How many moles of KCl are in 27.5 g of KCl?
To convert a known weight of any substance into its number of moles, you need first to compute the molar (or molecular) mass of that substance.
In order to get the molar mass, you would need the atomic weights of the elements making up that substance (just consult a periodic table). In this case,
atomic weight of potassium,
atomic weight of chlorine,
Afterwards, you need to get the sum of the atomic weights. For the problem above,
molar mass of
Now, we are ready to convert.