## Chemistry (7th Edition)

Avogrado's number is equal to $6.02 \times 10^{23}$.
Each $HCl$ molecule has 36.5 u, so we can use the convertions given to calculate the number of molecules in 1 mol: $\frac{1molecule}{36.5u} \times \frac{1u}{1.6605 \times 10^{-24}g} \times \frac{36.5g}{1mol} = 6.02 \times 10^{23}molecules/mol$. Avogrado's number is exactly the number of molecules in 1 mole. In this case, since we've used the molar mass and weight for the molecule, it is the number of molecules in 1 mole.