# How many helium atoms are in a helium blimp containing 494 kg of helium?

Jul 23, 2016

$7.44 \cdot {10}^{28}$ atoms

#### Explanation:

Step 1: calculate how the number of moles using the molar mass.
The molar mass of helium = $4.00$ g/mol.
This means that 1 mole of helium atoms weighs 4 gram.

In this case you have $494$ kg which is $494.000$ grams. How many moles is this?

$\frac{494.000 \textcolor{red}{\cancel{\textcolor{b l a c k}{g r a m}}}}{4.00 \frac{\textcolor{red}{\cancel{\textcolor{b l a c k}{g r a m}}}}{m o l}} = 123.500 m o l$

Step 2 : calculate the number of atoms using Avogadro's constant.
Avogadro's constant states that there are $6.02 \cdot {10}^{23}$ atoms in one mole of any element.

How many atoms are in 123.500 moles?

$6.02 \cdot {10}^{23} \text{atoms"/color(red)cancel(color(black)((mol))) * 123.500 color(red)cancel(color(black)(mol)) = 7.44*10^28 "atoms}$