Answer
a. 0.9393 mol of $Fe_2O_3$
b. $2.17 \times 10^{-4}$ mol of $NO_2$
c. $2.5 \times 10^{-8}$ mol of $BF_3$
Work Step by Step
a. - Calculate or find the molar mass for $ Fe_2O_3 $:
$ Fe_2O_3 $ : ( 55.85 $\times$ 2 )+ ( 16.00 $\times$ 3 )= 159.7 g/mol
- Using the molar mass as a conversion factor, find the amount in moles:
$$ 150.0 \space g \times \frac{1 \space mole}{ 159.7 \space g} = 0.9393 \space mole$$
b.- Calculate or find the molar mass for $ NO_2 $:
$ NO_2 $ : ( 14.01 $\times$ 1 )+ ( 16.00 $\times$ 2 )= 46.01 g/mol
- Using the molar mass as a conversion factor, find the amount in moles:
$$ 10.0 \space mg \times \frac{1 \space g}{1000 \space mg} \times \frac{1 \space mole}{ 46.01 \space g} = 2.17 \times 10^{-4} \space mole$$
c.- Use avogadro's number as a conversion factor to find the amount of moles:
$$ 1.5 \times 10^{16} \space BF_3 \times \frac{1 \space mol}{6.02 \times 10^{23} \space BF_3 } = 2.5 \times 10^{-8} \space mol \space BF_3 $$
