Using the molar volume in calculations with chemical equations

2 marks · Normal

Calculate the volume, in cm³, of 0.16 g of oxygen gas (O₂) at room temperature and pressure. (Ar: O = 16; molar volume = 24,000 cm³ at rtp)

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120 cm^3 (±1)

Common mistakes: Not using Mr = 32 for O2; Using wrong molar volume

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Marking points

M1 · 1 mark · Correct method to calculate moles of O2 (0.16/32 or correct setup)

A1 · 1 mark · Correct final answer for volume (120 cm³) (follow-through)

Worked solution

First, calculate the Mr of O₂:

Calculate moles:

Calculate the volume at rtp (using molar volume = 24,000 cm³):