(salt)water electolysis

[m_ice]

I'm doing water electrolysis, i have got the appartus from the lab. I used electric adapter converts AC to DC and vise versa...What i realized the procces is too slow like it will take day to seperate hydrogen and oxygen, any reason why? So, i used salt as catalyist and the constant was 20 min.

I have done 3 experiments to see the effects on effeciancy on electrolysis: using different rods, temprature of water, and voltage.

 

I wanted to measure the amount of hydrogen that is in tube?? ANYONE KNOWS HOW..

And anyone knows any other reason why the color of water changes other than salt?

what i think but im not sure, the rod is also taking reaction not only salt, if that true then that will effect my result, and i dont want that to happen...I NEED HELP in this what should i do????

 

THANX

[ski_power]

You said you used salt as a catalyst...that's exactly it. It goes faster coz salt is a catalyst.

Well actually water (pure) is a very bad conductor of electricity only 1 in 10^14 molecules dissociate. But when you add an ionic compound (salt, NaCl), it ionizes in water as Na+ and Cl- ions, hence readily conducting electricity, and thereby increasing the speed of electrolysis.

You could also increase the speed of electrolysis by increasing the current. There's a set of rules that I dont quite remember,

W=Zit,

W = weigh of substance deposited, I= Current passed, T= time in seconds, and Z=E/F, where E= Equivalent weight of (err...i forgot, but I think it's the electrode), F=96500 coulombs...

So Z= electro chemical equivalent of metal.

 

Using this formula, you can calculate anything you want...

 

To measure the amount of Hydrogen, there's a really simple but cheap technique.

Let,

W1=Weight of empty tube; W2=Weight of Tube containing hydrogen.

 

therefore mass of hydrogen=W1-W2.

And to find STP volume you could always use

1 mole=22.4 Lit

2.00016 gm H2 = 22.4 Lit.

x gm = y lit.

 

y=22.4 * x/2.00016

 

About the colour change even I dont know, is it the liberation of Cl2 gas???? I have no idea.

[jdurg]

Yes, the color change is the liberation of chlorine gas. Chlorine gas is fairly soluble in water, and even more so in an alkaline solution of water. When you are electrolyzing the salt/water solution, you are forming chlorine gas and sodium hydroxide. These two react and give you sodium hypochlorite (Bleach) which will further react due to the electrolysis forming a bunch of other stuff as well. You may be able to use sodium carbonate, or sodium bicarbonate as your electrolyte as that will create carbon dioxide gas and not chlorine gas. That would make a 'cleaner' solution.

 

Also, what type of electrode are you using? Platinum is the best electrode to use, but a might bit expensive. Pure Graphite is another good, and inexpensive, electrode. Anything else will undoubtably react with the reaction going on.

[m_ice]

i'm the rods that im using that is Aluminium, Copper, and Iron...and i found that iron is most effeciency one, anyone the reason why??

But what i want to know is the reaction effect with my results or it only effects the amount of oxygen, Cuz my aim is to find the amount of hydrogen.

 

I think "ski_power" made a mistake in finding the amount of hydrogen, it should be

H=W2-W1 cuz the answer must be postive number. Any way do u have any other easy way of calculating the amount of hydrogen.

 

What actually happens when i used salt, does it Na and Cl seperate as hydrogen and oxygen, or it will participate?..

[m_ice]

By the way what is that unit "gm". And can anyone explain to me Faraday's law..

What is the difference/relation between Ampere and Volt? If use 9V can i know how many ampere is that?/

[ed84c]

R=V/I

 

Ressistance= Voltage/ Current. Work it out from there.

[calbiterol]

But what i want to know is the reaction effect with my results or it only effects the amount of oxygen, Cuz my aim is to find the amount of hydrogen.

 

... What?

 

I think "ski_power" made a mistake in finding the amount of hydrogen' date=' it should be

H=W2-W1 cuz the answer must be postive number. Any way do u have any other easy way of calculating the amount of hydrogen.[/quote']

 

Actually, I'm pretty sure both of these have issues. Because hydrogen is lighter than air, both values are going to be directly related to hydrogen's displacement of the air around it. The mass that you would obtain, Ice, will be negative. The opposite of this (multiply it by -1) is the mass of the displaced air. (By the Archimedes Principle) In order to calculate the mass of the H₂ produced using that method, you'd have to know the volume and the density, and do a series of calculations... At that point, it's much easier just to look up the density of it, and measure the volume.

 

By the way, do you mean mass or volume? You said amount, and both mass and volume are quantative measurements.

 

What actually happens when i used salt, does it Na and Cl seperate as hydrogen and oxygen, or it will participate?..

 

... Pass that one by me again, I couldn't understand it at all.

[m_ice]

Actually i found it, i used this equation to find the ampares in certain period of time:

Columbus= Ampare * Seconds

 

I want to know what reaction is taking place when i add salt to the water (what happens to oxygen, hydrongen, and NaCl)??

