Question

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

Answer 1

`7.44*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?

`(494.000 color(red)cancel(color(black)(gram)))/ (4.00 color(red)cancel(color(black)(gram))/(mol)) = 123.500 mol`

Step 2 : calculate the number of atoms using Avogadro's constant.
Avogadro's constant states that there are `6.02*10^23` atoms in one mole of any element.

How many atoms are in 123.500 moles?

`6.02*10^23 "atoms"/color(red)cancel(color(black)((mol))) * 123.500 color(red)cancel(color(black)(mol)) = 7.44*10^28 "atoms"`