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CHEMISTRY (OBJ & ESSAY) NECO GCE 2015 FREE EXPO ANSWERS






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Thursday 12th Nov. 2015
CHEMISTRY(OBJ & ESSAY)
2.00PM-5.00PM
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ANSWERS LOADING......

CHEMISTRY OBJ:
1-10: CBDDADABDD
11-20: CADABDCCEB
21-30: DABACBBBDA
31-40: BACBBDACBA
41-50: DDDAAEACAE
51-60: BAEDEDACAB


(1ai)
A saturated solution is a solution which contain solute which is enough to satisfy the solvent which can no longer contain anymore solute

(1aii)
-Fertilizer application
-Oil spillage
-Sewage
-Refuse

(1aiii)
-Hard water wastes soap
-It gives taste to pure water
-It destroys pipelines

(1bi)
-Availability of raw material ie limestone
-Availability of reliable electricity
-Availability of transportation
-Availability of favourable government policy

(1bii)
Positive effect:
-It develops the economic state of the economy
-It creates more job opportunities

Negative effect:
-It causes noise pollution
-It causes environmental or land pollution

(1ci)
An electrochemical cell is one which generates electricity through chemical reaction

(1cii)
-Electrolytic cell generates electricity through electrolysis while Electrochemical cell generates electricity through chemical reaction
-Electrolytic cell long-lived electric life can be recharged while Electrochemical cells cannot be recharged



(3ai)
2Na+2H2O->2NaOH+H2

(3aii)
Isotopes are elements with the same atomic number but different mass number

(3bi)
Contact process
V2O5 catalytic

(3bii)
SO2+H2O->H2SO3
H2SO3+H2SO4->H2SO7(oleum)
H2S2O7+H2O->2H2SO4

(3ci)
Temporary and permanent hardness
-Temporary hardness-Ca(HCO3)2
-Permanent hardness-CaSO4

(3ciii)
I-Solution is the combination of a solute(solid form)and solvent(liquid form)
II-Suspension is the combination of solute in excess compared to the solvent

(3di)
-Transition metals possess coloured ions
-They have catalytic properties
-They possess complex ions

(3dii)
Complex ion is an ion which especially metallic ion at its centre with a number of other molecules or ions surrounding it



(4ai)
-Conductor is usually in solid state while Electrolyte are usually in liquid or molten state
-Conductors cannot be charge while the electrolyte can be recharged

(4aii)
-Electrolysis is used for electroplating process
-It used for extraction of metals from their ores
-It can be used for purifying metals

(4bi)
The rate of chemical reaction is the speed at which reactants combine together to give products

(4bii)
Daniel cell and Bird's cell


(4biii)
DRAW THE DIAGRAM

(4ci)
Faraday's first law of electrolysis states that d amount of metal deposited during electrolysis is directly proportional to the quality of electricity passed through the electrolyte

m proportional Q
m proportional It
m=ZIt/96500*e
=3*2*60*60*27/96500*3
m=2.0g



(5ai)
Thermal acid catalytic cracking

(5aii)
Addition polymerization occurs when two monomers react with each other and other small molecules are generated while condensation polymerisation occurs when generation of small molecules products like water

(5aiii)
Transluscence test on white paper

(5bi)
i. 2-methylbutane
ii. 2-2-dimethylpropane

(5bii)
CH4+Cl2->CH3CL+HCl

(5biii)
Radioactivity is the process by which electromagnetic particles are emitted from nuclei as a result of nuclear instability

(5ci)
I (238,92)U->(234,90)Th+alpha
II (14,6)C->(14,7)N+e^-

(5cii)
Physical properties:
-It is the lightest gas
-It gives a pop sound when ignited

Chemical properties:
-It burns to give steam
-It reacts with light high electropositive ion to form acids

(5ciii)
Tritium,deuterium and protium












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