Lesson 8: Moles and Empirical Formulae

Question 1

Moles

Relative Atomic Mass

Answer 1

• Describes the mass of a molecule or compound.
• Eg. Cl2 ~> 35.5 + 35.5 = 71

Referred to as relative molecular mass when describing a molecule.

Question 2

Moles

Molecular Mass

Answer 2

• One mole of a substance is its mass in grams.
• Eg(1): 1 mole of Carbon (C) would be 12g.
• Eg(2): 1 mole of Calcium Oxide (CaO) would weigh 56g.

Question 3

Mole Calculations

Formulae

Answer 3

• Moles = concentration × volume
• Moles = volume ÷ 24
• Moles = mass ÷ Mr
• Moles = particles in substance ÷ (6.02 x 10²³)
• Mass = concentration × volume

Moles = mol
Mass = g
Volume = dm³
Concentration = g/dm³

Question 4

Moles

Avogadro’s Constant

Answer 4

The number of chemistry particles in one mole of a substance.

Question 5

Moles

Coefficients

Answer 5

The coefficient in a formula shows the ratio of moles in a substance.

Question 6

Molecular Formula

Description

Answer 6

Number of atoms of each elements in a molecule.

Ethane ~> C2H6

Question 7

Empirical Formula

Description

Answer 7

Simplest whole-number ratio of each element in a compound.

Ethane ~> CH3