Question

Calculate the number of moles and molecules and atoms present in 0.8mg of helium gas

Answer 1

Hey buddy! Here's your answer!

0.8 mg = 8 x 10^-4 g

4 gram              ===> 1 mole

8 x 10^-4 gram ===> ?

? = 8 x 10^-4 gram x 1 mole/4 gram

? = 4 x 10^-4

He = 0.0004 mole

4 gram              ===> 6 x 10^23 molecules

8 x 10^-4 gram ===> ?

? = 8 x 10^-4 gram x 6 x 10^23 molecules/4 gram

He = 24 x 10^-19 molecules

Hope this helps! :)