help with questions

[bturville]

Basically to draw it you just need to work out a bunch of things, and then put them all together into a diagram. For electrolytic cells:

Cathode is negative, and where reduction occurs. Anode is positive, and where oxidation occurs. The copper is plated at the cathode, but you also need copper at the anode as a source of Cu2+ ions.

Get used to drawing these, they love to ask them. Your diagram looks ok. You showed the polarity of the electrodes with the + and -, which is all good. Also make sure you know the difference between electrochemical and electrolytic cells, with regard to flow direction, electrode polarity, etc etc. tis important.

[Rosie]

where does the direction of electrons flow, to the cathode or the anode along the wires?

[polky]

where does the direction of electrons flow, to the cathode or the anode along the wires?

In an electrolytic cell, the electrons flow to the cathode (negative polarity) electrode.

[Rosie]

thanks for that!

Now, I'm not quite sure what the anode and cathode reactions are for a silver electroplating cell using AgNO₃ electrolyte.

[Collin Li]

In all cells (galvanic and electrolytic), the electron flow is anode to cathode. Think about what happens at the anode... oxidation, a loss of electrons. Hence, electrons are leaving the anode and being 'gained' at the cathode always.

[Rosie]

thanks for that!

Now, I'm not quite sure what the anode and cathode reactions are for a silver electroplating cell using AgNO₃ electrolyte.

I'm pretty sure that you would just use the half equation of silver for the anode and cathode reactions, yet just reversed as nitrate isnt in the electrochemical series. is this right

[Collin Li]

Yes, this is right. Your net reaction is zero, but your anode and cathode reactions are just the reverse of each other (at the anode, solid silver becomes silver ions, and at the cathode, silver ions become solid silver).

[Rosie]

What about the cathode and anode half reactions of a chromium electroplating cell using Cr(NO₃)₃ electrolyte.

Is the half equation this: Cr₂O₇^2- + 14H⁺ + 6e- ----> 2Cr³⁺ + 7H₂O

[Collin Li]

Nope.

cathode:

anode:

Net reaction: zero (usually the case for electroplating)

[Rosie]

Ok thanks.

And for the anode and cathode reactions for a tin electroplating cell using Sn(NO₃)₂ electrolyte.


Is the half equation :Sn⁴⁺ + 2e-  -----> Sn²⁺ or Sn²⁺ + 2e- ----> Sn

thanks

[Collin Li]

Because tin (II) nitrate has tin in an oxidation state of +2, it is the 2nd one.

[Rosie]

thank you so much.

Question...
As the reactions proceed, what happens to the concentration of the metal ions in the solution in each cell?

[polky]

thank you so much.

Question...
As the reactions proceed, what happens to the concentration of the metal ions in the solution in each cell?

The concentration of the metal ions would not change, because as the cations are being produced by oxidation at the anode, the cations are consumed at the cathode, being reduced to produce the solid metal (thus plating).

[Rosie]

thanks for that

another....
What is the relationship between the mass deposited and the charge for a particular cell?

[Collin Li]

An inverse relationship:

Larger charge means that more electrons are required. For a given amount of electrons (charge), there is a smaller mass deposited for higher charges.