A standard galvanic cell is constructed in which a Cd2+ | Cd half cell acts as the cathode.

Question

(Choose all that apply.)
As the cell runs, anions will migrate from the other compartment to the Cd2+|Cd compartment.
The cathode reaction is Cd2+ + 2e- -> Cd.
Fe3+|Fe2+ could be the other standard half cell.
Cd is oxidized at the cathode.
In the external circuit, electrons flow from the other compartment to the Cd2+|Cd compartment.

Answer 1

Chastity,

 

The key to getting started with this problem is to remember that reduction takes place at the cathode. The next thing to realize is that you don't have to answer the question in the order given. I would suggest starting with the easiest of the five options and that would be that second one - "The cathode reaction is Cd2+ + 2e- –> Cd." If you have already started with the key idea - reduction takes place at the cathode - then it is clear that this equation should be correct since it shows Cd2+ being reduced. At this point you can go back and evaluate the first option - "As the cell runs, anions will migrate from the other compartment to the Cd2+|Cd compartment." From the cathode reaction equation you can see that the solution will become less positive (or more negative) since cations, Cd2+, are being removed from solution. Since the solution is becoming more negative we would not expect negative ions to move into the solutions from the other compartment. In fact we would expect the opposite of this - cations moving into the cathode compartment. Continue to analyze the other options in a similar manner.

 

Please keep in mind that I am available for online tutoring.

 

Thanks

 

Thomas

Answer 2

Hello Chastity,

 

As promised, I made you a video on our YouTube channel: https://www.youtube.com/watch?v=W_G6Go6VVOA

 

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

 

Once you've reviewed the basics, read this: 

1."As the cell runs, anions will migrate from the other compartment to the Cd2+|Cd compartment." So electrons are not the same as anions.

 

When referring to anions, they are speaking of the elements used in the reaction. Anions move towards to anode using the salt bridge, just as cations migrate towards the cathode using the salt bridge.

 

A wire is too small to transport complete elements, thus acting as a good conductor of only electrons.

 

This process is what allows a cell to continue reacting and not "use up" all of the available redox reactions.

 

2. "The cathode reaction is Cd2+ + 2e- -> Cd".

 

This is a reduction reaction as the positive charge is being reduced by gaining electrons. Therefore, yes this reaction occurs at the cathode because the RED CAT ate AN OX. Reduction occurs at the cathode, oxidation occurs at the anode.

 

 
3. "Fe3+|Fe2+ could be the other standard half cell".

 

This is also a reduction reaction, therefore, this would occur at the cathode and not make up the other standard half. We need an oxidation reaction to act at the anode. 

 

4. "Cd is oxidized at the cathode"

 

Cd is being reduced in this example. Oxidation reactions occur at the anode and reduction reactions occur at the cathode (a RED CAT ate AN OX).

 

5. "In the external circuit, electrons flow from the other compartment to the Cd2+|Cd compartment."

 

Yes, electrons flow away from the negatively charged anode to the positively charged cathode.