Question

question 1 3 pts
how many molecules of so₃ are in 4.85 x 10⁻² g of so₃? the molar mass of so₃ is 80.06 g/mol.
○ 6.34 x 10³⁴ molecules
○ 1.59 x 10²⁶ molecules
○ 3.65 x 10²⁰ molecules
○ 2.71 x 10⁶ molecules
○ 8.03 x 10¹⁵ molecules

Explanation:

Step1: Calculate moles of SO₃

Use the formula $n=\frac{m}{M}$, where $m$ is mass and $M$ is molar - mass. Given $m = 4.85\times10^{-2}\text{ g}$ and $M = 80.06\text{ g/mol}$.
$n=\frac{4.85\times 10^{-2}\text{ g}}{80.06\text{ g/mol}}\approx6.06\times10^{-4}\text{ mol}$

Step2: Calculate number of molecules

Use Avogadro's number $N_A = 6.022\times10^{23}\text{ molecules/mol}$. Multiply the number of moles by Avogadro's number: $N=n\times N_A$.
$N=(6.06\times 10^{-4}\text{ mol})\times(6.022\times10^{23}\text{ molecules/mol})\approx3.65\times10^{20}\text{ molecules}$

Answer:

$3.65\times 10^{20}$ molecules