WAEC Chemistry past questions and answers pdf for free reading 2024

Which of the following gases could be collected by downward displacement of air?
A. Chlorine
B. Hydrogen
C. Hydrogen chloride
D. Sulphur(IV) oxide

Which of the following substances has the lowest boiling point?
A. Aqueous sodium chloride
B. Ethanol
C. Tetrachloromethane
D. Water

The branch of science that deals with the nature and properties of substances and how one substance can be converted to another is known as
A. Biology
B. Chemistry
C. Geography
D. Physics

The electron configuration $1s^2 2s^2 2p_x^2$ contravenes the
A. Pauli’s exclusion principle
B. Aufbau’s principle
C. Octet rule
D. Hund’s rule

5. The oxidation number of chromium in \( Na_2Cr_2O_7 \) is

A. +2

B. +6

C. +7

D. +12

The most important ore of aluminium is
A. bauxite
B. haematite
C. magnetite
D. monazite

Bases normally
A. are corrosive
B. turn litmus paper from blue to red
C. turn litmus paper red to blue
D. are non-metal oxides

8. The product of the reaction between ethanol and excess acidified \( K_2Cr_2O_7 \) is

A. \( CH_2 = CH_2 \)

B. \( CH_3OH \)

C. \( CH_3COOH \)

D. \( CH_3CH_3 \)

9. The product formed when concentrated sodium chloride solution is electrolyzed using carbon electrodes is

A. chloride water

B. hydrochloric water

C. sodium hydroxide

D. sodium chlorate(I)

10. Which of the following statements about ammonium salt is correct?

A. Dissolves in water to form solution of pH > 7

B. Dissolves in water to form solution of pH < 7

C. Does not decompose on heating

D. Is insoluble in water

11. Ethanoic acid is an organic solid that can be purified by

A. decantation

B. distillation

C. crystallization

D. filtration

12. Which of the following functional groups is present in alkanolic acid?

A. -COOH

B. -OH

C. -COOR

D. -CHO

13. In ethanol, the attractive forces between adjacent molecules are

A. covalent bonds only

B. hydrogen bonds only

C. hydrogen bonds and van der Waal’s forces

D. van der Waal’s forces only

14. At 25°C, the saturated solution of a salt in water was found to contain 0.24g of the salt in 100cm³. What is the solubility of the salt in gdm⁻³?

A. 0.024

B. 0.024

C. 2.40

D. 24.0

15. The reaction represented by the equation:

\( Ni^{2+} (aq) + Fe(s) \rightarrow Ni(s) + Fe^{2+} (aq) \)

is a redox reaction because

A. \( Ni^{2+} \) ions are oxidized and Fe acts as an oxidizing agent

B. \( Ni^{2+} \) ions are oxidized and Fe acts as a reducing agent

C. \( Ni^{2+} \) ions are reduced and Fe acts as an oxidizing agent

D. \( Ni^{2+} \) ions are reduced and Fe acts as a reducing agent

16. Which of the following statements describes transition elements? They

A. are very reactive

B. have low melting point

C. possess variable oxidation state

D. form colorless water

17. Aluminum is suitable for making alloys for aircraft construction because it

A. is hard and brittle

B. is light and very resistant to corrosion

C. has high density and also a nonconductor of electricity

D. is amphoteric and allotropic

18. Which of the following arrangements of elements is in order of increasing ionization energy?

A. Al, S, P

B. S, P, Al

C. Al < Si, P, S

D. S, Si, P, Al

19. Consider the reaction represented by the equation:

\( C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 6H_2O(g) \)

If 0.1 mole of \( C_3H_8(g) \) was completely burnt, what volume of \( CO_2(g) \) would be produced at STP?

A. 22.4dm³

B. 6.72dm³

C. 2.24dm³

D. 0.103dm³

20. Naturally occurring boron is made up of 19.9% \( ^{10}B \) and 80.1% \( ^{11}B \). The relative atomic mass of boron is

A. 21.0

B. 10.8

C. 10.5

D. 10.0

21. The number of shared pair of electrons in a molecule of methane is

A. 2

B. 4

C. 6

D. 8

22. Isotopes of the same element have similar chemical properties because they

A. have the same number of protons

B. nuclei

C. neutrons

D. atoms

23. Which of the following household liquids would be effective in treating someone with too much acid in the stomach?

A. Strong salt solution with pH 7.0

B. Tomato juice with pH 4.1

C. Milk of magnesia with pH 10.5

D. Black coffee with pH 5.0

24. The percentage by mass of oxygen in \( MgSO_4 \cdot 7H_2O \) is

A. 26.0%

B. 45.5%

C. 71.5%

D. 84.0%

25. Catalysts alter reaction rates by

A. providing an alternative reaction pathway

B. lowering the energy of reaction

C. increasing the surface area of reactants

D. aligning the reactant molecules properly

26. Ethane of volume 400cm³ as completely burnt in excess oxygen according to the following equation:

\( 2C_2H_6(g) + 7O_2(g) \rightarrow 6H_2O(g) + 4CO_2(g) \)

