Lab Report Electrochemistry

[catlover28]

does anyone have any ideas for an electrochemistry design lab??

[Keel]

does anyone have any ideas for an electrochemistry design lab??

Do you mean electrolysis an electolytic cell? What you can do is set up two voltic half-cells and measure the potential difference (how much electical energy is produced). Here's and image of what the cell looks like, you should have done something familiar in class:

Edited March 7, 2011 by Keel

[Sublime Sunshine]

An idea for something to investigate is perhaps the changes in potential difference with different half cells (reactants). Also, its important that you understand the difference between a voltaic cell and an electrolytic cell. Electrolysis happens in an electrolytic cell where you put in energy to fuel the reaction. This is a voltaic cell and is not electrolysis, it is a spontaneous reaction between two half cells.

[Drake Glau]

Keel, electrolysis=/=voltaic cells. Just to clarify if anyone reads your post weird.

You can set up a electrolytic cell for a lab as well though. You can test if increasing the current being inserted into the cell will increase the rate of electrolysis by measuring the mass of the cation attaching to the cathode

[dessskris]

Anybody has got any idea of a redox design experiment other than using voltaic cells, appropriate for Chem SL?

My teacher said redox experiments are usually using voltaic cells or electrolysis. We've done one using voltaic cells but it was just a practice (was not formally assessed). This Friday we are going to design another redox lab so I guess I am going to use electrolysis this time.

So what can I investigate using electrolysis? Any ideas would be highly appreciated

Edited March 7, 2011 by Desy ♫

[Sublime Sunshine]

Drake Glau raised the main experiment to do with electrolytic cells, to test if the amount of current changes the rate of electrolysis.

I spose you could also do things like vary temperature and pressure to see the impact upon the rate of electrolysis, but thats generally quite hard in a school lab. Another one you could try is see if different compounds have different rates of electrolysis... (you'd have to take molar ratios and charge etc in to account).

Well, that's it, I'm out of ideas

Are you sure you can't do something with a voltaic cell? There are quite a few different variables you could look at with that, even if it isn't the same variable as you tested last time.

[Keel]

So what can I investigate using electrolysis? Any ideas would be highly appreciated

You can set up a electrolytic cell for a lab as well though. You can test if increasing the current being inserted into the cell will increase the rate of electrolysis by measuring the mass of the cation attaching to the cathode

There are lots of other independent variables you can change:

-Changing the type of ions

-Changing the concentration of ions

-Changing current/voltage/resistance

-Type of electrode

Different dependent variables:

-Volume of gas produced

-Change in mass of electrode

[Drake Glau]

There is also the charges of the ions. It can easily affect the rate of electrolysis because something 2+ needs 2e- to attach to the cathode theoretically. You could test this pretty easily honestly by doing multiple cells using different salts like NaCl, BeCl2, and maybe some phosphate for a 3+ charged cation

[Center Field]

I feel like I got to this thread a little late.

But if you are gutsy and have time to do a little extra research, someone could do a design lab on electroplating.

You could set up a plating bath and measure the effects of numerous variables on the rate of deposition.

For example, kinetic theory predicts that the higher the temp, the higher the rate. Or you could even talk about how the charge value (what Drake meantions) affects the rate.

heh, I hope this was not generic.

[dessskris]

For example, kinetic theory predicts that the higher the temp, the higher the rate. Or you could even talk about how the charge value (what Drake meantions) affects the rate.

That one would fall under KINETICS then my design lab is on REDOX. So I don't want to investigate those kinetics stuffs like rate of reaction and temperature, mass, concentration, surface area, etc... We just designed a Kinetics lab last Friday and we're going to design a Redox lab this Friday

I am thinking of designing an experiment on electroplating but I am not too sure if I could because I guess it's only taught in HL? We have finished this chapter last month and I am pretty sure it's marked as AHL in the textbook anyway can I still do it? I actually studied it in IGCSE though so I roughly understand electroplating.

My rough ideas so far:

I want to copperplate a paperclip.

Electrolyte: a known volume and concentration of CuSO_{4 (aq)}

I am thinking of finding the Ar of copper. How?

First weigh the paperclip. Copperplate it. Reweigh the copperplated paperclip. The difference in mass is the mass of copper. Then to find Ar, divide that mass by the number of mol of Cu that you theoretically find.

However, for that to happen I need to make sure that the reaction finishes, right? How can I do that? Putting in a lot of paperclips until the last one uses the copper ions up? Isn't that stupid, though?

