1. What is Molecular Weight?

Molecular weight (MW), also called molecular mass, 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).

2. How to Calculate Molecular Weight

The molecular weight is calculated using the formula:

Where:

• \( MW \) — Molecular weight (g/mol)
• \( atomic\_masses \) — Atomic weights of each element (g/mol)
• \( counts \) — Number of atoms of each element in the molecule

Example: For water (H₂O):

• 2 Hydrogen atoms: 2 × 1.008 g/mol = 2.016 g/mol
• 1 Oxygen atom: 1 × 15.999 g/mol = 15.999 g/mol
• Total MW = 2.016 + 15.999 = 18.015 g/mol

3. Importance of Molecular Weight

Details: Molecular weight is crucial for stoichiometric calculations, preparing solutions with specific molarity, and determining physical properties like boiling point and density.

4. Using the Calculator

Tips: Enter elements and their counts in the format "ElementCount" separated by spaces (e.g., "C6 H12 O6" for glucose). The calculator will sum the atomic weights of all atoms in the molecule.

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 expressed in grams per mole (g/mol) while molecular weight is dimensionless.

Q2: How do I calculate MW for ionic compounds?
A: Use the same method, summing the atomic weights of all atoms in the formula unit.

Q3: Where can I find atomic weights?
A: Standard atomic weights are published by IUPAC and available in periodic tables.

Q4: How accurate are these calculations?
A: They're based on average atomic weights. For precise work, use isotopic composition.

Q5: Can this calculator handle complex molecules?
A: Yes, as long as you correctly specify all elements and their counts.