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`

Options

A. Oxidation state of Se in the given compound is `+6`
B. Atomic weight of Se is `118.6`
C. Equivalent weight of potassium selenate is `130.3`
D. All the above

Answer

D

Explanation

Potassium selenate is isomorphous to `K_(2)SO_(4)` and thus its molecular formula is `K_(2)SeO_(4)`.
Now molecular weight of `K_(2)SeO_(4)`
`= (39 xx 2 +a +4 xx 16) = (142 +a)`
where a is atomic weight of Se
`(142 +a)g K_(2)SeO_(4)` has `Se = ag`
`100g K_(2)SeO_(4)` has `Se = (a xx 100)/(142 +a)`
`:. %` of `Se = 45.52`
`= 45.52 a = 118.6`
Also equivalents of `K_(2)SeO_(4) =`
`("Mol.wt")/(2) = (2 xx 39 +118.6 +64)/(2) = 130.1`