Concept:A coordination compound is neutral, so the charges of its complex ion and counter-ions must balance.
Explanation:"Hexacyanoferrate(II)" indicates six cyanide ions,
CN−, coordinated to one iron(II) ion.
Iron(II) has a charge of
+2, and six
CN− ions give a total charge of
−6.
Therefore, the complex ion is
[Fe(CN)6]4−, because
+2+(−6)=−4.
Potassium,
K+, balances this negative charge.
Four
K+ ions are required:
4(+1)+(−4)=0.
So the correct formula is
K4Fe(CN)6.
Answer:D.
K4Fe(CN)6