Do you think it's feasible or should I just leave that and investigate something else? I still have time to change it and get more ideas so if this experiment sounds stupid I will just think of something else. Any feedback would be highly appreciated!

[Keel]

Hey Desy,

It's alway good to keep your designs nice and simple. Always base it around the criteria, as long as you can formulate a foucused research question, state your variables clearly the complexity of the design doesn't matter, you won't be penalised for designing an experiment a six year old could come up with.

So what I'm trying to say is that you need to be more focused on what the examiner and moderators want to see and not on what you want to design. By making things complicated, you are risking the chance that you will get something wrong and providing the marker with an oppurtunity NOT to give you full marks. My teacher descibes IAs as jumping through hoops, it the simplest thing ever, just jump through the hoop and you get the marks, dont try to do a sumersault or a back-flip through the hoop because you are risking marks.

Back to your design, its doable but why dont you consider something simpler: a voltic cell experiment where your independent variables are the half cells and your dependent variable is the voltage produced? Or if you insist on electolysis why not vary the concentration in the electrolysis of AgNO3 and measure the volume of gas produced at the anode? There are lots of simpler experiments!

[Drake Glau]

For example, kinetic theory predicts that the higher the temp, the higher the rate. Or you could even talk about how the charge value (what Drake meantions) affects the rate.

That one would fall under KINETICS then my design lab is on REDOX. So I don't want to investigate those kinetics stuffs like rate of reaction and temperature, mass, concentration, surface area, etc... We just designed a Kinetics lab last Friday and we're going to design a Redox lab this Friday

I am thinking of designing an experiment on electroplating but I am not too sure if I could because I guess it's only taught in HL? We have finished this chapter last month and I am pretty sure it's marked as AHL in the textbook anyway can I still do it? I actually studied it in IGCSE though so I roughly understand electroplating.

My rough ideas so far:

I want to copperplate a paperclip.

Electrolyte: a known volume and concentration of CuSO_{4 (aq)}

I am thinking of finding the Ar of copper. How?

First weigh the paperclip. Copperplate it. Reweigh the copperplated paperclip. The difference in mass is the mass of copper. Then to find Ar, divide that mass by the number of mol of Cu that you theoretically find.

However, for that to happen I need to make sure that the reaction finishes, right? How can I do that? Putting in a lot of paperclips until the last one uses the copper ions up? Isn't that stupid, though?

Do you think it's feasible or should I just leave that and investigate something else? I still have time to change it and get more ideas so if this experiment sounds stupid I will just think of something else. Any feedback would be highly appreciated!

Desy, electroplating is just electrolysis. Yes, it's HL, but the concept is still SL honestly. The cation attaches to the cathode <-electroplating when it's metals

Don't worry about the completing reaction thing. Electrolysis rates are based off charges/current anyway. Make sure you have PLENTY of electrolyte and keep your time constant and this should be covered Really there is no...reaction...to complete. The electrolyte is dissociated in the solution and is simply attaching due to electrons and stuff, the completion of the "Reaction" is when the copper has completely covered the paperclip which would stop the reaction. Theoretically figuring this would be impossible as far as the IB chem goes (HL has nothing on this) because it would involved the surface area of the paperclip that's in the solution and also how thick the coating would be which would be based off the overall charge and composition of the paperclip and the solution. Things with a higher difference in charge would result in a thicker layer (think of it like magnets honestly, 2 STRONG magnets have a bigger field than 2 weaker magnets. If there is a large difference in charge the "field" is bigger and makes the layer thicker). This is all deducing from my head though, we aren't taught anything about the theoretical mass yield of electroplating =/

[Keel]

Really there is no...reaction...to complete. The electrolyte is dissociated in the solution and is simply attaching due to electrons and stuff, the completion of the "Reaction" is when the copper has completely covered the paperclip which would stop the reaction.

Are you sure Alex? I dont think the electolysis would stop at all!

The reaction at the electrode is given by the equation: Cu²⁺ + 2e^- --> Cu

So as long as there are copper ions and the flow of electrons keeps on going there is nothing stopping the reaction from taking place. The copper deposited simply becomes part of the electrode, copper can conduct electricity so I dont see how the reaction will not continue to take place after the copper has completely covered the electrode.

