# Question 65e0b

${K}_{2} \left[F e {\left(C \equiv N\right)}_{6}\right]$, $\text{potassium ferrocyanide}$, ${K}_{3} \left[F e {\left(C \equiv N\right)}_{6}\right]$, $\text{potassium ferricyanide}$, are the typical $\stackrel{+ I I I}{\text{Fe}}$ and $\stackrel{+ I I}{\text{Fe}}$ salts. How to assign these numbers? Look at the formulae of the salts, we got 3xxK^+ +Fe^(3+) + 6xx""^(-):C-=N, to give a NEUTRAL ferric salt; else 2xxK^+ +Fe^(2+) + 6xx""^(-):C-=N# to give the ferrous salt.