calculate the concentraion of Na --- plz help?

Question

A 2.1347g of Na3RhCl6.12H2O was dissolved in 500cm3 of water

a) calculate the concentration of Na in the solution in mol dm-3

b) calculate the concentration of Rh in the solution in ppm

Answer 1

The molar mass of Rh: 102.9055g/mol
The molar mass of Na3RhCl6.12H2O: 600.77g/mol

2.1347g of Na3RhCl6.12H2O = 0.0035533 mol ==> 0.0071065M ==> 0.0213 M Na+ = 0.0213 (mol/dm3)

(102.9055/600.77)*(2.1347/(500+2.1347)) = 728x10^-6 = 728ppm (in wt.)