Theoretically figuring this would be impossible as far as the IB chem goes (HL has nothing on this) because it would involved the surface area of the paperclip that's in the solution and also how thick the coating would be which would be based off the overall charge and composition of the paperclip and the solution. Things with a higher difference in charge would result in a thicker layer (think of it like magnets honestly, 2 STRONG magnets have a bigger field than 2 weaker magnets. If there is a large difference in charge the "field" is bigger and makes the layer thicker). This is all deducing from my head though, we aren't taught anything about the theoretical mass yield of electroplating =/

Shouldn't the theoretical yeild, which is theoretcial becaus it ignores most of the factors you mentioned, simply be:

(coulombs) = current (Amps) x time (secs)

Number of moles of e^- = Charge (Q) / 96 500

Number of moles of Cu produced= Number of moles of e^- x 0.5

Mass of Cu= Mr x n_Cu

[dessskris]

Thank you for the suggestions!

Btw my teacher has just told us that the design is going to be on corrosion of metals, so yeah I need to change my experiment

I looked at this site and found an interesting experiment:

http://www.newton.dep.anl.gov/askasci/chem03/chem03605.htm

So I will be varying the NaCl solution concentration by varying the mass of salt I dissolve in the water.

I will use a steel plate, submerged in the solution.

If I want to still use electrolysis, if my electrolyte is 200 mL, how much voltage should be supplied? I am thinking about 4 V to 6 V but isn't 6 V too much?

Is 10 gr of the steel plate for each electrode too much? Should I just use 5 gr each?

How long should I electrolyse it? Will 30 sec be too short? Is 3 min too long?

Then after that period of time, I will filtrate the thing and weigh the residue. How is that?

That's all I have in mind I need some more feedback because the design experiment is in a few hours

[Drake Glau]

I'd use a large amount of steel if possible. Keeping the time constant means you want the corrosion to happen to the very end of however long you want it to go.

30sec will be WAY to short. 5min might even be short honestly. I'd do like 15min.

Also corrosion isn't electrolysis really. The NaCl will ionize into Na+ and Cl- at which point the Cl will go "steal" some steel and bond to it (metals are positive ions after all). This is your corrosion, the Cl taking off with the metal plate thus reducing the mass of the plate. I would mass the plate in the end, not the mass of the residue because the residue will be of the precipitate formed and that would involve finding how much steel actually bonds to the Cl-. Massing the plate and finding the difference will give you the mass of the plate that went away

If you want to do corrosion with electrolysis you would need a anode that is the same as the cation of the electrolyte. Like an iron anode with an FeCl2 electrolyte. You're forced to use NaCl which means you need an Na anode...which you probably don't have Sorry

[meoww]

Hi. I'm designing an experiment to investigate the Daniell cell but I'm kind of lost because this is something I don't know very well about I'm thinking of changing the concentration of ZnSO4 or CuSO4 or both to see its impact on the voltage.

I would appreciate if somebody can give me any further idea. My design is due on Monday already thanks a lot

Edited March 12, 2011 by Desy ♫
no text speak. type out the whole words.

[Drake Glau]

Can you give some more information? I don't know that this Daniell cell is =/

What I can say is do not change both concentrations. You never change more than 1 thing for a lab

[nuka]

oh, i got a six for my design!

basically i looked at a voltaic (electrochemical) cell.

I was planning to test different concentrations of ONE of the electrolytes, and its effect on potential difference (voltage).

for the design, the experiment doesn't have to work. it's a design for a reason.

so try something different

just make sure you have your variables and your method controls the things you can control

[meoww]

Hey thank you all for your reply. A daniell cell is a electrochemical cell and very similar to a voltaic cell. It is a zinc metal placed in a solution of zinc sulfate, connected with copper metal in copper(II) sulfate solution by a salt bridge. I think I will change the concentration of the copper sulfate to see how it changes the voltage. What I'm still wondering is what exactly happens when the concentration is changed, I mean, why does it increase the voltage?

[Keel]

Hey thank you all for your reply. A daniell cell is a electrochemical cell and very similar to a voltaic cell. It is a zinc metal placed in a solution of zinc sulfate, connected with copper metal in copper(II) sulfate solution by a salt bridge. I think I will change the concentration of the copper sulfate to see how it changes the voltage. What I'm still wondering is what exactly happens when the concentration is changed, I mean, why does it increase the voltage?

If you go back to the equation the reason should be clear.

Zn --> Zn²⁺ + 2e^-

Cu²⁺ + 2e^- --> Cu

Its a simple moles question. If you increase the concentration of the solution, you are increasing the moles of ions in the equation so more electrons can be produced. Here are some formulas for calculating the moles of e^-.

(coulombs) = current (Amps) x time (secs)

Number of moles of e- = Charge (Q) / 96 500

Number of moles of Cu produced= Number of moles of e- x 0.5

Mass of Cu= Mr x nCu

You have to be aware of the limiting reagent though, same with any moles reaction.