Mr is relative formula mass, it is the mass of a molecule. Its calculation is (number of that element in the molecule x relative atomic mass) + (number of that element in the molecule x relative atomic mass)
Ar is relative atomic mass, it is the average mass of an atom of a specific element. It is calculated by doing (% of isotope x mass of isotope) + (% of isotope x mass of isotope) over 100.
Hannah, Could you give me an example please?
ReplyDeleteCl is 25% 35 and 75% 37 so
Delete(25 x 35) + (75 x 37) over 100=
(875) + (2775) over 100=
3650 / 100= 36.5
So the Ar of Cl is 36.5
and the Ar of H is 1
to work out the Mr of HCl
(1 x 1) + (1 x 36.5)=
1 + 36.5=
37.5
The percentage of isotopes in a sample of Cl atoms is actually the other way around:
Delete25% Cl37 atoms 75% Cl35 atoms
So the Ar of Chlorine is actually 35.5
Thanks for everything you've done Hanna, amazing resource
thuck up
Deleteokay im done.
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Deletedon't you mean it is the mass of a compound as a molecule can just be one element but a compound is at least two different elements
ReplyDelete
ReplyDeleteokay
done