A sample of $\mathrm{CO}_{2}$ has a mass of 50.0 grams. What is number of molecules of carbon dioxide in the sample? ( $\mathrm{C}=12.0 \mathrm{u}, \mathrm{O}=16.0 \mathrm{u}$, and $1 \mathrm{u}=1.66 \times 10^{-27} \mathrm{~kg}$.)
A) $6.85 \times 10^{23}$
B) $4.95 \times 1023$
C) $5.66 \times 1023$
D) $4.02 \times 1023$
E) $6.02 \times 10^{23}$

Question

Quizplus · Accepted Answer

First, calculate the molar mass of CO2: $12.0 \, \text{g/mol} + 2 \times 16.0 \, \text{g/mol} = 44.0 \, \text{g/mol}$. Then, use the formula $n = \frac{m}{M}$ to find moles of CO2: $n = \frac{50.0 \, \text{g}}{44.0 \, \text{g/mol}} \approx 1.136 \, \text{mol}$. Finally, use Avogadro's number ($6.022 \times 10^{23} \, \text{mol}^{-1}$) to find the number of molecules: $1.136 \, \text{mol} \times 6.022 \times 10^{23} \, \text{mol}^{-1} \approx 6.85 \times 10^{23}$.

A Sample Of CO2\mathrm{CO}_{2}CO2​ Has a Mass of 50 C=12.0u,O=16.0u\mathrm{C}=12.0 \mathrm{u}, \mathrm{O}=16.0 \mathrm{u}C=12.0u,O=16.0u

A Sample Of $\mathrm{CO}_{2}$ Has a Mass of 50 $\mathrm{C}=12.0 \mathrm{u}, \mathrm{O}=16.0 \mathrm{u}$