Calculate the volume of steam that would be produced

A. 200cm³

B. 400cm³

C. 600cm³

D. 1200cm³

27. A saturated solution at 30°C will normally produce crystals at a temperature of

A. 50°C

B. 40°C

C. 35°C

D. 20°C

28. The following organic compounds are polymers except

A. rubber

B. starch

C. proteins

D. fats

29. According to the collision theory of reaction rates, which of the following conditions is not required for two molecules to react?

A. The molecules must come into contact

B. Molecules must collide in the correct orientation

C. Molecules must have enough energy to overcome activation energy

D. Molecules must have minimum loss of energy during collision

30. A weak acid is one which

A. is not corrosive

B. completely ionizes in water

C. does not produce salt with alkali

D. slightly ionizes in water

31. Which of the following conditions are necessary for the preparation of alkanotes from alkanols and alkanoic acids?

A. Water and NaOH

B. Cone. \( H_2SO_4 \) and heat

C. NaOH and heat

D. Water and aqueous HCl

32.  The volume of 22g of \( CO_2 \) at STP is equivalent to

(Given: C = 12, O = 16, molar volume at STP = 22.4 dm³)

A. 22.0 dm³

B. 22.44 dm³

C. 11.2 dm³

D. 5.6 dm³

33.  Pairs of outermost shell electrons which are not used in bonding are

A. lone pairs

B. bonding pairs

C. valence electrons

D. electrovalent electrons

34.** \( gX^2- \) and \( y^0 \) are

A. isomers

B. isotopes

C. allotropes

D. isoelectronic

35.   Pure water contaminated with quicklime will have a pH of

A. 1

B. 6

C. 7

D. 8

36.** The electron configuration of \( ^{29}Cu \) is

A. \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^{10} \)

B. \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^9 \)

C. \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} \)

D. \( 1s^2 2s^2 2p^6 3s^2 3d^{10} \)

37.** When **s** and **p** block elements react, the bond formed is

A. electrovalent

B. covalent

C. metallic

D. dative-covalent

38.** The hardest form of carbon is

A. charcoal

B. coke

C. diamond

D. graphite

39.** The metallic bonding in aluminium is strong because of the large number of

A. delocalized electrons

B. immobile electrons

C. lone pair electrons

D. valence electrons

40.** How many covalent bonds are formed by nitrogen?

A. 1

B. 2

C. 3

D. 4

41.** When an element exists in two or more forms in the same physical state, it exhibits

A. isotopy

B. allotropy

C. isobars

D. isomerism

42.** An atom of an element in the ground state contains **8 valence electrons**. The element is considered as

A. a metal

B. semi-metal

C. noble gas

D. halogen

43.  The main function of limestone in the **blast furnace** during the extraction of iron is to

A. act as a catalyst

B. remove impurities

C. act as a reducing agent

D. supply carbon (IV) oxide

44.** Which of the following is a monomer of polyethene?

A. Ethanol

B. Vinyl chloride

C. Ethene

D. Ethane

45.** Which of the following compounds is formed by the oxidation of ethanol?

A. \( CH_3CO_2H \)

B. \( C_2H_5CO_2H \)

C. \( CH_3OH \)

D. \( CH_3COCH_3 \)

46.** Tetraoxosulphate (VI) acid is considered as a heavy chemical because

A. its relative molecular mass is high.

B. a high tonnage is produced every year.

C. it is an inorganic chemical.

D. it is used to manufacture heavy chemicals.

47.** How many isomers can be formed from a compound with a molecular formula \( C_5H_{12} \)?

A. One

B. Two

C. Three

D. Four

48.** The oxidation number of iron in the free state is

A. 0

B. +1

C. +2

D. +3

49.** Water pipes are produced from

A. polyethene

B. perspex

C. polystyrene

D. polyvinyl chloride

50.** Consider the reaction represented by the following equation:

\[

xAl + yCl_2 \rightarrow zAlCl_3

\]

The values of \( x \), \( y \), and \( z \) respectively are

A. 2, 3, and 2

B. 2, 2, and 3

C. 1, 2, and 1

D. 1, 1, and 1