JAMB Past Questions and Answers - Page 9

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41.

When a substance is oxidized, it

A.

Loses electrons

B.

Gains oxygen atoms

C.

Gains electrons

D.

Loses protons (H+ ions)

Correct answer is A

When a substance is oxidized, it loses electrons. Oxidation is a chemical reaction that involves the moving of electrons. Specifically, it's a process that involves the substance losing electrons. This is an old definition of oxidation, based on the oxygen's role in reactions. The modern definition of oxidation involves an increase in oxidation state by a molecule, atom, or ion.

42.

What is the symbol used to represent an alpha particle?

A.

α

B.

γ

C.

δ

D.

β

Correct answer is A

An alpha particle is represented by the Greek letter 'α'. Alpha particles are a type of ionizing radiation ejected by certain types of radioactive materials. They consist of two protons and two neutrons, so they can be represented as a Helium-4 nucleus.

43.

Which of the following is a common property of non-metals?

A.

Exist as solids at room temperature

B.

Tend to gain electrons in chemical reactions

C.

High thermal conductivity

D.

Readily form cations in chemical reactions

Correct answer is B

Tend to gain electrons in chemical reactions. Non-metals typically have a high electronegativity and tend to gain electrons to achieve a stable electron configuration. This results in the formation of negatively charged ions (anions) during chemical reactions.

44.

What is the mass percentage of carbon (C) in methane (CH4)? (The molar mass of carbon is approximately 12 g/mol.)

A.

25%

B.

12%

C.

75%

D.

50%

Correct answer is C

The molar mass of methane (CH4) is calculated by adding the atomic masses of carbon (approximately 12 g/mol) and hydrogen (approximately 1 g/mol). Therefore, the molar mass of CH4 is 12 g/mol + 4 x 1 g/mol = 16 g/mol. The mass percentage of carbon in CH4 is given by (mass of carbon / total mass) x 100% = (12 g / 16 g) x 100% = 75%.

45.

What type of reaction is involved in the formation of alkanols from alkenes?

A.

Elimination reaction

B.

Redox reaction

C.

Substitution reaction

D.

Addition reaction

Correct answer is D

Alkanols can be formed from alkenes through an addition reaction. In this reaction, the carbon-carbon double bond of the alkene is broken, and a hydroxyl group (-OH) is added to one of the carbon atoms, resulting in the formation of an alcohol.