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

Scientific notation is the standardized way to represent any number as the product of a real number and a power of ten. Apply Avogadro's constant which is 6.023x10^23 molecules per mole.

20x10^22 molecules / 6.023x10^23 molecules per mole = 0.33 moles.