What is the mass of Na2SO4 needed to make 2.5 L of 2.0 M solution?

how man molecules are there in 450 grams of Na2SO4.

the simple formula to determine of mole is NO OF MOL= GIVEN MASS IN gm/MOL:MASS OF COMP: , AND IMOL = 6.02X1023 . SO, 19. 077X1023 molecules are present in 450 grams of Na2SO4.