nothing is really truly irreversible

Theoretically. In practice, its quite a hassle.

 

How would you determine this from the equation?

I think the answer is, you would need specific knowledge about the products of the reaction. However, that knowledge is not, a priori, inherent in the reaction equation itself.

A chemical engineer in the battery industry might be able to do this on inspection, but not just anyone.

So, look at the equation to determine the products, then look up the properties of the products related to their response to an applied voltage when they are in the specific mixture they will be in at the end of the reaction. Determine the reverse equation, then see if this gets you back to where you started.

Easy as pie!

 

I dont know what kind of pie you eat..

 

Keep in mind that charging a battery is adding lost "energy" NOT reversing the discharge process.

Another point from the 'ageing' of batteries is that, with lead-acid at least, much of the long term degeneration is mechanical not chemical.

A better example for the reversible reaction may be the NiFe cell - they last just about forever. (Nickel & Iron plates with potassium hydroxide electrolyte).

http://en.wikipedia.org/wiki/Nickel-iron_battery

That article is wrong on the history side - they were used in the UK for electric traction batteries in things like milk floats and trolleybuses, and manufactured at least through the 1960s. One of the latter uses was miners/cavers cap lamp batteries, with the battery block worn on the belt.
They are probably still made for long life applications.

Edit: Yep, a quick google search shows places selling new ones, eg.
http://www.beutilityfree.com/content/index.php?option=com_content&view=article&id=44&Itemid=129

 

I believe energy and entropy gets in the way of reversable reactions. You can put a nail in the earth and it will become iron oxide, but you can't take iron oxide and spontaneously turn it into a nail. Energy is required to do that. On the other hand, if you supply the energy the reaction is reversable.

Take the case of a refrigerator. You can make heat create ice, but can you make ice create heat? If the latter were the case then Alaskans would be sitting on a source of energy.

 

Actually usable power could be defined as a differential in energy levels. If everything were the same temperature then you would have no energy to tap off of. If it were hot, then ice would be a source of energy, in the form of a sink to move the energy into.

 

You can indeed use ice to make heat.

 

Pelter effect. Heat makes cold and energy, Energy makes heat and cold, Cold produces heat and energy.

http://www.wisegeek.com/what-is-the-peltier-effect.htm

 

There is a statement by Einstein (or maybe Newton, I am not going to look it up) that says that the total product of mass and energy will always stay the same I think space stuff was not thought about. This in effect means that the end result of all chemical and/or other reactions is nul. You burn coal in a furnace, you heat water to high temperatures to produce steam to drive turbines to make electricity. The measured electricity power compared to the burning coal is maybe 20%. Take the 20% and add the losses in the power station and you have 100%.
You cannot reverse this action!!!
And by Einsteins law, the total energy of the process remains at 100%
You need more, we talk

 

No, you cant reverse it in the sense of a battery.

But in the realm of physics, the elements will revert to their original states eventually (few billion decades maybe )

 

But in the realm of physics, the elements will revert to their original states eventually (few billion decades maybe )

Yeah, when protons decay (t1/2 >6.6X10E33 years). I'm not worried at the moment about that happening.

John

 

I have debated both sides of this argument over the years.
Still dont have a grasp on it.

in our environment, if we remove heat, we are left with cold.
If we remove cold, are we left with heat?

does an air conditioner produce more heat or cold?


If light energy is removed, we have dark.
how do we remove the dark without the use of energy?

Is there such a physical thing as dark energy?



it reminds me of the famous? quote by Henry Chinaski:

Henry: This is a world where everybody's gotta do something. Y'know, somebody laid down this rule that everybody's gotta do something, they gotta be something. You know, a dentist, a glider pilot, a narc, a janitor, a preacher, all that.
[sighs]
Sometimes I just get tired of thinking of all the things that I don't wanna do. All the things that I don't wanna be. Places I don't wanna go, like India, like getting my teeth cleaned. Save the whale, all that, I don't understand that.
Jim: You're not supposed to think about it. I think the whole trick is, not to think about

 

I have debated both sides of this argument over the years.
Still dont have a grasp on it.

in our environment, if we remove heat, we are left with cold.
If we remove cold, are we left with heat?

Cold is the absence of heat, which is molecular vibration.

does an air conditioner produce more heat or cold?

More heat, but it moves heat around.

If light energy is removed, we have dark.
how do we remove the dark without the use of energy?

Dark is the absence of light, it does not need to be removed.

Is there such a physical thing as dark energy?

Yes.

Rhetorical questions answered free of charge.