Quick answer: Amount of substance n equals mass m divided by molar mass M: n = m/M. With m in grams and M in grams per mole, the result is in moles. Particle count is n times Avogadro's constant.
Worked example
Find the amount of CO₂ in 22 g, using C = 12 and O = 16 g/mol.
- M(CO₂) = 12 + 2×16 = 44 g/mol.
- n = 22/44 = 0.5 mol.
- Molecule count is approximately 0.5×6.022×10²³ = 3.011×10²³.
Check the result
Multiplying 0.5 mol by 44 g/mol returns 22 g.
Stuck on a question? Ask it here and get a step-by-step answer in seconds — pay only per answer, no subscription. Ask your doubt now →
Common mistake to avoid
One mole of CO₂ molecules contains two moles of oxygen atoms. Distinguish molecules, atoms and ions, and use consistent mass units.
Try it yourself
1. Find moles in 18 g of water using M = 18 g/mol. 2. Find mass of 0.25 mol CO₂.
Answers and reasoning
1. 18/18 = 1 mol. 2. 0.25×44 = 11 g.
Need help with your own attempt? Ask a study question. AI answers require an account and paid credits. Check important steps with your textbook or teacher.
Stuck on a question? Ask it here and get a step-by-step answer in seconds — pay only per answer, no subscription. Ask your doubt now →