Consider the coordination compound potassium trioxalatoferrate(III). Let be the primary valency (oxi — Coordination Compounds Chemistry Question
Question
Consider the coordination compound potassium trioxalatoferrate(III). Let $x$ be the primary valency (oxidation state) of iron, $y$ be its secondary valency (coordination number), and $z$ be the total number of potassium atoms in one formula unit. Find the value of $(x^2 + y^2) / z$.
💡 Solution & Explanation
The name is potassium trioxalatoferrate(III). The oxidation state of iron is explicitly given as $+3$, so $x = 3$. There are three oxalato ligands ($C_2O_4^{2-}$), which are bidentate. Therefore, the secondary valency (coordination number) is $3 \times 2 = 6$, so $y = 6$. The complex sphere is $[Fe(C_2O_4)_3]^{3-}$, as $Fe$ is $+3$ and $3$ oxalates contribute $-6$. To balance the $-3$ charge, $3$ potassium ions are required ($K_3[Fe(C_2O_4)_3]$), so $z = 3$. Calculating the expression: $(3^2 + 6^2) / 3 = (9 + 36) / 3 = 45 / 3 = 15$.