Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: toshin on October 08, 2012, 10:24:53 PM
-
Hello this is my first post, hopefully I'll do it right,
I've some questions about electrochemistry that neither my teachers or google could help me.
I kind of found something in here but I'm still a bit confused.
First of all, I still can't get what does drive the reaction in a galvanic cell, are the electrodes already charged just because they are in contact with their respective solution, commonly Zn(s) + ZnSO4(aq) and Cu(s) + CuSO4(aq) or they only get charged when the circuit is closed ? In other words, does the reaction ignite with the oxidation of the zinc or because the copper "forces" the zinc to give him electron by oxidizing.
Then I red a lot of different explanations about the factors which defines the EMF of an element.
The value, I know that it comes from the experiment with an hydrogen cell, but, why is copper stronger than zinc and what determines that ?
Hope I was clear enough,
Thanks for your help
-
Yes, it is enough to put the electrode in the solution to get it slightly charged.
-
Thanks for replying.
But then, the copper electrode get slightly charged too no ?
-
Both electrodes get charged. If the circuit is closed then the reaction takes place.
-
The fact that Cu2+ is reduced and zinc is oxidized is due to basic properties of the materials. You can think of it as zinc "likes" to give up electrons more than copper does, and copper is "happier" in a zero oxidation state than zinc is. These properties manifest themselves in the standard reduction potentials for each of these half-reactions. For some materials, you can infer which likes to be oxidized more. For instance, lithium is extremely electropositive and fluorine is extremely electronegative, so Li will be oxidized easily and fluorine wont. However, when it comes to metals like Zn and Cu it is best just to memorize or use a table.