JAMB Chemistry Past Questions & Answers - Page 5

21.

At 2.0 atm pressure, the volume of a gas is 4.0 L. If the pressure is reduced to 1.0 atm while keeping the temperature constant, what will be the new volume of the gas?

A.

2.0 L

B.

6.0 L

C.

8.0 L

D.

4.0 L

Correct answer is C

According to Boyle's law, when the temperature is constant, the initial pressure multiplied by the initial volume is equal to the final pressure multiplied by the final volume. Mathematically, P1V1 = P2V2, where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume, respectively. Using the given values:
(2.0 atm) * (4.0 L) = (1.0 atm) * (V2)
Solving for V2:
V2 = (2.0 atm * 4.0 L) / (1.0 atm) = 8.0 L

22.

Which functional group is present in alkanals?

A.

Carbonyl group (C=O)

B.

Hydroxyl group (-OH)

C.

Alkyl group (-R)

D.

Carboxyl group (-COOH)

Correct answer is A

The carbonyl group (C=O) is the functional group present in alkanals. It consists of a carbon atom double-bonded to an oxygen atom.

23.

What happens when alkanoic acids react with alcohols in the presence of an acid catalyst?

A.

Saponification

B.

Esterification

C.

Polymerization

D.

Hydrolysis

Correct answer is B

When alkanoic acids react with alcohols in the presence of an acid catalyst, esterification occurs. This chemical reaction forms esters and water.

24.

Which of the following metals is commonly alloyed with copper to make brass?

A.

Iron

B.

Nickel

C.

Aluminum

D.

Zinc

Correct answer is D

Brass is an alloy made by combining copper with zinc. It is a versatile material with a golden appearance and is used in various applications, including musical instruments, plumbing fittings, and decorative items.

25.

What is the atomic number of aluminium?

A.

13

B.

26

C.

14

D.

12

Correct answer is A

The atomic number of an element is the number of protons in the nucleus of an atom of that element. The atomic number of aluminium is 13, which means it has 13 protons in its nucleus.