Relative Molecular Mass and Relative Formula Mass Flashcards
1
Q
What does Mr look at the relative mass of?
A
different molecules (simple covalent molecules)
2
Q
What is Mr?
A
the mass of a molecule, relative to 1/12th the mass of an atom of carbon-12
3
Q
What is the units for Mr?
A
g.mol^-1
4
Q
What can you also calculate Mr with?
A
elements and compounds
5
Q
How do you calculate Mr?
A
it is the sum (added up) of the Ar values of the elements in the molecule
e.g. to find the Mr of Hv2, you look at the Ar, and add it to the number of molecules of that element - so 1+1 = 2.0g.mol^-1
6
Q
What is the RFM?
A
The mass of the formula, relative to 1/12th mass of an atom of carbon-12
7
Q
What is the RFM used for?
A
giant iconic compounds (salts)
8
Q
How do you calculate the RFM?
A
you add up the Ar values together to give you the RFM
e.g.
NaCl = 23 + 35.5 = 58.5g.mol^-1
