )water vapour
iii ) carbon monoxide 1j )
i ) centrifugation
ii )sieving
iii )evaporation to dryness
================================== 2a )
i ) isotopy
ii ) they have the same number of
proton (atomic
number) but different mass number
iii ) oxygen ,carbon iv )1s ^2, 2s ^2, 2p^6 ,3 s ^2, 3p^5 2bi)
PHYSICAL PROPERTIES
METAL
i ) high melting and boiling point
ii ) they are good conductor of heat and
electricity NON -MATEL
i ) they have lower melting and boiling
point
ii )they are poor conductors of heat and
electricity . CHEMICAL PROPERTIES
METAL
i ) they form basic and ampheric oxides
ii )the react by electron lose or donation
of
electron NON -METAL
i ) the form acidic oxides
ii )the react by sharing and accepting
electrons 2bii )
i ) Al 2 O 3(Aluminum oxide )
ii ) sodium hydride (NaH )
iii )zinc trioxocarbonate( iv )ZnCo 3
iv )silicon tetrachloride (SiCl 4) 2ci )
i ) variable oxidation states
ii ) complex ion formation
iii ) they possess strong metallic
bonding 2cii )
1s ^2, 2s ^2, 2p^6 , 3s ^2, 3p^6, 3 d^10,
4 s ^2 2ciii )
Zinc is not considered as a typical
transition
element bacause it has only one
oxidation state
of +2 , it metallic ion are not coloured and it is not
used as a catalyst. 2d)
Na 2Co 3 + MgCl 2 -- -- > 2NaCl + MgCo 3
1mole 1mole 2 mole 1mole
molar mass of Na 2 Co 3 = 2 * 23 + 12 *
1 + 16 *
3 = 46+ 12+48 = 106g ================================== 3ai)
structral isomerism is the existance of
two or more compounds ( known as
isomers) with the same molecular
formula but different molecular
structures 3ai)
i) tertiary alkanol
ii) secondary alkanol
iii) primary alkanol
3bi)
i) 2[CH3 CH2 COOH ] 2K(s)----> ii) [CH3 CH2 COO ] K + H2 i) 2[CH3 CH2 COOH ] +2 K(s) ------> 2[ CH3
CH2 COO ] K + H2
ii) CH3 CH2 COOH + C4 H9OH
HEAT---->CH3 CH2 COO C4 H9 + H20
H2SO4
iii)CH3 CH2 CH2 CH20H + H^+ KMnO4------> CH3 CH2 CH2 CH2 - 0H
EXCESS
3bii)
i) potassium ethanoate,hydrogen
ii) butyl propanoate and water
iii) enthanal 3c)
the percentage composition of the
hydrocarbon
= 100
H + C = 100
14.3 + C =100 C= 100 - 14.3
C= 85.7% ============================== 5ai )
Na 2S 2O 3 ===> 2 + 2x + 6 = 0
2x = 6 - 2 = 4
X = 4/2
X = 2
The oxidation number of sulphur is 2 5aii )
Rhombic & monoclinic 5aiii )
- Both are tetravalent
- both are allotrope of carbon 5bi)
CO2 & Chloroflorocarbon 5bii )
There is increase in sun radiation
reaching the
earths surface ie Global warming
5biii )
ThunderStorm 5iv )
I 2KNo 3. - -- - -- -- > 2KNO3 + O 2
2AgNo 3 -- -- - -- -- > . 2Ag + 2No 5ci )
Calcium chloride in a solution can give
rise to
crystal using filteration & evaporation
to dryness .
The sol is filtered into filtrate & residue b4
evaporation to dryness takes place . 5cii )
- Because of presence of hydrogen
bonding in
NH 3
- Because Iodine as higher molecular
mass than chlorine 5di)
Mol of Nacl = Mass / MM
= 5 . 85/ 58. 01
= 0 . 1mol
From the equation
2mol of Nacl gives 2mol of HCL, 0. 1mol of Nacl
gives 0. 1mol of Hcl
Vol of Hcl = 0. 1 x 22. 4 = 2. 24mol /
dm^3

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