Mole Flashcards
What is the Avogadro number?
6.023*10^23
What is a mole?
A fixed amount of particles
Why do we use the mole?
To compare different chemicals
What is the relative atomic mass?
This is the average mass of an atom compared with 1/12 of the mass of a carbon-12 atom
Why do we use carbon-12 atom?
We use it as comparison because the mass number is very accurate.
Carbon has a high abundance
What is a molecular ion?
When the whole molecule loses one electron
What is relative molecular mass?
The average mass if a molecule compared with 1/12th of the mass of a carbon-12 atom
Why does RMM occur?
When compounds are ionised in mass spectrometer, loss of electron can weaken the bonds. Molecule likely to fragment and split up. Other smaller ions also produced which cause number of peaks on spectrum
How to calculate RMM?
It is a chemical with the highest value of m/z when none of the chemical has fragmented
How to calculate RAM?
(Abundancem/z)+(abundancem/z) divided by total abundance
Why does half values of m/z occur?
Some atoms occasionally lose 2 electrons in the ionisation chamber of the mass spectrometer
Causes a 2+ charge
Why is the m/z value for a species half the number of the isotopes?
Due to the 2+ charge
Extremely rare so only a small peak formed
Do we use the figures of small peak when calculating RAM?
No
Mg exists as 3 isotopes with mass numbers 24, 25, 26
What species produce peak at m/z=12?
24 mg 2+
