Question

How many moles of water, H2O, contain 2.0×1022 molecules of water? (See the hints for assistance in interpreting scientific notation.)

Express the quantity in moles to two significant figures.

Answer 1

1 mole ------------- 6.02 x 10²³ molecules
( moles ) ---------- 2.0 x 10²² molecules

moles = ( 2.0 x 10²² ) x 1 / 6.02 x 10²³

moles = 2.0 x 10²² / 6.02 x 10²³

= 0.03 moles of water

hope this helps!

Answer 2

2.0 x 10^22 molecules / 6.022 x 10^23 molecules mole
=0.332 mole so in significant figures 3.32*10^-1 moles of water, H2O, contain 2.0×1022 molecules of water