WAEC Chemistry 2020 Theory — Question 2

Model answer

(a)(i) Compounds A and B are geometric isomers. (ii) A is trans-1,2-dichloroethene; B is cis-1,2-dichloroethene. (iii) Yes, A and B will have the same chemical properties. (iv) This is because the compounds have the same functional group. (b)(i) Characteristic features of boiling: Boiling occurs throughout the body of a liquid; It occurs at a definite temperature, known as the boiling point of the liquid. (ii) I. The addition of crystals of sodium chloride (or any other impurity) will cause an increase in the boiling point of water. II. Reduction of the atmospheric pressure causes a decrease in the boiling point of water. (c)(i) Boiling occurs at a fixed temperature (known as the boiling point of the liquid), while evaporation occurs at all temperatures. A saturated solution contains the maximum amount of solute it can hold at that temperature (in the presence of undissolved solute), while an unsaturated solution contains less than the amount of solute it can hold at that temperature. (ii) Ways to make a saturated solution dissolve more solute: Increasing the temperature; Increasing the volume of the solvent. (iii) Factors that could affect the solubility of a solid in a liquid: Nature of the solute; Nature of the solvent; Temperature.