# How many moles of KCl are in 27.5 g of KCl?

Oct 28, 2015

0.369 moles

#### Explanation:

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, $K$ = $39.10 \frac{g}{\text{mol}}$

atomic weight of chlorine, $C l$ = $35.45 \frac{g}{\text{mol}}$

Afterwards, you need to get the sum of the atomic weights. For the problem above,

molar mass of $K C l$ = $74.55 \frac{g}{\text{mol}}$

Now, we are ready to convert.

$27.5 \cancel{\text{grams KCl}}$ x $1 \text{mol KCl"/(74.55 cancel "grams" KCl) = 0.369 "mol KCl}$