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 H₂O) = (2.0 x 10²²) x 1 / 6.02 x 10²³

( Moles H₂O) = ( 2.0 x 10²² ) / 6.02 x 10²²

= 0.032 or 3.2 x 10⁻² molecules

hope this helps!