WAEC Chemistry Revision Questions (True/False) - Part 3

 

40 Additional WAEC Chemistry Revision Questions (True/False) - Part 3

Keep testing your chemistry readiness with part 3 of our revision series. Analyze the statement, identify if it's True or False, and check the reason why.

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1. Isotopes of the same element have the same number of neutrons.

False

Isotopes have the same number of protons (atomic number) but different numbers of neutrons (mass number).

2. Kinetic Molecular Theory states that gas particles have perfectly elastic collisions.

True

An elastic collision means that no net kinetic energy is lost when the gas particles collide with each other or the container walls.

3. Silicon(IV) oxide ($SiO_2$) has a simple molecular structure with low melting points.

False

Quartz ($SiO_2$) has a giant covalent lattice structure (macromolecule), giving it an exceptionally high melting point.

4. The dehydration of ethanol at 170°C using concentrated $H_2SO_4$ yields ethene.

True

At 170°C, elimination occurs to produce ethene gas. (Note: at a lower temperature of 140°C, ethoxyethane/ether is formed instead).

5. Zinc blende is a major ore used for the extraction of copper.

False

Zinc blende ($ZnS$) is the primary ore used to extract zinc. Copper is extracted from copper pyrites ($CuFeS_2$).

6. An acid is a substance that produces hydrogen ions ($H^+$) or hydroxonium ions ($H_3O^+$) as the only positive ions in aqueous solution.

True

This is the classic Arrhenius definition of an acid, which applies directly to standard WAEC objectives.

7. Water has a maximum density at 4°C.

True

This anomalous expansion of water causes ice to form at the surface of lakes while the denser 4°C water remains at the bottom, sustaining aquatic life.

8. Adding a non-volatile solute to a solvent raises its freezing point.

False

It causes freezing point depression (lowers the freezing point) and boiling point elevation.

9. Nitrogen is chemically inert at room temperature because of the strong triple covalent bond between its atoms.

True

The triple bond requires huge amounts of activation energy to break, making $N_2$ gas highly unreactive under normal conditions.

10. Permanent hardness of water can be removed by adding washing soda (sodium trioxocarbonate(IV)).

True

Washing soda reacts with the soluble calcium and magnesium sulfates/chlorides to precipitate them out as insoluble carbonates.

11. Aluminum is a transition metal.

False

Aluminum is a main-group metal in Group 3 (Group 13). Transition metals are located in the d-block (Groups 3 to 12).

12. Oxidation always happens at the anode of an electrochemical cell.

True

Whether it is a galvanic (voltaic) cell or an electrolytic cell, oxidation always takes place at the anode. Anagram to remember: AN OX (Anode = Oxidation).

13. Starch turns iodine solution deep blue-black.

True

This is a standard qualitative analysis test used to confirm the presence of starch or iodine.

14. The dynamic equilibrium position changes when a catalyst is added to a reversible reaction.

False

A catalyst increases the rate of both forward and backward reactions equally. It helps reach equilibrium faster but does not alter its position.

15. Sulfur(IV) oxide ($SO_2$) acts as a bleaching agent by a process of oxidation.

False

$SO_2$ bleaches via reduction. This bleaching is temporary because atmospheric oxygen can re-oxidize the substance back to its original color. (Chlorine bleaches via oxidation).

16. Petroleum is a mixture of hydrocarbons.

True

Crude oil is a complex subterranean mixture containing various alkanes, cycloalkanes, and aromatic compounds.

17. Noble gases have high electron affinity values.

False

Noble gases have stable outer octet electronic configurations, meaning they have almost zero tendency to gain or accept extra electrons.

18. Polyethene is produced via an addition polymerization reaction.

True

Polyethene is formed when thousands of unsaturated ethene monomers link together without the loss of any small co-product molecules.

19. Methyl orange indicator turns yellow in alkaline solutions.

True

Methyl orange is red/pink in acidic environments, orange at the end-point, and turns distinctly yellow in basic solutions.

20. Graham's Law states that the rate of diffusion of a gas is directly proportional to the square root of its density.

False

It is inversely proportional to the square root of its density or relative molecular mass. Lighter gases diffuse faster.

21. Concentrated hydrochloric acid ($HCl$) is used to test for ammonia gas by forming dense white fumes.

True

The reaction between ammonia gas and hydrogen chloride vapor yields dense white fumes of solid ammonium chloride ($NH_4Cl$).

22. The valence shell of a chlorine atom contains 7 electrons.

True

Chlorine has an atomic number of 17, with an electronic configuration of 2, 8, 7. It requires 1 more electron to complete its octet.

23. Soapless detergents are biodegraded easily by microorganisms in water bodies.

False

Many synthetic (soapless) detergents contain highly branched hydrocarbon chains that bacteria cannot break down easily, leading to water pollution and foam build-up.

24. Thermosetting plastics can be melted and reshaped repeatedly when heated.

False

Thermosetting plastics decompose and harden permanently upon heating due to extensive cross-linking. Thermoplastics are the ones that can be repeatedly remelted.

25. Carbon(IV) oxide ($CO_2$) turns lime water milky due to the formation of calcium trioxocarbonate(IV).

True

The milkiness is caused by the precipitation of insoluble $CaCO_3$. If the gas continues to bubble through, the milkiness clears up as soluble $Ca(HCO_3)_2$ forms.

26. Air is a chemical compound containing nitrogen and oxygen.

False

Air is a mixture. Its components can be separated by physical methods like fractional distillation of liquid air, and they retain their original properties.

27. Electronegativity increases across a period from left to right on the periodic table.

True

As the nuclear charge increases and atomic radius decreases across a period, the nucleus exerts a stronger pull on bonding electron pairs.