Data Source and Methodology
Authoritative data: IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), Standard Atomic Weights (latest tables), and the SI redefinition of the Avogadro constant (2019). Primary references:
- IUPAC Periodic Table and CIAAW Standard Atomic Weights (2021): https://iupac.org/what-we-do/periodic-table-of-elements/
- Commission on Isotopic Abundances and Atomic Weights: https://ciaaw.org/standard-atomic-weights.htm
- SI Brochure, 9th Edition (BIPM): Exact Avogadro constant N_A = 6.02214076 × 10^23 mol^-1: https://www.bipm.org/en/publications/si-brochure
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
The Formula Explained
Amount–mass relationship:
Inline: \( m = n \times M \) and \( n = \dfrac{m}{M} \)
Display:
\[ m\;[\mathrm{g}] = n\;[\mathrm{mol}] \times M\;[\mathrm{g/mol}] \]
Where the molar mass M is the sum of each element’s atomic weight multiplied by its stoichiometric coefficient in the formula:
\[ M = \sum_{i} a_i \, A_r(i) \]
Glossary of Variables
- Chemical formula: The composition of the substance (e.g., C6H12O6, CuSO4·5H2O).
- Molar mass (M): Mass per mole of substance, in g/mol, derived from IUPAC atomic weights.
- Amount of substance (n): The quantity in moles (mol).
- Mass (m): The quantity in grams (g).
- Avogadro constant (N_A): Exact number of entities per mole, \( 6.02214076 \times 10^{23}\,\mathrm{mol^{-1}} \).
- Decimal places: Rounding precision for displayed results.
How It Works: A Step-by-Step Example
- Enter the formula C6H12O6 (glucose). The tool computes the molar mass: \( M = 6\cdot 12.011 + 12\cdot 1.008 + 6\cdot 15.999 = 180.156\ \mathrm{g/mol} \).
- Select “Moles → Grams” and input \( n = 2.50\ \mathrm{mol} \).
- Apply the formula \( m = n \times M \): \( m = 2.50 \times 180.156 = 450.39\ \mathrm{g} \).
- The result shows 450.390 g if decimal places are set to 3.
FAQ
What is the difference between atomic mass and molar mass?
Atomic mass is the mass of a single atom (in unified atomic mass units, u), while molar mass is the mass per mole of a substance (g/mol). Numerically they are related via Avogadro’s constant.
Do I need to enter a formula?
No. You may toggle “Enter manually” and supply a known molar mass. Entering a formula helps the tool compute the molar mass for you.
Are hydrates supported?
Yes. Use a dot (· or .), e.g., CuSO4·5H2O. Parentheses and nested groups are also supported.
How many decimal places should I use?
Choose a level appropriate for your measurement uncertainty and reporting standards. For classroom work, 2–4 decimals are common.
What if my formula contains a charge?
Charges (e.g., SO4^2−) do not affect molar mass and are ignored by the parser.
Why might different sources show slightly different molar masses?
Atomic weights are conventional averages that reflect natural isotopic distributions and may be reported with different rounding or recommended intervals. This tool uses IUPAC standard values.