relative Formula mass

Question 1

what is relative atomic mass of an element?

Answer 1

the average mass of the isotopes of that element weighted to take into account the abundance of each isotope

Question 2

Relative formula mass Mr

facts

Answer 2

Has no units

never involves big numbers

The RFM of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the formula

Question 3

Calculate the Relative Formula mass of
CH4
if carbon has a Relative atomic mass of 12
and Hydrogen has a R A M of 1

Answer 3

Mr=16
1x carbon 4x hydrogen
1x 12=12
4x 1=4
12+4=16

Relative formula mass =
(first atom x RAM of first atom) + (second atom x RAM of second atom)

Question 4

calculate the relative formula mass of the compound
CaSO4
Ar Ca =40 
Ar S= 32
Ar O = 16

Answer 4

Mr=136

1Ca x 40) + (1S x 32) + (4 O x 16
= 136

Question 5

calculate the relative formula mass of the compound
Mg(OH)2
Ar Mg = 24
Ar O = 16 
Ar H = 1

Answer 5

Mr=58

1Mg x 24) + (2O x 16) + (2H x 1
= 58