Waec Chemistry Past Questions and Answers

Question 1716:

• WAEC 2021

Consider the following energy profile diagram and use it to answer the question that follows



The enthalpy change of the reaction is ____________

A. E\(_{A}\)
B. E\(_{B}\)
C. E\(_{C}\)
D. E\(_{D}\)

Question 1717:

• WAEC 2021

Consider the following energy profile diagram and use it to answer the question that follows



The energy profile diagram illustrates ____________

A. An endothermic reaction
B. An exothermic reaction
C. A spontaneous reaction
D. A redox reaction

Question 1718:

• WAEC 2021

(a) Distinguish between molecular formula and structural formula
(b) List three factors that determine the ionization energy of an atom.
(c) State the two conditions necessary for the establishment of a chemical equilibrium
(d) Consider the following table

Element	A	B	C
Ionization energy KJ mol\(^{-1}\)	619	518	594

(d)(i) State which of the elements is the strongest reducing agent.
(ii) Give a reason for the answer stated in (d)(i)
(e) State Graham's law of diffusion
(f) Consider the following salts: Mg(NO\(_{3}\))\(_{2}\), CaCO\(_{3}\), Na\(_{2}\)SO\(_{4}\). State which of the salts is/are:
(i) readily soluble in water:
(ii) insoluble in water.
(g) Classily each of the following products as addition polymer or condensation polymer:
(i) protein:
(ii) perspex:
(iii) nylon.
(h) Define atomic radius.
(i) Explain briefly why ethanol has a higher boiling point than propane even though they both have comparable molar masses.
(j) State three significance of the pH value in everyday life.

Question 1719:

• WAEC 2021

(a)i. State two characteristics of a homologous series.
(ii) Explain briefly why there are differences in the reaction of ethane and ethene.
(b) When crystals of sodium chloride were warmed with concentrated tetraoxosulphate( VI) acid, a gas was evolved.
(i) Name the gas.
(ii) State two physical properties of the gas.
(iii) Write a balanced chemical equation for the reaction.
(c)i. What are hydrocarbons?
(ii) State two natural sources of hydrocarbons.
(iii) A hydrocarbon contains 83% of carbon by mass. Calculate its empirical formula. [H=1.0, C=12.0]
(d) Draw and label a diagram of a set-up that could be used to electroplate a copper ornament with silver