# What mass of anhydrous salt is required to prepare a 50*g mass of "acetic acid trihydrate", H_3C-CO_2H*3H_2O?

May 5, 2017

You want approx. $30 \cdot g$ of the anhydrous salt.

#### Explanation:

Sodium acetate trihydrate has a formula mass of $136.04 \cdot g \cdot m o {l}^{-} 1$.

And thus a $50 \cdot g$ mass is a molar quantity of..........

$\frac{50 \cdot \cancel{g}}{136.04 \cdot \cancel{g} \cdot m o {l}^{-} 1} = 0.368 \cdot \frac{1}{\frac{1}{m o l}} = 0.368 \cdot m o l .$

Now this is $0.368 \cdot m o l$ with respect to sodium and acetate ions, but $1.10 \cdot m o l$ with respect to water.

And so we use the given molar quantity to calculate an equivalent mass of the ANHYDROUS salt:

$0.368 \cdot \cancel{m o l} \times 82.03 \cdot g \cdot \cancel{m o {l}^{-} 1} = 30.2 \cdot g$