LIMITLESS EXAM: Gas Volume

Cambridge IGCSE Chemistry 0620 | Topic 3.3.2

Paper Type

Paper 4: Extended Theory

Total Questions

15 Questions

Focus

Molar Volume Calculations

Essential Formula

One mole of any gas occupies 24 dm³ at r.t.p.

(room temperature and pressure: 25°C, 1 atmosphere)

Volume → Moles

moles = volume (dm³) ÷ 24

Moles → Volume

volume = moles × 24 dm³

SECTION A: The Molar Volume Constant

Questions 1-5 | Knowledge Recall

Q1[1 mark]

State the volume occupied by one mole of any gas at room temperature and pressure (r.t.p.).

Q2[2 marks]

Define what is meant by "room temperature and pressure" (r.t.p.).

Q3[1 mark]

Does the molar volume of 24 dm³ apply only to oxygen, or to all gases?

Q4[2 marks]

Explain why we specify "at r.t.p." when stating the molar volume.

Q5[1 mark]

At standard temperature and pressure (s.t.p.: 0°C, 1 atm), what volume does one mole of gas occupy?

SECTION B: Volume ⟷ Moles Conversions

Questions 6-10 | Calculation Skills

Q6[2 marks]

Calculate the number of moles in 48 dm³ of oxygen gas at r.t.p.

Q7[2 marks]

Calculate the volume occupied by 0.5 moles of chlorine gas (Cl₂) at r.t.p.

Q8[3 marks]

A sample of carbon dioxide gas has a volume of 120 cm³ at r.t.p. Calculate the number of moles of CO₂.

Q9[2 marks]

Calculate the volume in cm³ of 0.25 moles of nitrogen gas (N₂) at r.t.p.

Q10[3 marks]

72 dm³ of hydrogen gas (H₂) is collected at r.t.p. Calculate the mass of this hydrogen. [Mr(H₂) = 2]

SECTION C: Reacting Gas Volumes

Questions 11-15 | Equation Stoichiometry

Q11[2 marks]

Hydrogen burns in oxygen according to the equation:

2H₂(g) + O₂(g) → 2H₂O(l)

What volume of oxygen is needed to react completely with 50 cm³ of hydrogen?

Q12[3 marks]

Nitrogen reacts with hydrogen to form ammonia:

N₂(g) + 3H₂(g) → 2NH₃(g)

Calculate the volume of hydrogen needed to react with 20 cm³ of nitrogen.

Q13[3 marks]

Carbon monoxide burns in oxygen:

2CO(g) + O₂(g) → 2CO₂(g)

What volume of carbon dioxide is produced when 100 cm³ of carbon monoxide burns completely?

Q14[4 marks]

30 cm³ of methane (CH₄) is burned in 100 cm³ of oxygen:

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

Calculate the volume of oxygen that remains unreacted after complete combustion.

Q15[5 marks]

Propane (C₃H₈) burns in oxygen:

C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l)

120 dm³ of propane burns completely at r.t.p.

Calculate the volume of carbon dioxide produced at r.t.p.

Examiner's Final Tips

1. Units Matter: Always use dm³ in the formula. Convert cm³ → dm³ first (÷1000).

2. Show Your Working: Even if you get the wrong answer, you get method marks for the correct formula.

3. Volume Ratios = Mole Ratios: For gases, just use the coefficients from the balanced equation.

4. The Magic Number: 24 dm³ is your best friend. Memorize it!

5. Multi-Step Questions: Break them down. Volume → moles → stoichiometry → moles → volume.

Cambridge IGCSE Chemistry (0620)

Topic 3.3.2: The Molar Volume of a Gas

Limitless Chemistry Protocol V2.0 | Exam Component

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