# How would you know when you had a mole of a substance for which you knew the formula?

Mar 26, 2018

You determine the molar mass (mass of one mole) of the substance. Then obtain that mass using a laboratory balance, and you will have one mole of the substance.

#### Explanation:

Example:

Obtain one mole of calcium chloride $\left(\text{CaCl"_2}\right)$.

Determine the molar mass of $\text{CaCl"_2}$ by multiplying the subscript of each element by its molar mass (atomic weight on the periodic table in g/mol).

Molar mass $\text{CaCl"_2} :$

(1xx"40.078 g/mol Ca") + (2xx"35.453 g/mol Cl")="110.984 g/mol"

Use a balance to mass out $\text{110.984 g CaCl"_2}$. This is one mole of calcium chloride.