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?
If I have 6 chocolates, and give 4 away, how many chocolates do I have left?
Now of course you wanted the number of atoms remaining in the balloon. But the use of a
One mole of stuff specifies
So, I am left with