Chemistry Forum

I DON’T GET THIS!

If KCN is added to an aqueous FeCl₃ solution will ferricyanide complex form?

If KCN (potassium cyanide) is added to an aqueous FeCl₃ (ferric chloride) solution, ferricyanide complex (Fe(CN)₆)₃- is not expected to form.

The addition of KCN to an aqueous solution of FeCl₃ will cause the formation of a complex between Fe₃+ and cyanide ion (CN-) as follows:

Fe₃+ + CN- ⇌ Fe(CN)₆₃-

This complex is known as ferricyanide and has a characteristic red color. However, this complex formation requires the presence of ferrous ion (Fe₂+) in the solution, which acts as a reducing agent and reduces Fe₃+ to Fe₂+. In the absence of Fe₂+, ferricyanide complex formation is not expected to occur.

Therefore, if KCN is added to an aqueous FeCl₃ solution in the absence of Fe₂+, ferricyanide complex is not expected to form.

However, this complex formation requires the presence of ferrous ion (Fe₂+) in the solution, which acts as a reducing agent and reduces Fe₃+ to Fe₂+. In the absence of Fe₂+, ferricyanide complex formation is not expected to occur

How should this work, how can Fe 2+ reduce Fe 3+

Where do you read it, that Fe 2+ is necessary.