CHEMISTRY WAEC ANSWERS

 [9/2, 2:54 PM] Mr_Sàmuél: (2ai)

They are isomers

(2aii)

A - Trans 1,2 dichloroethane

B - Cis 1,2 dichloroethane

(2aiii)

Yes

(2aiv)

They contain the same functional group the single bond. The only difference is the polarity(physical property)

The Cis - polar compound while Trans-1, -di chloroethane is non polar

(2bi)

(i) Temperature remains constant during boiling

(ii) There is change of state during boiling

(2bii)

I - It will increase the boiling point of water.

II - It will reduce the boiling point of water.

(2biii)

Boiling occurs at a specific temperature While Evaporation occurs at almost all temperatures.

(2ci)

An unsaturated solution is one that contains less than the maximum amount of solute that can dissolve at a given temperature While A saturated solution is one that contains maximum of solute that can be dissolved in it at that temperature.

(2cii)

(i) By increasing the temperature of the solution.

(ii) By increasing the amount of the solute.

(2ciii)

Temperature.

(2di)

Mole is a standard scientific unit for measuring large quantities of very small entities such as atoms, molecules, or other specified particles

(2dii)

MgO(s)+2HCl(aq) ---> MgCl(aq)+H2O(l)

From the equation of reaction; 1 mole of MgO = 2 moles of HCl

Hence n = cv/100

where c = 0.1moldm-³; v = 25.0cm³

No of mole of HCl = n = 0.1x25/1000

= 2.5 x 10-³ moles

Hence the no of moles ofMgO required = 2.5/2 x10-³

But n = m/M = reacting mass/ Molar mass ---> m = nM = 1.25x10-³ x 40

= 50 x 10-³ = 0.05g of MgO.

(2e)

(i) They are malleable

(ii) They are ductile

(iii) They are good conductors of heat and electricity

[9/2, 2:58 PM] Mr_Sàmuél: (5a)

(i)Ammonia (NH³)

(ii)Hydrogen chloride gas(HCl)

(5aii)

To show that hydrogen chloride is extremely soluble in water.

(5aiii)

Fill a round-bottomed fask with dry hydrogen chloride through a tube A and air through another tube B. Add a few drops of water through B and close the tubes. Invert the flask into a trough of water containing blue litmus solution. The water turns red.

(5bi)

(i)Petrochemical industries

(ii)Pharmaceutical industries.

(5bii)

(i)Pollution of water bodies by chemical waste

(ii)Pollution of the air

(iii)Radioactive particles are released

(5ci)

(i)Coke

(ii)Coal gas

(iii)Coal tar

(5cii)

(i)Coal gas=> important gaseous fuel

(ii)Coke => used as a reducing agent

(5di)

(i)calcium tetraoxosulphate(iv)

(ii)calcium hydrotrioxocarbonate(iv)

(5dii)

(i)By boiling.

(ii)Addition of caustic soda.

(5diii)

(i)Hard water contains dissolved minerals and therefore tastes better.

(ii)The calcium salts in hard water help animals to build strong teeth and bones.