1. What is Molecular Mass?

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

2. How is Molecular Mass Calculated?

The molecular mass is calculated by summing the atomic masses of each element multiplied by the number of atoms of that element in the molecule:

For HNO₃ (Nitric Acid):

• 1 Hydrogen atom (H) × 1.008 g/mol
• 1 Nitrogen atom (N) × 14.01 g/mol
• 3 Oxygen atoms (O) × 16.00 g/mol

Calculation: (1.008 × 1) + (14.01 × 1) + (16.00 × 3) = 63.018 g/mol

3. Importance of Molecular Mass

Details: Molecular mass is crucial for stoichiometric calculations, preparing molar solutions, determining empirical formulas, and understanding reaction yields in chemistry.

4. Using the Calculator

Tips: Enter the number of atoms for each element in the molecule. The calculator will sum the atomic masses. Default values show the calculation for HNO₃.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular mass and molar mass?
A: They are numerically identical but molar mass refers to one mole of substance (g/mol) while molecular mass is the mass of one molecule (u).

Q2: How accurate are these atomic masses?
A: These are average atomic masses accounting for natural isotope abundance. For precise work, use exact isotopic masses.

Q3: Can I calculate formula mass for ionic compounds?
A: Yes, the same principle applies to ionic compounds (called formula mass rather than molecular mass).

Q4: Why is molecular mass important in solutions?
A: It's used to prepare molar solutions where 1 mole = molecular mass in grams dissolved in 1 liter of solution.

Q5: How does this relate to the ideal gas law?
A: Molecular mass is used to convert between mass and moles in gas law calculations (PV = nRT).