# How do we find the formula mass of "chromic sulfite", Cr_2(SO_3)_3?

##### 1 Answer
Feb 17, 2017

$\text{Of chromic sulfite................?}$

#### Explanation:

We add the atomic masses of the the given constituents......of $C {r}_{2} {\left(S {O}_{3}\right)}_{3}$:

$= \left[2 \times 52.00 \left(C r\right) + 3 \times 32.06 \left(S\right) + 9 \times 16.00 \left(O\right)\right] \cdot g \cdot m o {l}^{-} 1$

$= 344.18 \cdot g \cdot m o {l}^{-} 1$.

All I have done is to take the atomic masses from the Periodic Table, and added them together appropriately. You are not expected to remember any of the atomic masses (tho' a few will stick).

What is the molar mass of $C {r}_{2} {\left(S {O}_{4}\right)}_{3} \cdot 18 {H}_{2} O$?