How many molecules are in 10.32 moles of H2O?

What the question is asking

You are converting from moles of water to the actual count of water molecules. The bridge between these is Avogadro’s number, which tells you how many molecules are in 1 mole.

Use Avogadro’s number

Avogadro’s number is $$N_A = 6.022\times 10^{23}\,\text{molecules/mol}.$$ Multiply the given moles by $N_A$: $$\text{molecules} = 10.32\times 6.022\times 10^{23}.$$

Calculate and write in scientific notation

First multiply the decimals: $$10.32\times 6.022 = 62.14704.$$ Now attach the power of ten: $$62.14704\times 10^{23} = 6.214704\times 10^{24}.$$ Rounding to 4 significant figures gives: $$6.215\times 10^{24}\text{ molecules of }H_2O.$$