# Calculate the weight proportion of H2O in Na2S2O2.5H2O?

Oct 21, 2017

Are you sure you don't mean $\text{sodium thiosulfate pentahydrate}$, i.e. $N {a}_{2} {S}_{2} {O}_{3}$? I make $\text{percentage water}$ approx. 60%.

#### Explanation:

We can calculate the percentage of water BY mass in $N {a}_{2} {S}_{2} {O}_{3} \cdot 5 {H}_{2} O$....

i.e. ="Mass of water"/"Mass of hydrate"=(5xx18.01*g*mol^-1)/(158.11 *g*mol^-1)xx100%

=??%

Just in regard to ${S}_{2} {O}_{3}^{2 -}$, I have always liked to imagine this as $S {O}_{4}^{2 -}$ where ONE of the oxides has been replaced by sulfide ion, the which assumes the SAME oxidation number as oxide, and thus we gots $S \left(V I +\right)$ and $S \left(- I I\right)$, an AVERAGE oxidation state of $S \left(+ I I\right)$.