[ed84c]

NaCl when dissolved becomes Na+ and Cl- i.e. it splits up and ions float around in the water.

 

These ions, being charged, help a current flow through the water.

 

When this happens, the Hydrogen, gets an electron at the Cathode (it gave 1 electron of its to oxygen) and becomes H2 gas. The opposite happens at the Anode.

[m_ice]

i found this it might be helpful:

 

number of hydrogen atom=6.24*10^18 e-/ coulomb * I * t

 

t is in seconds

[m_ice]

I didnt get the STP volume and what is the "gm"??

[akcapr]

the water went yellow due to the many compunds iron formed during the elctrolysis, Such as Iron Oxide. Thats what made the water chnage colors.

[Guest derforscher]

dude! use an eudiometer to measure the H2. they're mad fun. i like making H2 balloons and blowing them up with Mg twisted into toilet paper.

[jdurg]

the water went yellow due to the many compunds iron formed during the elctrolysis, Such as Iron Oxide. Thats what made the water chnage colors.

 

akcapr, open up a bottle of bleach and tell me what color it is. Now look at some piles of rust and tell me what color that is. Do you honestly believe that Iron oxide, which is insoluble in water, will turn the water a yellow color? The yellow color is caused by the dissolution of chlorine gas into the water and the presence of sodium hypochlorite which forms as the chlorine gas dissolves in the forming sodium hydroxide solution. An equillibrium is achieved where some free elemental chlorine always remains dissolved in solution. (Hence the reason why chlorine bleach is yellow in color).

[akcapr]

trust me, ive done it before wen i was making fe2o3- it turned yellow, im not colorblind i dont think.

[akcapr]

but then again, it is possible that the fe2o3 didnt cause the color, what you are saying may be right.

[akcapr]

also last time i checked, hypochlorite bleach was white. And, have you ever made are had iron chloride in solution, the color is yellow.

[m_ice]

All what i want is to find the amount of hydrogen produced (% of the test tube that filled up)...

 

Is there an hydrogen electrode..sounds weird.. cuz i read in website this: "The bubbles from the hydrogen electrode were larger than the bubbles from the copper and aluminum." or maybe i have misunderstood the sentence...

[ski_power]

Actually dumb of me,

it was W2-W1.

and gm is grams.

the amount means mass, because we are weighing both the containers( or both the cases).

 

Don't we use downward displacement of water to collect hydrogen? So you could simply use maths, total volume of test tube - (pi*r*r*h)

 

r=radius of tube, h=height of tube occupied by gas.

 

That's the simplest i can think of now.

[calbiterol]

Ski power, like I said before, w2-w1 is not going to be its mass, because hydrogen is lighter than air. It is going to be the displacement of the air (or whatever medium you mass it in), unless you mass it in a vaccum, which is impractical. If you are measuring the amount of water being evacuated from a submerged test tube, then you must take the pressure of he water into account if you want a truly accurate value.

 

Ice: the "hydrogen electrode" they are refering to is the electrode where hydrogen is gathering at, in other words, the anode (negative electrode). The bubbles there are bigger due to the fact that water is H₂O - two hydrogen atoms to one oxygen atom. Since both hydrogen gas and oxygen gas molecules are diatomic, there will be a theoretical 2:1 ratio of hydrogen to oxygen.

 

If you just want to know the percent of the test tube filled, why don't you just use a graduated cylinder as your test tube? then just read how much is devoid of water. Your measurements will be a little off because of the water pressure, but it should be a persistant error - all measurements should have it. As long as you don't want the actal amount of hydrogen, and are just using the amount for comparison, then you should be fine.

 

Lemme know if you need any clarification on anything I said.

[akcapr]

also, how in the world would a person like you be able to weigh the gases accurately? So just do it like calbiterol said.

[calbiterol]

Actually, it would really just be the "relatively simple" technique of applying the Archimedes Principle to the displacement of the water in the closed system (the test tube completely submerged in (salt) water. Find the density of the water (if it isn't distilled) and the mass of the overall system before the reaction and it's relatively simple from there. After the reaction is done, find the change in mass - this is the mass of the displaced water - and calculate the volume from the density of the water. Archimedes in action.

 

So much for simple it's a logistical/practical nightmare. I've tried similar things, although with very, very small quantities of the (unknown) substance being massed. Bloody near impossible to get accurate measures at that small of a scale. If the reaction is producing enough hydrogen, though, it shouldn't be too much of an issue.

[ski_power]

Oh yeah my mistake,

then I guess we'll have to improvise with the extremely simple method that calbiterol told us

[m_ice]

Still i didnt understand anything, everyone say different thing. All what i wat to know is the reason of color and the electrods reaction. As i said im using aluminium, copper, and iron as electrods and salt as catalyst..

Plz also use chemical equations..