Answer
a. Mass of 0.331 mol Fe is 18.5 g (to three significant figures).
b. Mass of 2.1 mol F is 39.9 g
c. Mass of 0.034 mol $CO_{2}$ is 1.50 g
d. Mass of 1.89 mol $K_{2}CrO_{4}$ is 367 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 0.331 mol Fe. Molar mass of Fe is 55.84 g/mol. Therefore :
0.331 mol Fex $\frac{55.84 g Fe}{ 1 mol Fe}$ = 18.48 g Fe
Mass of 0.331 mol Fe is 18.5 g (to three significant figures).
b. Mass of 2.1 mol F.
Molar mass F 18.99 g/mol, therefore:
2.1 mol F x $\frac{18.99 g}{1 mol}$ = 39.88 g
Mass of 2.1 mol F is 39.9 g (to three significant figures)
c. 0.034 mol $CO_{2}$
Molar mass $CO_{2}$ = 1 x 12.01 + 2 x 15.99
Molar mass $CO_{2}$ = 43.99 g/mol
0.034 mol $CO_{2}$ x $\frac{43.99 g}{1 mol}$ =1.50 g (to three significant figures) .
d. Mass of 1.89 mol $K_{2}CrO_{4}$
Molar mass $K_{2}CrO_{4}$ = 2 x 39.09 + 1 x 51.99 +4 x 15.99
Molar mass $K_{2}CrO_{4}$ = 194 g/mol
1.89 mol $K_{2}CrO_{4}$ x $\frac{194g}{1 mol}$ = 366.9 g
The mass of 1.89 mol $K_{2}CrO_{4}$ is 367 g ( to three significant figures)
