What are the proportions by mass of the elements in the compound Sodium Sulfate, Na_2SO_4?

Question

step by step

Answer 1

molar mass of Na2SO4= 142g/mol
proportion by mass of sodium=46/142*100= 32.4%
of sulphur= 22.5%
of oxygen= 47.1%

Answer 2

(2 x 23)/142 x 100% for Na, because there are two of them, and 142 is the Mr of the compound and 23 is the Ar for Na.

Similarly, (1 x 32)142 x 100% for S and (4 x 16)/142 x 100% for O.