# How many molecules are in 3 moles of H_2S?

Jun 27, 2016

$1.8 \cdot {10}^{24} \text{molecules}$

#### Explanation:

As you know, a mole is simply a very, very large collection of molecules.

In order to have one mole of a molecular substance, you need to have $6.022 \cdot {10}^{23}$ molecules of that substance $\to$ this is known as Avogadro's number and it can be used as a conversion factor to go from number of molecules to moles and vice versa.

$\textcolor{b l u e}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} \text{1 mole" = 6.022 * 10^(23)"molecules} \textcolor{w h i t e}{\frac{a}{a}} |}}}$

Now, you want to know how many molecules are present in $3$ moles of hydrogen sulfide, $\text{H"_2"S}$.

According to Avogadro's number, $1$ mole of hydrogen sulfide contains $6.022 \cdot {10}^{23}$ molecules of hydrogen sulfide, which means that $2$ moles will contain

3 color(red)(cancel(color(black)("moles H"_2"S"))) * overbrace((6.022 * 10^(23)"molecules H"_2"S")/(1color(red)(cancel(color(black)("mole H"_2"S")))))^(color(blue)("Avogadro's number")) = color(green)(|bar(ul(color(white)(a/a)color(black)(1.8 * 10^(24)"molecules H"_2"S")color(white)(a/a)|)))

I'll leave the answer rounded to two sig figs.