Electrochemistry - Galvanic/electrolytic cells prac (1 Viewer)

[gh0stface]

Hi, can anyone give me an outline of the two experiments relating to galvanic cells for electrochemistry topic (prod. of material).

• perform a first-hand investigation
to identify the conditions under
which a galvanic cell is produced

• perform a first-hand investigation
and gather first-hand information
to measure the difference in
potential of different
combinations of metals in an
electrolyte solution

Ive forgotten the stuff i did in the 1st prac, and was away for the second, someone please help me. A detailed outline of the 2nd prac would be greatly appreciated. Also wouldnt mind a copy of the pracs .


Thanks, greatly appreciate any help.

 

[177152]

The conditions are as follows...
Must be dissimilar(Different) metals or else no reaction will occur.

The metals must be immersed in an electrolytic solution and connected by a salt bridge (If metals are placed in solutions of their own ions) Mostly this point refers to a connection through solution being present but metals are separate.

Also an external circuit is required from the cathode to the anode to allow current flow (From Anode + to Cathode -), completing the circuit. (You know what I mean.)



As for the second prac, although it would be much better if I could attach a diagram..
The potential difference is increased as the difference in reactivity of the two metals increases (Ie. A highly reactive with a lowly reactive will produce the highest potential difference)

KNO3 is a common salt bridge chemical.

When two metals are touched together, the voltage drops off to zero.

When the metals are the same the voltage is zero

The electrons flow from the anode to the cathode through the EXTERNAL circuit. Ions flow through salt bridge from cathode to anode, I think.

The values obtained are less than the standard potential additions on the data sheet because of internal resistances, dirty or oxidised electrodes, and 'Polarisation' I think it's called, when the Hydrogen molecules are formed around one of the electrodes (Check for which one) it blankets the electrode reducing the surface area able to react.

I think that would be all you would need to know for that prac, I'm sorry it's not that clear, I hope it helped you a bit.. I'd have to go and get my prac book, but ask me what you don't know or whatever... It'll do me good to answer.

=)

 

[Undermyskin]

Um, pretty correct. The ions actually move in both direction: anions to anode and cations to cathode. However, it's not through if you are thinking that the anions from the cathode electrolyte and moving to the anode electrolyte. It's the ions in "saltbridge" solutions that migrate.

The metal strips are not necessarily immersed in the solution, half or just a bit is enough to create a high enough to measure electricity current. I'm quite sure that doesn't affect the potential sum or somethig much. Even if they are immersed totally, the value obtained is quite similar/ same.

Remember to choose the saltbridge solution which doesn't react with either electrolyte. As 177152 (your car insurance number or st?) said, KNO3 is the most common solution since all K and nitrates are soluble. You'd better revise the solubility table to avoid any silly mistakes. Most of my friends couldn't explain why KCl is a bad choice for Ag+ electrolyte. This is simply because AgCl is formed as precipitate!