Secondary 3 Mole Calculations Worksheet

Calculate the relative molecular mass of ethanoic acid (CH₃COOH)

Answer explanation

Mr of CH₃COOH = 12 + 3(1) + 12 + 2(16) +1

Calculate the number of moles in 12 g of magnesium. (Ar of Mg = 24)

• 0.5 moles

• 1 mole

• 0.25 moles

• 2 moles

Answer explanation

n = mass/Mr

= 12 g/24

= 0.5 moles

How many moles are there in 88 g of carbon dioxide (CO₂)? (Mr of CO₂ = 44)

• 2.0 moles

• 0.5 moles

• 44 moles

• 4.0 moles

Answer explanation

n = mass / Mr

= 88 g/44

= 2.0 moles

What is the mass of 0.5 moles of sodium hydroxide (NaOH)? (Mr of NaOH = 40)

Include units

Answer explanation

mass = n × Mr

= 0.5 × 40

= 20 g

What volume of hydrogen gas is produced when 0.25 moles of hydrogen is collected?

• 6.0 dm³

• 2.5 dm³

• 12.0 dm³

• 1.0 dm³

Answer explanation

Volume of gas = n × 24 dm³

= 0.25 × 24 dm³

= 6.0 dm³

How many moles of oxygen are present in 48 dm³ of oxygen gas?

• 2.0 moles

• 1.0 mole

• 0.5 moles

• 4.0 moles

Answer explanation

n = Volume of gas/24 dm³

= 48/24 dm³

= 2.0 moles

What volume will 0.75 moles of nitrogen gas occupy at room temperature?

• 18.0 dm³

• 11.2 dm³

• 22.4 dm³

• 33.6 dm³

Answer explanation

Volume of gas

= 0.75 × 24

= 18.0 dm³

A solution contains 0.2 moles NaCl in 250 cm³. Find its concentration.

• 0.8 mol/dm³

• 0.2 mol/dm³

• 0.5 mol/dm³

• 0.0008 mol/dm³

Answer explanation

250 cm³ = 0.25 dm³,

concentration = no of moles / volume of solution in dm³

= 0.2/0.25

= 0.8 mol/dm³

How many moles of HCl in 500 cm³ of 0.4 mol/dm³ HCl solution?

• 0.2 moles

• 0.1 moles

• 0.4 moles

• 0.05 moles

Answer explanation

500 cm³ = 0.5 dm³,

no of moles = Concentration ×Volume of solution

= 0.4×0.5

= 0.2 moles

What volume of 0.5 mol/dm³ KOH contains 0.05 moles of KOH?

• 100 cm³

• 50 cm³

• 200 cm³

• 500 cm³

Answer explanation

Volume = no of moles /Concentration

= 0.05/0.5

= 0.1 dm³

= 100 cm³