1. What is Molecular Weight?

Molecular weight (MW) is the sum of the atomic weights of all atoms in a molecule. It's commonly expressed in g/mol (grams per mole) and is essential for stoichiometric calculations in chemistry.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( n_i \) — Number of atoms of element i
• \( MW_i \) — Atomic weight of element i

Explanation: The calculator parses the chemical formula and sums the atomic weights of all constituent atoms.

3. Average vs Monoisotopic Weight

Average Weight: Accounts for natural isotope abundance. Used for most chemical calculations.

Monoisotopic Weight: Uses the mass of the most abundant isotope. Important for mass spectrometry.

4. Using the Calculator

Tips: Enter chemical formula using standard notation (e.g., C6H12O6). Capitalization matters (C for carbon, Ca for calcium).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular weight and molar mass?
A: They are numerically identical but molar mass is the mass of one mole of substance (g/mol), while molecular weight is dimensionless.

Q2: How accurate are these calculations?
A: Accuracy depends on the atomic weight values used. For precise work, consult IUPAC's latest atomic weights.

Q3: Can I calculate weights for modified amino acids?
A: This calculator handles simple formulas. For complex molecules, use specialized software.

Q4: Why are there two weight types?
A: Average weight is used for bulk chemistry, monoisotopic for mass spectrometry where isotope peaks are resolved.

Q5: How should I enter hydration states?
A: Include water molecules in the formula (e.g., CuSO4·5H2O as CuSO4H10O5).