Answer
a. $180.157\text{ grams}$
b. $2.78*10^{-3}\text{ mol}$
$1.67*10^{21}\text{ molecules}$
Work Step by Step
a. $\text{ Molar Mass}=9*12.0107+8*1.00794+4*15.9994=180.157\text{ grams}$
b. $0.500\text{ grams}*\frac{1\text{ mol}}{180.157\text{ grams}}=2.78*10^{-3}\text{ mol}$
$0.500\text{ grams}*\frac{1\text{ mol}}{180.157\text{ grams}}*\frac{6.0221*10^{23}\text{ molecules}}{1\text{ mol}}=1.67*10^{21}\text{ molecules}$
