WAEC Chemistry Revision Questions Part 2

 

40 More WAEC Chemistry Revision Questions (True/False) - Part 2

Continue your WAEC preparation with part 2 of our core chemistry concepts quiz. Read the statement, choose True or False, and review the breakdown.

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1. Isomers are compounds with the same molecular formula but different structural formulas.

True

Because their atoms are arranged differently, isomers often exhibit different physical and chemical properties.

2. Temporary hardness in water is caused by calcium sulfate ($CaSO_4$).

False

Temporary hardness is caused by calcium or magnesium hydrogen trioxocarbonate(IV), $Ca(HCO_3)_2$. Calcium sulfate causes permanent hardness.

3. Ammonia gas turns damp red litmus paper blue.

True

Ammonia is the only common alkaline gas encountered in the WAEC syllabus.

4. Boiling a liquid happens when its vapor pressure equals the atmospheric pressure.

True

This is the definition of the boiling point. If atmospheric pressure drops, the boiling point drops as well.

5. A reducing agent is itself reduced during a redox reaction.

False

A reducing agent reduces another substance but is itself oxidized in the process.

6. In an electrolytic cell, anions migrate toward the cathode.

False

Anions (negative ions) migrate to the anode (positive electrode), while cations (positive ions) move to the cathode.

7. Standard Temperature and Pressure (S.T.P.) corresponds to 0°C and 1 atm.

True

At these conditions ($273\text{ K}$ and $760\text{ mmHg}$), one mole of any gas occupies a molar volume of $22.4\text{ dm}^3$.

8. Electrovalent compounds form individual molecules in the solid state.

False

Ionic compounds form a continuous, repeating three-dimensional giant crystal lattice structure of ions, not distinct molecules.

9. The catalyst used in the Haber Process for making ammonia is finely divided iron.

True

Finely divided iron speeds up the reaction between nitrogen and hydrogen, while alumina or potassium oxide acts as a promoter.

10. Carbon(II) oxide ($CO$) is an acidic oxide.

False

Carbon(II) oxide is a neutral oxide. It does not react with acids or bases to form salt and water.

11. Hydrocarbons are organic compounds containing carbon, hydrogen, and oxygen.

False

Hydrocarbons contain carbon and hydrogen only.

12. Fractional distillation separates mixtures based on differences in boiling points.

True

Liquids with lower boiling points distill over first, allowing miscible liquids like crude oil fractions to separate cleanly.

13. Phenolphthalein indicator is pink in an acidic solution.

False

Phenolphthalein is colorless in acidic solutions and turns pink/crimson in alkaline solutions.

14. Heavy water contains an isotope of hydrogen known as deuterium ($^2H$).

True

Heavy water ($D_2O$) uses deuterium, which has one proton and one neutron, making it heavier than normal hydrogen.

15. Increasing the temperature of a gaseous reaction always shifts the equilibrium to the right.

False

According to Le Chatelier's principle, an increase in temperature shifts the equilibrium in the direction of the endothermic reaction.

16. Graphite conducts electricity due to the presence of mobile/delocalized valence electrons.

True

Each carbon atom in graphite bonds covalently to three others, leaving one free valence electron per atom to conduct current.

17. The major component of natural gas is methane.

True

Natural gas is primarily composed of methane ($CH_4$), usually making up over 80% of its volume.

18. Efflorescent substances absorb water from the air to form wet crystals.

False

Efflorescent substances lose their water of crystallization to the atmosphere when exposed. Deliquescent substances absorb moisture.

19. Helium is preferred over hydrogen in filling observation balloons because it is safer.

True

Even though hydrogen is lighter, it is highly flammable and explosive. Helium is an inert noble gas and will not catch fire.

20. The valency of an element is determined by the number of protons in its nucleus.

False

Valency is determined by the number of valence electrons an atom gains, loses, or shares to achieve a stable octet.

21. Calcium trioxocarbonate(IV) ($CaCO_3$) decomposes when heated to produce carbon(IV) oxide gas.

True

Thermal decomposition of limestone yields calcium oxide (quicklime) and $CO_2$ gas.

22. The process of fermentation produces ethanol and oxygen gas.

False

Fermentation of sugars by yeast enzymes produces ethanol and carbon(IV) oxide ($CO_2$) gas, not oxygen.

23. Elements in the same period on the periodic table have the same number of electron shells.

True

For example, all elements in Period 3 have exactly three occupied electron shells.

24. Concentrated tetraoxosulfate(VI) acid is used to dry hydrogen sulfide gas ($H_2S$).

False

Concentrated $H_2SO_4$ reacts chemically with $H_2S$ via a redox reaction, so it cannot be used to dry it. Fused calcium chloride is preferred.

25. Zinc protects iron from rusting through a process called sacrificial protection (galvanization).

True

Zinc is more reactive than iron, so it corrodes preferentially, sparing the underlying iron from oxidation.

26. A basic salt is formed by the complete neutralization of an acid by a base.

False

Complete neutralization forms a normal salt. A basic salt is formed by the incomplete neutralization of a polybasic base.

27. Alpha particles have a higher penetrating power than gamma rays.

False

Alpha particles have the lowest penetrating power (stopped by paper). Gamma rays have the highest penetrating power.

28. The functional group of organic acids (alkanoic acids) is the carboxyl group (-COOH).

True

Compounds like ethanoic acid ($CH_3COOH$) contain this specific structural configuration.

29. Mass number is the sum of protons and neutrons in an atom's nucleus.

True

Also known as the nucleon number, it defines the approximate atomic mass of an isotope.

30. Concrete is a chemical compound.

False

Concrete is a heterogeneous mixture of cement, sand, gravel, and water. Its constituents retain their individual properties.

31. The empirical formula represents the simplest whole-number ratio of atoms in a compound.

True

For example, the empirical formula of hydrogen peroxide ($H_2O_2$) is simply $HO$.

32. Esterification is the reaction between an alkanol and an alkanoic acid.

True

This reversible acid-catalyzed reaction yields a sweet-smelling ester and water.

33. Standard solutions are solutions of known concentration.

True

They are prepared carefully in volumetric flasks to serve as reference standards during titrations.

34. Chlorine gas is collected by the downward displacement of air.

False

Chlorine is denser than air, so it is collected by upward displacement of air (downward delivery).

35. Hydrochloric acid ($HCl$) will liberate hydrogen gas when reacted with copper metal.

False

Copper is below hydrogen in the reactivity series and cannot displace hydrogen from dilute acids.

36. The extraction of aluminum from bauxite is done via electrolytic reduction.

True

Because aluminum is highly reactive, carbon reduction will not work. It must be dissolved in molten cryolite and electrolyzed (Hall-Héroult process).

37. An exothermic reaction absorbs heat from the surroundings.

False

Exothermic reactions give off heat energy to the surroundings, resulting in a temperature rise. Endothermic reactions absorb heat.

38. Fine sand can be separated from ammonium chloride by sublimation.

True

Ammonium chloride transforms directly from a solid to a gas when heated, leaving the sand behind.

39. The local production of dye from plants involves the extraction method known as solvent extraction.

True

A solvent (like water or ethanol) is used to selectively dissolve and rinse out the colored pigments from plant tissues.

40. Soap forms scum with soft water.

False

Soap lathers easily with soft water. It only forms scum when it interacts with the calcium and magnesium ions found in hard water.