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. Exact mass is particularly important in mass spectrometry.

2. How Does the Calculator Work?

The calculator uses the exact mass formula:

Where:

• \( EM \) — Exact mass in unified atomic mass units (u)
• \( A_i \) — Number of atoms of element i
• \( M_i \) — Isotopic mass of element i (most abundant isotope)

Explanation: The calculator parses the chemical formula, identifies each element and its count, then sums the exact masses of all atoms in the molecule.

3. Importance of Exact Mass

Details: Exact mass is crucial in mass spectrometry for identifying compounds. The high resolution of modern instruments can distinguish between compounds with very similar molecular weights.

4. Using the Calculator

Tips: Enter the chemical formula using standard notation (e.g., C6H12O6 for glucose). Case matters - element symbols start with uppercase followed by lowercase (Na for sodium, not NA or na).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between exact mass and molecular weight?
A: Exact mass uses the most abundant isotope of each element, while molecular weight uses the average atomic mass weighted by natural isotope abundance.

Q2: Why is exact mass important in mass spectrometry?
A: High-resolution mass spectrometers can measure mass-to-charge ratios precisely enough to distinguish between compounds with similar but not identical masses.

Q3: How accurate is this calculator?
A: The calculator uses standard isotopic masses with 6 decimal places. For extremely precise work, consult the most recent IUPAC tables.

Q4: What elements are supported?
A: The calculator currently supports H, C, N, O, F, P, S, Cl, Br, and I. More elements can be added as needed.

Q5: Can I use parentheses or dots in formulas?
A: Currently only simple formulas are supported. Hydrates and complex ions are not yet implemented.