WAEC CHEMISTRY ANSWERS 2021

Here is the waec chemistry answers 2021

Chemistry answers…

((1a)

A molecular formula consists of the chemical symbols for the constituent followed by numeric subscripts showing the number of atoms of each element present while structural formula consists of symbols for the atoms connected by short lines that represent chemical bonds.

(1b)

(i) Screening effect

(ii) Size of atom

(iii) Nuclear change

(1c)

(i) The reaction must proceed both forward and backward i.e reversible

(ii) DG = O

(1d)

(i) B

(ii) It has the least ionization energy among the three

(1e)

Graham’s law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of their densities provided other conditions remained constant

(1f)

(i) Na2SO4. Mg(NO3)2

(ii) CaCO3

(1g)

(i) Protein – Addition polymer

(ii) Perspex – Condensation polymer

(iii) Nylon – Condensation polymer

(1h)

Atomic radius can be defined as the half distance between the nucleus of two covalently bonded atoms.

(1i)

Ethanol has a higher boiling point than propane because it has stronger force of attraction than propane which has a weak van der waal’s force.

(1j)

(i) It aids the digestion of food

(ii) It aids the action of enzymes

(iii) It controls the availablity of nutrientsMore coming.

2ai)

(i) They have the same method of preparation

(ii) They have the same chemical properties

(2aii)

(i) Ethane has a single bond while Ethene has a double bond

(ii) They belong to different homogeneous series

(iii) They have different molecular formula and structural formula

(2bi)

(i)HCl

(ii) – It is colourless

– It has an irritating odour

(iii) 2Nacl(aq) + H2SO4(aq) —> Na2SO4(aq) + 2Hcl(g)

(2ai)

(i) They have the same method of preparation

(ii) They have the same chemical properties

(2aii)

(i) Ethane has a single bond while Ethene has a double bond

(ii) They belong to different homogeneous series

(iii) They have different molecular formula and structural formula

(2bi)

(i)HCl

(ii) – It is colourless

– It has an irritating odour

(iii) 2Nacl(aq) + H2SO4(aq) —> Na2SO4(aq) + 2Hcl(g)

(2ci)

Hydrocarbons are compounds having hydrogen and carbon atoms only. Examples are alkanes, alkenes, alkynes etc

(2cii)

(i) Coal

(ii) Crude oil

(2ciii)

C H

83% 100.83

83/12 17/1

6.92/6.92 17/6.92

1 2

Empirical formula = CH2

(2d)

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