Redox reaction; standard cell potential

[lemin_rew]

Homework Statement

Find the cell potential of the equations
Mg^+2 + 2e- --------> mg E=-2.36v
Cl2 + e- ---------> 2cl- E=+1.36v

Ans: -1.00v

The Attempt at a Solution

The answer says that it cl2 should be flipped. And cl2 is the anode
But I don't understand why. I thought the -ve value sholud be flipped,
Also why is cl2 the anode, it's very high up on the SOA chart, which is cathode whereas mg is on the bottom. Is there any way to figure it which one is cathode and anode without the chart?
Is the more negative value always going to be flipped?
Can someone explain this.?

 

[nate808]

Hello,

Thank you for your post. To answer your question, it is important to understand the basics of electrochemistry and how to determine the cell potential of a redox reaction.

Firstly, the cell potential of a redox reaction is a measure of how much energy is released or absorbed during the reaction. It is a combination of the reduction potential of the cathode (where reduction occurs) and the oxidation potential of the anode (where oxidation occurs). The more positive the cell potential, the more favorable the reaction is.

In this case, we have two half-reactions: Mg^+2 + 2e- --------> Mg and Cl2 + 2e- --------> 2Cl-. The reduction potential of Mg (E = -2.36v) is more negative than the reduction potential of Cl2 (E = +1.36v). This means that Mg is more likely to undergo reduction than Cl2. Therefore, in order for the reaction to occur spontaneously, Cl2 must be the anode and Mg must be the cathode.

The reason for this is because in a redox reaction, electrons are transferred from the anode to the cathode. In other words, the anode is the site of oxidation (loss of electrons) and the cathode is the site of reduction (gain of electrons). The more negative reduction potential of Mg means that it is more likely to gain electrons, and therefore must be the cathode.

In terms of determining which is the anode and cathode without a chart, it is important to remember that the more negative reduction potential will always be the cathode and the more positive reduction potential will always be the anode. This is because the reaction with the more negative reduction potential will be favored, and therefore will occur at the cathode.

I hope this explanation helps to clarify why Cl2 must be the anode and why the more negative value is flipped. If you have any further questions, please let me know. Keep up the good work in your studies!