# What are "molality", and "molarity" of....?

## What are $\text{molality}$, and $\text{molarity}$ of a $30 \cdot g$ mass of $\text{ethylene glycol}$ in a $70 \cdot g$ mass of solvent?

Jul 13, 2017

We can find the $\text{molality}$ of $\text{ethylene glycol}$...............

#### Explanation:

$\text{Molality"="Moles of solute"/"Kilograms of solvent}$, whereas,

$\text{Molarity"="Moles of solute"/"Volume of solution}$.

Now given your specification we can define the $\text{molality}$ of $\text{ethylene glycol}$.....

$= \frac{\frac{30 \cdot g}{62.07 \cdot g \cdot m o {l}^{-} 1}}{70 \times {10}^{-} 3 \cdot k g} = 6.90 \cdot m o l \cdot k {g}^{-} 1$.....

But for $\text{molarity"="Moles of solute"/"Litres of solution}$, we have no handle on the volume of the solution.......because we don't know the solution density........... If, as likely, the solvent was water, the molarity would be equal to the molarity to a good first approx.