1. What is Molecular Weight?

Molecular weight (MW) is the sum of the atomic weights of all atoms in a molecule. It's expressed in atomic mass units (u) or grams per mole (g/mol). Accurate molecular weights are essential for stoichiometric calculations in chemistry.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( accurate\_atomic\_masses \) — IUPAC 2013 standard atomic weights
• \( counts \) — Number of each atom in the molecule

Explanation: The calculator parses the chemical formula, looks up each element's atomic mass, multiplies by the atom count, and sums all contributions.

3. Importance of Accurate MW

Details: Precise molecular weights are crucial for:

• Preparing solutions with exact molarity
• Stoichiometric calculations in reactions
• Mass spectrometry analysis
• Polymer chemistry calculations

4. Using the Calculator

Tips:

• Enter chemical formula using standard notation (e.g., C6H12O6 for glucose)
• Element symbols are case-sensitive (Na for sodium, not NA)
• Parentheses and nested formulas are not currently supported

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular weight and molar mass?
A: They are numerically equivalent but molecular weight is dimensionless while molar mass has units of g/mol.

Q2: Why are atomic masses not whole numbers?
A: Atomic masses account for isotopic distributions in natural elements.

Q3: How accurate are these calculations?
A: Using IUPAC standard atomic weights, accuracy is typically within ±0.001 g/mol for small molecules.

Q4: Can I calculate MW for ions?
A: This calculator gives neutral molecule weights. For ions, add/subtract electron mass (0.00055 g/mol per charge).

Q5: What about hydrates or salts?
A: Include water molecules or counterions in the formula (e.g., CuSO4·5H2O).