1. What is Molecular Mass?

Molecular mass (or molecular weight) is the sum of the atomic masses of all the atoms in a molecule. It's expressed in atomic mass units (u) or grams per mole (g/mol).

2. How to Calculate Molecular Mass

The molecular mass is calculated using the formula:

Where:

• Atomic Mass — The mass of a single atom of each element (from periodic table)
• Count — The number of atoms of each element in the molecule

Example: For water (H₂O):

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

3. Importance of Molecular Mass

Details: Molecular mass is crucial for:

• Stoichiometric calculations in chemical reactions
• Preparing solutions with specific molar concentrations
• Determining empirical and molecular formulas
• Gas law calculations

4. Using the Calculator

Instructions:

1. Enter element symbols (comma separated) like "H, C, O"
2. Enter corresponding counts (comma separated) like "2, 6, 1" for C₂H₆O
3. Click "Calculate" to get the molecular mass

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular mass and molar mass?
A: They are numerically equal but molecular mass is for single molecules (in u) while molar mass is for one mole of substance (in g/mol).

Q2: How do I calculate molecular mass for ionic compounds?
A: For ionic compounds, we calculate formula mass (sum of atomic masses of all atoms in the formula unit) using the same method.

Q3: What if my compound has parentheses or dots?
A: For hydrates (e.g., CuSO₄·5H₂O), multiply the water part separately and add to the main formula mass.

Q4: Where can I find accurate atomic masses?
A: Use IUPAC's standard atomic weights from the periodic table. This calculator uses commonly accepted values.

Q5: Why is my calculated value slightly different from published values?
A: Published values account for natural isotope abundance. This calculator uses average atomic masses.

Molecular Mass Calculator© - All Rights Reserved 2025