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Thursday, July 6, 2017

NECO CHEMISTRY ANSWERS | NECO EXPO CHEMISTRY

NECO Chemistry Questions 2017 | The National Examinations Council is an examination body in Nigeria that conducts the Senior Secondary Certificate Examination and the General Certificate in Education in June/July and December/January respectively.


NECO 2017 Chemistry Questions Online

NECO 2017 Chemistry QuestionsKeep visiting this page as update will be made in jiffy

CHEMISTRY OBJ :
1-10 DCBBCBBEDC
11-20 CADECEBBDC
21-30 EEBABDADBE
31-40 AECCACDDDC
41-50 DABABCBBCA
51-60 CBBAABCADE
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 = 148g/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 (CaCl2)
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)
NH4Cl+Ca(OH)2—–>CaCl2+2NH3+2H2O
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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5ai)
i)carbon monoxide and hydrogen
ii)carbon monoxide,carbon dioxide,hydrogen and nitrogen
5aii)
i)colloids is an intermediate between true solution and a suspension
ii)condensation is the process by which water vapour in the air is changed to liquid water
5bi)
CaC03+2HCl—–>CaCl2+H2O+CO2
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)Cr2O7^-2
=2Cr + C-2*7) = -2
2Cr – 14 = -2
2Cr = -2 + 14
2Cr/2 = 12/2
Cr = 6
ii)Cr2{SO4}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
==================================
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(N2O)
ii)nitrogen(v)oxide(N2O5)
iii)nitrogen(iv)oxide(NO2)
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)
P1 V1 = P2 V2
given that
P1 = 900mmHg
P2 = 750mmHg
V1 = 300cm^3
V2 = ?
V2 = P1V1/P2
V2 = 900*300/750
V2 = 270000/750
V2 = 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
==================================
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 40/23
1.74/1.74 = 1
the emperical formula is NaO2
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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Completed. enjoy.

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