Answer:
3 significant figures.
Explanation:
So, a mole is essentially a group of things. In this case, a mole of carbon dioxide will contain
6.022 ⋅ 10 [ by the 23rd power]
molecules of carbon dioxide. In other words, in order to have
1 molecule of carbon dioxide, you need to have 6.022 ⋅ 10 [by the 23rd power] molecules of carbon dioxide.
You know that 5.00 ⋅ 10 [ by the 2nd power] molecules of carbon dioxide are exhaled from the lungs when we breathe out. You can use Avogadro's constant as a conversion factor to help you figure out how many molecules are present.