So CN- is just a Lewis Base and not an Oxidizing agent?

[johnwandering]

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4Au + 8CN(-) + O2 + H2O -----> 4Au(CN)2 (-) + 4OH-

What is the role of CN- in the first reaction in the purification of gold?
a.) Reducing agent
b.) Oxidizing agent
c.) Lewis Acid
d.) Lewis Base


In terms of "need to know specific information" this seems to be the most difficult question I ever came across.

Au changes oxidation states from 0 to +1 in this reaction. Yet CN- is NOT considered an oxidizing agent. In fact, it is just classified as a "Lewis Base" that just clings onto Au.


This is fairly startling for me because there is no mention in the passage or the equation that would lead me to make this conclusion. I was wondering how to correctly solve these problems in the future and recognize Lewis Acids/Base opposed to oxidizing/reducing agents.

 

[chaser0]

I believe you have to consider that the oxidizing reagent has to be reduced.

It seems that CN- becomes oxidized if anything, eliminating from consideration as an oxidizing reagent.

 

[MedPR]

4Au + 8CN(-) + O2 + H2O -----> 4Au(CN)2 (-) + 4OH-

What is the role of CN- in the first reaction in the purification of gold?
a.) Reducing agent
b.) Oxidizing agent
c.) Lewis Acid
d.) Lewis Base


In terms of "need to know specific information" this seems to be the most difficult question I ever came across.

Au changes oxidation states from 0 to +1 in this reaction. Yet CN- is NOT considered an oxidizing agent. In fact, it is just classified as a "Lewis Base" that just clings onto Au.


This is fairly startling for me because there is no mention in the passage or the equation that would lead me to make this conclusion. I was wondering how to correctly solve these problems in the future and recognize Lewis Acids/Base opposed to oxidizing/reducing agents.

CN- is never reduced, so it cannot be an oxidizing agent. Au oxidation state goes from 0 to +1 so it is oxidized, making it the reducing agent and O2 oxidation state goes from 0 to -2 so it is reduced, making it the oxidizing agent.