1. What is Exact Mass?

Exact mass is the calculated mass of an ion or molecule based on the most abundant isotopes of each element. It differs from molecular weight which uses average atomic masses.

2. How Does the Calculator Work?

The calculator uses the exact mass formula:

Where:

• \( \text{Atomic Mass} \) — Mass of the most abundant isotope (amu)
• \( \text{Count} \) — Number of atoms in the molecule

Explanation: The equation sums the mass contributions of all atoms in the molecule using the most abundant isotope for each element.

3. Importance of Exact Mass Calculation

Details: Exact mass is crucial in mass spectrometry for identifying molecular formulas, distinguishing between compounds with similar nominal masses, and confirming molecular structures.

4. Using the Calculator

Tips: Enter the atomic mass of the most abundant isotope in amu and the number of atoms. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between exact mass and molecular weight?
A: Exact mass uses isotopic masses while molecular weight uses average atomic masses from the periodic table.

Q2: How precise should the atomic mass be?
A: For most applications, 4 decimal places is sufficient. High-resolution mass spectrometry may require more precision.

Q3: Can I calculate exact mass for multiple elements?
A: This calculator handles one element at a time. For molecules, you would sum the exact masses of all constituent atoms.

Q4: Where can I find isotopic masses?
A: Isotopic masses are available in chemistry references and online databases like NIST.

Q5: Why is exact mass important in mass spectrometry?
A: It allows distinguishing between compounds with the same nominal mass but different elemental composition.