JEE Main levelSingle correct optionDifficulty 2 of 3si184
Prussian blue, formed in the Lassaigne test for nitrogen, has the formula FeX4[Fe(CN)X6]X3. The total number of cyanide ligands in one formula unit is
A18
B6
C12
D24
Answer: A
Each complex ion [Fe(CN)X6]X4− has 6 cyanide ligands and there are 3 such ions in the formula unit, so the total is 3×6=18.