1. What is Molar Mass?

Molar mass is the mass of one mole of a substance (chemical element or chemical compound). For water (H₂O), it's the combined atomic weights of two hydrogen atoms and one oxygen atom.

2. How is Molar Mass Calculated?

The molar mass is calculated by summing the atomic masses of all atoms in a molecule:

For water (H₂O):

• Hydrogen (H): 1.008 g/mol × 2 atoms = 2.016 g/mol
• Oxygen (O): 15.999 g/mol × 1 atom = 15.999 g/mol
• Total: 2.016 + 15.999 = 18.015 g/mol

3. Importance of Molar Mass

Details: Molar mass is fundamental in chemistry for converting between grams and moles, preparing solutions, stoichiometric calculations, and understanding gas laws.

4. About Water Vapor

Details: Water vapor is the gaseous phase of water. Its molar mass (18.015 g/mol) is crucial for calculations in atmospheric science, humidity measurements, and industrial processes.

5. Frequently Asked Questions (FAQ)

Q1: Why is water's molar mass important?
A: It's essential for calculating humidity, partial pressures in gas mixtures, and in chemical reactions involving water vapor.

Q2: Does molar mass change with state?
A: No, water's molar mass is the same whether it's solid, liquid, or gas (18.015 g/mol).

Q3: How does this compare to dry air?
A: Dry air has an average molar mass of about 28.97 g/mol, making water vapor less dense than dry air at the same conditions.

Q4: Why is water vapor's molar mass less than air?
A: Because H₂O molecules (18 g/mol) are lighter than the main components of air (N₂ = 28 g/mol, O₂ = 32 g/mol).

Q5: How accurate is this value?
A: The value accounts for natural isotopic distribution. For precise work, exact isotopic composition may be considered.