Moles calculator
Type a chemical formula and one quantity you know. The calculator shows the relative formula mass with working, then the amount in moles, the mass, the volume of gas at r.t.p. and the concentration.
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Mr of CaCO3 = 100
1 × Ca (40) + 1 × C (12) + 3 × O (16) = 100
- Amount: 0.25 mol
- Mass: 25 g
- Gas volume at r.t.p.: 6 dm³ (6000 cm³)
- Particles: 1.50 × 10²³
- If dissolved to make 250 cm³: 1 mol/dm³ (100 g/dm³)
Answers to 3 significant figures, using the Ar values on the IGCSE data sheet and 24 dm³ per mole of gas at r.t.p.
The formulas it uses
- moles = mass ÷ Mr
- gas volume (dm³) = moles × 24 (at room temperature and pressure)
- concentration (mol/dm³) = moles ÷ volume (dm³), where dm³ = cm³ ÷ 1000
- particles = moles × 6.02 × 10²³
Use it to check, not to skip
In the exam you must show the working. Do the calculation yourself first, then use this tool to check your Mr and your answer.
Questions students ask
How do I enter brackets and water of crystallisation?
Type Ca(OH)2 for calcium hydroxide and CuSO4.5H2O for hydrated copper(II) sulfate.
Which Ar values are used?
The values on the IGCSE Chemistry data sheet, for example Cl = 35.5 and Cu = 64.