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NABTEB GCE Chemistry OBJ and Theory Expo Answer — 2017 Nov/Dec

 

100% Verified NABTEB GCE Chemistry Questions and Expo Answer – Nov/Dec 2017

NABTEB GCE 2017 Nov/Dec Chemistry OBJ and Essay Answer and Solution to the questions.

Chemistry OBJ:
1-10=bdcacccbdc
11-20=bcccbadaac
21-30=ccdbadacbc
31-40=cddcaaccbd
41-50=dbcadbacba

GOODLUCK
1ai)
In a degenerated orbital there are no two electrons that can have the same four Quantum numbers.
1aii) 
i)An ionic bond involves the loose and gain of electrons. 
ii)A covalent bond involves the sharing of electrons by two atoms where both atoms contribute.
iii)A dative bond involves sharing of electrons but only one atom contribute the electrons to be shared 

1bi)
Periodic law states that atoms are arranged in order Of increase in their atomic number
1bii) 
i)Does not form common compounds – k10
ii)liberates hydrogen from cold water – J3
iii)Are halogens – N17
iv)Are in the same group – J31L13
v)Forms ions by loss of three electrons – L13 

1c) 
– Water
– Ammonia – Triangular pyramid 
– Methane – Tetrahedral 
– sulphur (iv) oxide – linear

2ai)
LAW OF CONSTANT COMPOSITION: states that all pure sample of a particular chemical compound contain the same elements combined in the same proportion by mass.
2aii)
-sample C: 5.00/4.06×100/1
= 500/4.06
= 123.15

-sample D: 6.60/5.35×100/1
= 660/5.35
= 123.36

approximately
sample c: 123g
sample d: 123g
hence, the percentatge by mass is the same, this proved the law of definite(constant) proportion.

2bi)
AMPHOTERIC OXIDE: are oxides of metals which can behave both as basic oxides and as acidic oxides i.e they can react with both acids and alkalics to form salts and water only.
2bii)
i)ZNo: formed from 2ZN(s)+O2 –> 2Zno
hence; Zno(s)+H2So4(aq) –> ZnSO4(aq)+H2O(i)
ii)Al2O3: formed from 4Al(s)+3O2(g) –> 2Al2O3(s)
iii)Pbo: formed from 2pb(s)+O2(g) –> Pbo(s)
Therefore: amphoteric acide from Zno above shows that, amphoteric oxides behave as basis forming a salt and water only.
2biii)
i)Acidic oxides e.g CO2, SO4, NO2, e.t.c
ii)basic oxides e.g Na2O, CaO

2c)
i)IDEAL GAS:
A hypothetical gas that obeys exactly all postulates of the kinetic-molecular theory.
2cii)
i)change in temperature
ii)variation in earth gravitation

2c)
iii)gas forms a liquid – condensation 
iv)liquid forms a gas – evaporation
v)gas forms a solid – sublimation

3ai) 
Allotropes are atoms of the same element in the same physical state but in different forms. 
3aii) 
–TABULAR FORM–

Diamond:
*Transparent.
*Very strong solid
*Octahedral shape

Graphite:
*Blank
*Soft solid 
*Hexagonal shape
3aii) 
Diamond -> For cutting glass 
For drilling limestones 

Graphite -> For making pencils
For lubricating metals

3bi) 
An electrolytic cell is made up of an electrolyte, electrodes and sources of electricity where the electrolyte decomposes.

3bii) 
2 Faraday deposits 63.5g of copper
i.e 2x96500c deposits 63.5g of copper
298,500c deposits Xg of copper
X = 298,500×63.5 / 2×96500
=98.211g

3ci) 
A reducing agent is the substance that is oxides in a redox reaction
3cii)
They will turn purple permanent to pink. 
3ciii) 
i)Pipeline product manufacturing company in portharcourt 
ii)Dangote cement in lokoja

4ai) 
A saturated solution contains the maximum amount of solute that the solvent can take at a particular temperature.
4aii)
A dilute solution contains more solution that solute contain at a temperature.
4aiii) 
A super saturated solution contains more than enough solute than the solvent can contain at the temperature. 

4b) 
Iodine – 
Chlorine – For killing micro organisms 
Alum – For coagulation 

4ci) 
i)It reacts with water to form acid
ii)It changes blue litmus paper to red
iii)It reacts with ammonia gas to form salt. 
4cii)
i)As an oxidising agent because it reduced to nitrogen gas. 
ii)As an acidic oxide because the product formed are salt and water only.

4di) 
Disco sulphate(iii) acid – Hso2
4dii)
C2HSOH ——->CH3COOH+H20
4diii) 
C2HSOH ——-> C2H4+H20

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