Question

Aballoon contains 6.0 moles of helium. A hole in the balloon lets 4.0 moles of helium escape the balloon. How many atoms of m remain in the balloon?

Answer 1

If I have 6 chocolates, and give 4 away, how many chocolates do I have left?

Explanation:

Now of course you wanted the number of atoms remaining in the balloon. But the use of a `"mole"` specifies that number.

One mole of stuff specifies `6.022xx10^23` individual items of that stuff. To make things easier I could write `6.022xx10^23=N_A " Avogadro's number"`, which is something that would be recognized by all chemists (including you!).

So, I am left with `2xxN_A` helium atoms (of course helium is a mono-atomic gas). You can do the arithmetic if you like. Can you tell me the mass of gas left in the balloon?