posted by Anonymous .
Hi, I was wondering if someone could clear this up for me. Anodes and cathodes. Which is which?
I'm getting mixed information from different textbooks, review books, and websites and I'm confused.
My review book states that The cathode is negative and the anode is positive, but other resources tell me otherwise. The review book also has a diagram showing cathode rays (-) flowing in the direction of the anode (+). But online it says the direction of flow is always from the anode to cathode. Is that just the case outside the device?
This is a confusing point and most text books get it right; however, they often fail to CLEARLY define which system they are discussing. Here is the correct skinny.
By definition, the anode is where oxidation occurs. That is the ONLY definition that counts. It is the ONLY one that is correct in all situations.
Having said all of that,
a) in batteries, the anode is the negative electrode.
b) in electrolysis cells (electroplating), the anode is the positive electrode.
In my classes, it is/was usual that students coming in to college chemistry thought that the anode was positive and the cathode was negative. In fact, I was taught that in grade school and high school. The fact is we were ALWAYS talking about electrolytic cells. In college the prof starts talking about the anode (and it was clearly marked negative) and I came unglued.
Ah, that makes a bit more sense. Thanks for clearing it up for me.