1. What is Molecular Weight?

Molecular weight (MW) is the sum of the atomic weights of all atoms in a molecule. For water (H₂O), it's calculated by adding the atomic weights of two hydrogen atoms and one oxygen atom.

2. Water Molecular Structure

Water consists of two hydrogen atoms covalently bonded to one oxygen atom in a bent molecular geometry with a bond angle of approximately 104.5°.

3. Calculation Method

The molecular weight of water is calculated as:

Where:

• Atomic Weight of Hydrogen (H) = 1.00794 g/mol
• Atomic Weight of Oxygen (O) = 15.9994 g/mol
• Water MW = (2 × 1.00794) + 15.9994 = 18.01528 g/mol

4. Using the Calculator

Tips: Enter the number of water molecules you want to calculate the total molecular weight for. The calculator will multiply the standard water MW (18.015 g/mol) by your input number.

5. Frequently Asked Questions (FAQ)

Q1: Why is water's molecular weight important?
A: It's essential for stoichiometric calculations in chemistry, preparing solutions, and understanding water's physical properties.

Q2: Does the molecular weight vary with isotopes?
A: Yes, this calculation uses average atomic weights. Heavy water (D₂O) with deuterium has a higher MW (about 20 g/mol).

Q3: How precise is this calculation?
A: The calculator uses standard atomic weights with 4 decimal places for precision in most applications.

Q4: Can I calculate for fractional molecules?
A: While mathematically possible, physically you can't have a fraction of a molecule in reality.

Q5: How does temperature affect molecular weight?
A: Temperature doesn't affect the actual molecular weight, but it can affect apparent weight measurements in gases due to density changes.