Salt Bridges/anodes/cathodes-with my answers

Question

A standard galvanic cell is constructed with Cd2+|Cd and F2|F- half cell compartments connected by a salt bridge. Which of the following statements are correct?
Choose all that apply:

A. As the cell runs, anions will migrate from the Cd2+|Cd compartment to the F2|F- compartment.
B. In the external circuit, electrons flow from the Cd2+|Cd compartment to the F2|F- compartment.
C. The anode compartment is the F2|F- compartment.
D. The anode compartment is the Cd2+|Cd compartment
E. Cd2+ is reduced at the cathode

I keep getting this problem wrong and do not understand why. I think A and D are correct.

Answer 1

Hello Sam,

I made you a video on our YouTube channel about Galvanic Cells: https://www.youtube.com/watch?v=W_G6Go6VVOA

 

Feel free to ask any additional homework problems to be reviewed at http://www.drawntochemistry.com.

Hope this helps a bit! 

Answer 2

Well, Sam, this is a nice extreme case, so it has a direct analysis. The F₂ is obviously being reduced to F⁻, which means the Cd is oxidized to Cd²⁺.

 

Using the tacky but easy to remember mnemonic device "red cat, an ox" the Cd is the anode, while the F₂ is the cathode material.

 

The electrons leave the anode along the external circuit, so a negative charge must migrate in to balance this.

 

So, your choice of A is incorrect, as the anions need to migrate into that compartment.

Electrons flow from the anode, which makes B a correct choice.

F₂ is reduced, which happens in the cathode, so C is incorrect.

D is correct - the Cd is oxidized, which is the anode reaction.

E is the wrong reaction, so it is incorrect.