Question

Potassium selenate is isomorphous with potassium sulphate and contains `50.0%` of `Se`. The atomic weight of `Se` is
a. `142`, b. `71`, c. `47.33`, d. `284`

Answer 1

a. `K_(2)SO_(4)` and Potassium selenate are isomorphous. So the formula is `K_(2)SeO_(4)`.
`Mw` of `K_(2)SeO_(4) = (39 xx 2 + x + 64)`
`= (142 + x)g`
`:. (142 + x)` of `K_(2)SeO_(4) implies x g` of `Se`
`100 g` of `K_(2)SeO_(4) = (x)/((142 +x)) xx 100`
`:. (x xx 100)/((142 + x)) = 50`
`Aw` of `Se = x = 142`