BRAINCAKEPrecise Relative Molecular Mass
The precise relative molecular mass of a molecule is the sum of the precise relative isotopic masses of the atoms in its molecular formula, using the most abundant isotope of each element.
Values usually given in questions:
1H = 1.0078, 12C = 12.0000, 14N = 14.0031, 16O = 15.9949
Method
1. Write each possible molecular formula with the same whole-number Mr.
2. Multiply the number of each type of atom by its precise mass and add them up.
3. Choose the formula whose total matches the measured m/z of the molecular ion.
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
More in Organic Analysis
- Identifying Functional Groups
- Test Tube Tests for Organic Compounds
- High Resolution Mass Spectrometry
- Infrared Spectroscopy
- Bond Vibrations and IR Absorption
- The Fingerprint Region
- Interpreting IR Spectra
- Infrared Radiation and the Greenhouse Effect
All 9 lessons in Organic Analysis · All AQA AS-level Chemistry topics