Question

Write the formula of the following compounds:
(i) Potassium trioxalatoaluminate (III)
(ii) Hexaaquairon(II) sulphate.

Answer 1

The formula of the compounds is given below.
(i) Potassium trioxalatoaluminate (III)
$K_3\left[Al\right(C_2{O}_4{)}_3]$
Oxalate ion has $-2$ charge. 3 oxalate ions have $-2\times 3=-6$ charge which is balanced with $+3$ charge on one Al ion and $+3$ charge on 3 K ions (each K ion has $+1$ charge).
(ii) Hexaaquairon(II) sulphate.
$\left[Fe\right(H_{2}O{)}_6]S{O}_4$
It has 6 water ligands. The $-2$ charge on sulphate ions is balanced with +2 charge on ferrous ion.