Answer
a. 3.44 g Na
b. 19.0 g S
c. the mass of 2.78 mol $CH_{2}Cl_{2}$ is 236 g
d. the mass of 38 mol ${(NH_{4}})_2S$ is 2.59 x$10^{3}$ g
Work Step by Step
Strategy: We have to convert moles to mass. So the conversion factor is Molar mass/ 1 mol.
a. Mass of 0.15 mol Na.
Molar mass of Na is 22.9 g/mol. Therefore :
0.15 mol Na x $\frac{22.9 g Na}{ 1 mol Na}$ = 3.44 g Na
b. Mass of 0.594 mol S.
Molar mass of S is 32.0 g/mol. Therefore :
0.594 mol S x $\frac{32.0 g}{1 mol}$ = 19.0 g S
c. Mass of 2.78 mol $CH_{2}Cl_{2}$
Molar mass of $CH_{2}Cl_{2}$ = 1 x 12.0 + 2 x 1.00 + 2 x 35.45
Molar mass of $CH_{2}Cl_{2}$ = 49.45 g
2.78 mol $CH_{2}Cl_{2}$ x $\frac{49.45 g}{1 mol}$ = 236.02 g
So the mass of 2.78 mol $CH_{2}Cl_{2}$ is 236 g ( to three significant figures).
d. Mass of 38 mol ${(NH_{4}})_2S$
Molar mass of ${(NH_{4}})_2S$ = 2 x 14.00 + 8 x 1.00 + 32.06
Molar mass of ${(NH_{4}})_2S$= 68.06 g
38 mol ${(NH_{4}})_2S$ x $\frac{68.06 g}{1 mol}$ = 2,586.3 g
So the mass of 38 mol ${(NH_{4}})_2S$ is 2.59 x$10^{3}$ g ( to three significant figures)
