1. What is Molecular Weight?

Molecular weight (MW), also known as molecular mass, is the sum of the atomic weights of all atoms in a molecule. It's expressed in atomic mass units (amu) or grams per mole (g/mol).

2. How is Molecular Weight Calculated?

The molecular weight is calculated using the formula:

Where:

• \( atomic\_masses \) — The mass of each individual atom (g/mol)
• \( counts \) — The number of each type of atom 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 molecular weight = 2.016 + 15.999 = 18.015 g/mol

3. Importance of Molecular Weight

Details: Molecular weight is crucial for:

• Determining stoichiometry in chemical reactions
• Preparing solutions with specific molar concentrations
• Understanding physical properties like boiling point and density
• Mass spectrometry and other analytical techniques

4. Using the Calculator

Instructions: Enter elements and their counts in the format "Element:Count" separated by commas. For example:

• Water (H₂O): "H:2, O:1"
• Glucose (C₆H₁₂O₆): "C:6, H:12, O:6"
• Sulfuric acid (H₂SO₄): "H:2, S:1, O:4"

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular weight and molar mass?
A: They are numerically identical but molar mass refers specifically to the mass of one mole of a substance.

Q2: How do I calculate molecular weight for ionic compounds?
A: The same way - sum the atomic masses of all atoms in the formula unit.

Q3: Why are atomic masses not whole numbers?
A: Atomic masses account for natural isotopic abundance of each element.

Q4: Can this calculator handle complex molecules?
A: Yes, as long as you enter all elements and their counts correctly.

Q5: Where can I find atomic masses not listed here?
A: Consult the periodic table or IUPAC atomic weights database.