Using the molar volume in calculations with chemical equations

3 marks · Normal

A student needs to calculate the mass of carbon dioxide produced when 48,000 cm³ of carbon dioxide is collected at room temperature and pressure. Explain the steps, including the formulae needed, to calculate the mass of carbon dioxide produced. (Ar: C = 12, O = 16; molar volume = 24,000 cm³ at rtp)

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

Must show: Step 1: Use volume and molar volume to calculate moles of CO2., Step 2: Calculate Mr of CO2., Step 3: Use moles and Mr to calculate the mass.

Common mistakes: Forgetting to calculate Mr correctly; Not explaining all steps

Show mark scheme and worked solution

Marking points

M1 · 1 mark · States or implies using moles = volume / molar volume correctly.

M2 · 1 mark · Describes how to find the Mr of CO2 (C + 2 × O = 12 + 2×16 = 44).

M3 · 1 mark · Describes mass = moles × Mr with correct substitution.

Worked solution

Step 1: Calculate the number of moles of CO₂ using:

Step 2: Calculate Mr of CO₂:

Step 3: Calculate the mass using: