Moles and Molar Mass Practice Test

A sample of pure aluminum, $\mathrm{Al}$, contains $3.01\times 10^{23}$ atoms. How many moles of $\mathrm{Al}$ are in the sample? (Avogadro's number: $6.022\times 10^{23}\ \mathrm{mol^{-1}}$.)

A sample of pure potassium bromide, $\mathrm{KBr}$, has a mass of $11.9\ \mathrm{g}$. (Atomic masses: $\mathrm{K}=39.1$, $\mathrm{Br}=79.9$.) How many moles of $\mathrm{KBr}$ are in the sample?