Free 2018 Waec Gce Chemistry Questions And Answers Expo/Runz

Free 2018 Waec Gce Chemistry Questions

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Gas > liquid > Solid


Solid > liquid > gas






(I) Magnesium from 0 to +2

(II) Hydrogen changes from 1 to 0


I —> Magnesium is oxidized

II —> Hyfrogen is reduced




(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


It decreases the boiling point as the boiling point of water is proportional to the magnitude of atmosphere pressure.


It dictates the rate of reaction and also optimize the amount of product formed.


C3H7CooH —> Butanoic acid

(CH3)3COH —> Butan-1-ol


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


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.

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(iii) The solubility of gases is a direct consequences of pressure changes due to the partial pressure of the gas molecules.


3F2 + 3H2O -> 6HF + O3


Basicity of an acid is the number of replaceable hydrogen ions in the acid.





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


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



i)it i solid at room temperature

ii)it does not contain molecule

iii)they do not dissolve in non-polar solvent



i)Eq1- actuation energy for in catalyzed reaction

ii)Eq2 – actuation energy for catalyzed reaction.



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.


It is endothermic because it involves bond breaking and heat is absorbed in the process.


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.

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(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


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


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.


(i) When Gribb’s free energy is negative.

(ii) When Entropy ie ?s must be positive as the total entropy must increase.


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.


2Na(s) + 2H2O(l) —> 2NaOH(aq) + H2(g)

Ca(s) + 2H2O(l) —> Ca(OH)2 + H2(g)


Mass of lead (ii) trioxocarbonate iv


= 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

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X = 267×35/207 = 45.1g

=45.1g of PbCO3


(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.


i) Iron impurity

ii) mud or Sand.



(i)Carbon (II) oxide

(ii) Carbon (iv) oxide


It is because there is increasing surface area of the broken coal than in the lumps of coal










Sodium oxide


Aluminium oxide


NO2 gas




Redox reaction


Iron(ii) ion is oxidized to iron(iii) ion

ie Fe2+ –> Fe3+


A = Delivery tube

B = Calcium oxide


Ca(OH)2+2NH4Cl –> CaCl2+2NH4.H2O


Ammonia gas


The gas is less dense than air


(I) B is used to drive the gas

(II) Upward delivery



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