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DIR Return to: WAEC/NECO 2016/2017 UPDATE
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#Post#: 27--------------------------------------------------
2016/2017 WAEC VERIFIED CHEMISTRY ANSWERS
DIR By: anephy
Date: April 18, 2016, 8:21 am
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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
==================================
5ai)
Na2S2O3 ===>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)
I2KNo3. -------->2KNO3 + O2
2AgNo3 --------->. 2Ag + 2No
5ci)
Calcium chloride in a solution can give rise to
crystal using filteration and evaporation to dryness.
The sol is filtered into filtrate and residue b4
evaporation to dryness takes place.
5cii)
- Because of presence of hydrogen bonding in NH3
- Because Iodine as higher molecular mass than
chlorine
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
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