This worked example covers Worked Examples within Gas Volume for GCSE Chemistry. Topic 19: Gas Volume It is section 4 of 11 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 4 of 11
Practice
20 questions
Recall
20 flashcards
🧮 Worked Examples
Example 1: Moles → Volume
"What volume does 0.5 moles of CO₂ occupy at RTP?"
Volume = moles × 24
Volume = 0.5 × 24
Volume = 12 dm³
"What volume does 0.5 moles of CO₂ occupy at RTP?"
Volume = moles × 24
Volume = 0.5 × 24
Volume = 12 dm³
Example 2: Volume → Moles
"How many moles of oxygen are in 6 dm³ at RTP?"
Moles = Volume ÷ 24
Moles = 6 ÷ 24
Moles = 0.25 mol
"How many moles of oxygen are in 6 dm³ at RTP?"
Moles = Volume ÷ 24
Moles = 6 ÷ 24
Moles = 0.25 mol
Example 3: Gas calculation from equation
"What volume of hydrogen is produced when 0.2 mol of zinc reacts with excess acid?
Zn + 2HCl → ZnCl₂ + H₂"
From equation: 1 mol Zn produces 1 mol H₂
So 0.2 mol Zn produces 0.2 mol H₂
Volume = 0.2 × 24 = 4.8 dm³
"What volume of hydrogen is produced when 0.2 mol of zinc reacts with excess acid?
Zn + 2HCl → ZnCl₂ + H₂"
From equation: 1 mol Zn produces 1 mol H₂
So 0.2 mol Zn produces 0.2 mol H₂
Volume = 0.2 × 24 = 4.8 dm³
Example 4: Mass to volume
"What volume of oxygen (at RTP) is needed to completely burn 8g of methane?
CH₄ + 2O₂ → CO₂ + 2H₂O (Mr of CH₄ = 16)"
Moles CH₄ = 8 ÷ 16 = 0.5 mol
From equation: 1 mol CH₄ needs 2 mol O₂
So 0.5 mol CH₄ needs 1.0 mol O₂
Volume O₂ = 1.0 × 24 = 24 dm³
"What volume of oxygen (at RTP) is needed to completely burn 8g of methane?
CH₄ + 2O₂ → CO₂ + 2H₂O (Mr of CH₄ = 16)"
Moles CH₄ = 8 ÷ 16 = 0.5 mol
From equation: 1 mol CH₄ needs 2 mol O₂
So 0.5 mol CH₄ needs 1.0 mol O₂
Volume O₂ = 1.0 × 24 = 24 dm³