Waec Chemistry

CHEM-OBJ
1CAACABCDBC
11BABAADBDCA
21BCCAABCDCB
31ABCBCCCBBC
41ABDBBBAABB
======================
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^6,3s^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) Al2 O3(Aluminum oxide)
ii) sodium hydride (NaH)
iii)zinc trioxocarbonate(iv)ZnCo3
iv)silicon tetrachloride (SiCl4)
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, 3d^10, 4s^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)
Na2Co3 + MgCl2 —-> 2NaCl + MgCo3
1mole 1mole 2mole 1mole
molar mass of Na2 Co3 = 2 * 23 + 12 * 1 + 16 *
3 = 46+12+48 = 106g
106g of Na2Co3 produced 84g of MgCo3
; 106g = 84g
xg= 3.36g
84 * x = 106 * 3.36
x = 106 * 3.36/84
x=356.16/84
x=4.24g
4.24g of Na2Co3 is needed to produce
3.36g of MgCo3
=============================
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%
============================================
(4ai)
calcium chloride, CaCl2
(4aii)
to the unknown ssubstance in a gas jar, add small quantity of
lime water. if the gas is carbon(iv)oxide, it turns lime water
milky while carbon (ii) oxide has no effect
(4bi)
oxygen is releasedf abundantly from air and nitrogen is
produced by the reaction of potassium trioxonitrate(v) with
concentrated hydrochloric acid
(4bii)
oxygen gas rekindle a lighted splint while nitrogen does not
(4ci)
Bauxite is preferred because it is readily available in the
earth crust
(4cii)
-trioxosilicate(iii)
-carbon(iv)oxide
(4ciii)
-it helps to purify the bauxite
(4civ)
it is difficult to extract aluminium by chemical reduction of
aluminium oxide in amphoteric
(4cv)
AL2O3+NaOH=>Na2O + Al+ H20
Sent from my BlackBerry® wireless handheld from Glo Mobile.