CXC - Caribbean Examinations Council Chemistry: The Mole Concept Questions and Answers

Question 1

What does Avogadro's constant represent?

Accepted Answer

The number of particles (atoms, molecules, or ions) in one mole of a substance.

Answer

The volume occupied by one mole of any gas at standard temperature and pressure.

Answer

The mass in grams of one mole of the carbon-12 isotope.

Answer

The total number of protons and neutrons in the nucleus of a carbon-12 atom.

Question 2

A student needs to calculate the number of moles in a 50 g sample of calcium carbonate (CaCO₃). What is the correct value? (Relative atomic masses: Ca = 40, C = 12, O = 16)

Accepted Answer

0.5 moles

Answer

2.0 moles

Answer

1.0 mole

Answer

100 moles

Question 3

Which of the following describes the volume occupied by one mole of any gas at room temperature and pressure (RTP)?

Accepted Answer

24.0 dm³

Answer

It depends on the molar mass of the gas.

Answer

22.4 dm³

Answer

6.02 x 10²³ dm³

Question 4

What is the mass of 1.2 x 10²⁴ molecules of sulfur dioxide (SO₂)? (Relative atomic masses: S = 32, O = 16; Avogadro's constant = 6.0 x 10²³ mol⁻¹)

Accepted Answer

128 g

Answer

64 g

Answer

32 g

Answer

256 g

Question 5

Which of the following statements correctly defines the mole?

Accepted Answer

The amount of substance that contains the same number of particles as there are atoms in exactly 12 g of carbon-12.

Answer

The mass of a substance that contains 6.02 x 10²³ grams of particles.

Answer

The relative atomic mass of a substance expressed in grams.

Answer

The volume of a substance that contains exactly 24 dm³ of particles at RTP.

Question 6

A chemical reaction produces 4.8 dm³ of carbon dioxide gas (CO₂) at Room Temperature and Pressure (RTP). How many moles of CO₂ were produced? (Molar volume of a gas at RTP = 24.0 dm³/mol)

Accepted Answer

0.2 moles

Answer

0.5 moles

Answer

5.0 moles

Answer

2.0 moles