1. What is Molecular Weight?

Molecular weight (MW) is the sum of the atomic weights of all atoms in a molecule. It's expressed in atomic mass units (u) or grams per mole (g/mol). The PNNL formula calculates this by summing the standard atomic weights of each element in the chemical formula.

2. How Does the Calculator Work?

The calculator uses the PNNL formula:

Where:

• \( MW \) — Molecular weight in g/mol
• \( \sum \) — Sum of all atomic masses in the formula
• Atomic masses — Standard atomic weights from IUPAC

Explanation: The calculator parses the chemical formula, identifies each element and its count, then sums their atomic weights.

3. Importance of Molecular Weight

Details: Molecular weight is crucial for stoichiometric calculations, preparing molar solutions, determining reaction yields, and in various analytical techniques like mass spectrometry.

4. Using the Calculator

Tips: Enter the chemical formula using standard notation (e.g., H2O for water, C6H12O6 for glucose). Case matters - element symbols start with uppercase letters.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular weight and molar mass?
A: They are numerically equivalent but molecular weight refers to single molecules while molar mass refers to one mole of substance.

Q2: How accurate is this calculator?
A: It uses standard atomic weights. For precise work, use isotopic-specific weights if needed.

Q3: Does it work for complex formulas?
A: Yes, it handles formulas with multiple elements and subscripts (e.g., Ca3(PO4)2).

Q4: What about hydrates or salts?
A: Include water molecules or counterions in the formula (e.g., CuSO4·5H2O).

Q5: Can I get the weight of individual elements?
A: This calculator provides total molecular weight only.