[Brad]

Can electrolysis of water be used to verify the difference in total power output of 2 test circuits.
\i.e. The more gas produced means the more total power that was sent to that circuit? Brad

[jubba]

I think you definitely can.
1. Find the energy released in electrolysis in a data sheet and express in terms of joules per moles of hydrogen or oxygen gas
2. Measure amount of oxygen or hydrogen gas produced for a fixed time period.
3.Using previously derived expression calculate energy. Divide by time in seconds to obtain power.
Voila

[Donaldson Tan]

you can only verify which circuit produced more power, but not actually measure it. this is because not all electrical energy is used to electrolyse water. some of this energy heats up the water.

A simpler and effective way is to measure the output using a multi-meter.

[Brad]

1st  SORRY for a late responce and Thanks for the info. To help clearify, the reason for the electyrolysis test is, in fact, to verify the accuracy of a meter..

Note:The following numbers used are for simplfication only and to help make this clear in my mind----

If in our experiments we used a "fully charged" 1 "faraday" capacitor as the power input for both test circuits:

 Test 1: The capacitor is "fully" discharged intoTest circuit A and converts 1 CC of water into gas,

 Test 2: The capacitor is "fully" discharged into Test circuit B  and 1.5CC of water is coverted into gas.

Is it logical to assume that Test B is approx 50% more effecient than Test A?

Please HELP. I have a wager with an Electrical Engineering instructor for a possible "A"..Thanks Brad

[Borek]

Is it logical to assume that Test B is approx 50% more effecient than Test A?

Logical - yes. Precise - not without detailed analyze of chemistry taking place. Depending on the circuit setup, voltage used, current used (AC or DC) and composition of the electrolyte you may see almost 100% of charge converted to gas or no gas evolving at all.

[Brad]

Borek Thanks for the help.
With part of your responce, I like some clearification concerning using either AC or DC with the electrolysis experiment.

With all other parts of the experiment being equal
My question is: Will not the same amount of gas be produced by 1 watt AC as compared to 1 watt DC? If I remember correctly, they both will produce equal amounts of heat in a bombcalorimeter.... If this is not so what is the typical average gain or loss for either concerning gas production?

[Borek]

Gas - be it oxygen or hydrogen - evolves only if the potential applied is above some threshold level. With AC you have potential high enough only through part of the cycle. At the same time in case of AC part of the energy will be used in every cycle to charge/uncharge double layer forming on the electrode surface (effectively just heating the solution). Thus in AC the power used can have no link to the volume. With DC situation is less complicated, but still you must precisely control conditions.

Many years ago charge was sometimes measured by means of mercury electrolysis - in controlled conditions (voltage, low amperage, precisely selected composition of electrolyte) in thin pipe mercury was transferred from one electrode to the other - both electrodes were made of mercury and you could measure length of the mercury electrodes with simple ruler.

[Brad]

Thanks Borek-GOOD INFO!!!!!!

If I understand correctly, Is AC far less efficient with the electrolysis of water when compared to  DC?

[Borek]

Yes.

[Brad]

Borek--What I like, a simple answer.... Thanks to you guys Im half way to winning a bet.  This forum makes chemistry cool...GOOD SHOW!!!!


Thanks Brad

PS You aint heard the last of me yet.

[Cavalier]

Dear Borek:

With the same idea.  I want to cook a container full of organic viscous cotton.  If I place two plates on two sides of the box, and run alternating current (AC), can I heat up this material.  The box is 25 xm x 25 cm x 25 cm.  Can I cook it to a point where it is steaming hot?  I have access to a 380 Volt, 3 phase AC source.

Thank you in advance for everybody who responds to this post.

Roger RC

Gas - be it oxygen or hydrogen - evolves only if the potential applied is above some threshold level. With AC you have potential high enough only through part of the cycle. At the same time in case of AC part of the energy will be used in every cycle to charge/uncharge double layer forming on the electrode surface (effectively just heating the solution). Thus in AC the power used can have no link to the volume. With DC situation is less complicated, but still you must precisely control conditions.

Many years ago charge was sometimes measured by means of mercury electrolysis - in controlled conditions (voltage, low amperage, precisely selected composition of electrolyte) in thin pipe mercury was transferred from one electrode to the other - both electrodes were made of mercury and you could measure length of the mercury electrodes with simple ruler.

[Borek]

No reason why AC should not work. Main problem can be resistance of the solution, as it limits the current.