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WAEC GCE 2018 Chemistry Answer Obj and Essay– Nov/Dec Expo

 

WAEC GCE 2018 Chemistry ANSWER

Verified WAEC GCE 2018 Chemistry ANSWER

OBJ
CHEMISTRY OBJ:
1-10: CCDBACBABA
11-20: BDDDCDBAAA
21-30: CAADCCCAAB
31-40: CBBCABCDBC
41-50: BACCAABACC
—————————————————————-

CHEMISTRY THEORY
(1a)
Gas > liquid > Solid

(1aii)
Solid > liquid > gas

(1bi)
PH>7

(1bii)
PH>7

(1ci)
(I) Magnesium from 0 to +2
(II) Hydrogen changes from 1 to 0

(1cii)
I —> Magnesium is oxidized
II —> Hyfrogen is reduced

(1ciii)
HCL

(1di)
(i) Boiling occurs throughout the entire volume while evaporation occurs at the surface
(ii)It involves the formation of bubbles while evaporation does not form bubbles

(1dii)
It decreases the boiling point as the boiling point of water is proportional to the magnitude of atmosphere pressure.

(1e)
It dictates the rate of reaction and also optimize the amount of product formed.

(1f)
C3H7CooH —> Butanoic acid
(CH3)3COH —> Butan-1-ol

(1g)
Functional groups are responsible for their different chemical behavior or properties so that organic compounds with smaller functional group would behave similarly.

(1h)
Solids in liquid:
(i) It depends on the nature of temperature changes or exothermic or endothermic as affect by the temperature of the liquid.
(ii) The surface area of solid is lesser, they dissolves less as compound to gases in the same volume.
(iii) Pressure does not affect the solubility of the solids

Gas in liquid:
(i) It depends on the average kinetic energy as affect by temperature of the liquid.
(ii) The surface area of gases are higher so they dissolve more in a given volume of water.
(iii) The solubility of gases is a direct consequences of pressure changes due to the partial pressure of the gas molecules.

(1i)
3F2 + 3H2O -> 6HF + O3

(1j)
Basicity of an acid is the number of replaceable hydrogen ions in the acid.

—————————————————————-

CLICK HERE FOR NUMBER 1

*******************

2ai)
carbon – 0.48/12 , 0.04/0.04 , 1
hydrogen – 0.08/1 , 0.08/0.04 , 2
chlorine – 1.42/35.5 0.04/0.04 , 1
Therefore CH2CL
The electrical formular = CH2CL
2aii)
The molar mass of the compound is 99
Hence (CH2CL)n = 99
(12 + 2C1) + 35.5)n = 99
12 + 2 + 35.5
(495)n = 99
Therefore n = 2
Hence the molar formula = (CH2CL)2
C2H4CL2
2bi)
i)it i solid at room temperature
ii)it does not contain molecule
iii)they do not dissolve in non-polar solvent
2ci) CLICK HERE FOR THE IMAGE
2cii)
i)Eq1- actuation energy for in catalyzed reaction
ii)Eq2 – actuation energy for catalyzed reaction.
—————————————————————-
(3ai)
When potassium chloride dissolves in water, the bond in the solid particle breaks thereby increasing the kinetic energy of the particle to move. Particles in solid state have restricted or static movement unlike those in the form of ions or gases.

(3aii)
It is endothermic because it involves bond breaking and heat is absorbed in the process.

(3bi)
An underground iron pipe is less likely to erode if it is bonded at intervals with magnesium rod because the magnesium is more electro positive thereby absorbing the water or little oxynegn it is exposed to. In addition, corrosion is influenced by the presence of oxygen and water, therefore underground iron pipe will be exposed to little oxygen and water.

(3bii)
(i) First, conversion of Iron II to Iron III
Fe²+(aq) + e- —>Fe³+(aq)

(ii) Exposure to oxygen and water vapour.
4Fe(s) + 3O2(g) + xH2O(l) –> 2Fe2O3 xH2O
Iron rod Iron rust

(3biii)
The iron in water will be oxidized since there is dissolved oxygen and atmospheric oxygen & a brown deposit of Iron occurred.

(3ci)
A spontaneous reaction is a reaction that can exist freely on its own without any external factor. A reaction is said to be spontaneous if ?G, is the Gribb’s free energy is negative. ?G = -ve
An example is rusting of Iron.

(3cii)
(i) When Gribb’s free energy is negative.
(ii) When Entropy ie ?s must be positive as the total entropy must increase.

(3Ciii)
This is because sodium is more electropositive than calcium. Also the heat evolved in the reaction with sodium is far greater than the heat of solution released with calcium and water at the same temperature.

(3civ)
2Na(s) + 2H2O(l) —> 2NaOH(aq) + H2(g)
Ca(s) + 2H2O(l) —> Ca(OH)2 + H2(g)

(3d)
Mass of lead (ii) trioxocarbonate iv
PbCO3
= 207 + 12 + 3(16)
207 + 12 + 48 = 267g
1mole of PbCO3 contain 1 mole of Pb
267g of PbCO3 = 207g of Pb
Xg of PbCO3 = 35.0g of P
X = 267×35/207 = 45.1g
=45.1g of PbCO3

(3e)
(i) Covalent bond
(ii) Ionic bond
—————————————————————-

4ai) addition of chlorine to the
Water To Kill germs and organic substances

ii) Addition of slake line me to
remove hardness in water

iii) addition of alum to coagulate and participate the impurities

iv) passage of water through the activated carbon i.e animal charcoal go remove color and odour from water
V) passage of water through the filter sand bed to remove the precipated impurities

Vi) finally, storage of Water
the tank for onward Supply to the tenk.
(4bi)
i) Iron impurity
ii) mud or Sand.

—————————————————————-
(5ai)
(i)Carbon (II) oxide
(ii) Carbon (iv) oxide

(5aii)
It is because there is increasing surface area of the broken coal than in the lumps of coal

(5aiii)
CH4

(5aiv)
Coke

(5bi)
SO2

(5bii)
MnO2

(5biii)
Sodium oxide

(5biv)
Aluminium oxide

(5bv)
NO2 gas

(5ci)
Cl2+FeCl—–>FeCl3

(5cii)
Redox reaction

(5ciii)
Iron(ii) ion is oxidized to iron(iii) ion
ie Fe2+ –> Fe3+

(5di)
A = Delivery tube
B = Calcium oxide

(5dii)
Ca(OH)2+2NH4Cl –> CaCl2+2NH4.H2O

(5diii)
Ammonia gas

(5div)
The gas is less dense than air

(5dv)
(I) B is used to drive the gas
(II) Upward delivery

(5e)
Petrol


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