How grams → moles works
The mole links the mass of a substance to the number of particles. To convert, you must know its molar mass in g/mol.
moles = mass (g) ÷ molar mass (g/mol)
Example: 36.03 g H₂O ÷ 18.015 g/mol = 2.000 mol H₂O
Where to get molar mass
From the chemical formula:
- Write the formula: e.g. H₂O
- Take atomic masses from the periodic table: H = 1.008, O = 16.00
- Multiply and add: 2×1.008 + 16.00 = 18.016 ≈ 18.015 g/mol
Reverse: moles → grams
mass (g) = moles × molar mass (g/mol)
Example: 0.25 mol NaCl × 58.44 g/mol = 14.61 g NaCl
FAQ
1. Do I need Avogadro’s number?
Not for mass ↔ moles. Avogadro’s number is used when you want the number of molecules/atoms from moles.
2. What if I only know chemical name?
Look up its formula and molar mass, then enter it here.
3. Why is my answer different from class notes?
Teachers sometimes round molar masses (e.g. use 58.5 instead of 58.44). Use the same rounding to match their answer.
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
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Formula (extracted text)
moles = mass (g) ÷ molar mass (g/mol) Example: 36.03 g H₂O ÷ 18.015 g/mol = 2.000 mol H₂O
Formula (extracted text)
mass (g) = moles × molar mass (g/mol) Example: 0.25 mol NaCl × 58.44 g/mol = 14.61 g NaCl
Variables and units
- No variables provided in audit spec.
Sources (authoritative):
- NIST — Weights and measures — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/weights-and-measures - NIST — SI units — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/owm/metric-si/si-units
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
- Initial audit spec draft generated from HTML extraction (review required).
- Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
- Confirm sources are authoritative and relevant to the calculator methodology.