relative masses, percentage composition of compounds

Question 1

relative atomic mass (Ar)

Answer 1

given in the periodic table (bottom number)

Question 2

relative molecular mass (Mr)

Answer 2

sum of Ar of all the elements

Question 3

relative formula mass (Mr)

Answer 3

sum of Ar of all the ions

Question 4

do Ar and Mr have units?

Answer 4

no

Question 5

what’s another way of expressing Ar and Mr?

Answer 5

molar mass. units is g mol-1

Question 6

percentage by mass of an element in a compound

Answer 6

(Ar of element x no. of atoms in formula) / Mr of compound x 100%