Answer:
3.25 x 10²⁴ molecules H₂O
Explanation:
To find the number of H₂O molecules, you need to (1) convert grams to moles (via molar mass) and then (2) convert moles to molecules (via Avogadro's Number). It is important to arrange the ratios/conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the amount of sig figs in the given value.
Atomic Mass (H): 1.008 g/mol
Atomic Mass (O): 16.00 g/mol
Molar Mass (H₂O): 2(1.008 g/mol) + 16.00 g/mol
Molar Mass (H₂O): 18.016 g/mol
Avogadro's Number:
6.02 x 10²³ molecules = 1 mole
97.2 g H₂O 1 mole 6.02 x 10²³ molecules
------------------ x ------------------- x ------------------------------------ =
18.016 g 1 mole
= 3.25 x 10²⁴ molecules H₂O
