Sciencemadness Discussion Board - Which element is more energetic: Aluminium or Potassium?

Which element is more energetic: Aluminium or Potassium?

TiniestChemist - 17-11-2014 at 07:26

What posseses more energy if oxidized or needs more energy to reduce or gives more energy in batteries or as heat if reacted with anything (which is all the same)? In any way, by size, by weight, per mole? Which is always overally more energetic?

Amos - 17-11-2014 at 09:17

Not entirely sure what you mean with regards to energetic, but maybe this can help some: http://en.wikipedia.org/wiki/Reactivity_series

blogfast25 - 17-11-2014 at 09:31

Quote: Originally posted by TiniestChemist

What posseses more energy if oxidized or needs more energy to reduce or gives more energy in batteries or as heat if reacted with anything (which is all the same)? In any way, by size, by weight, per mole? Which is always overally more energetic?

The oxidation of Al to alumina is accompanied by a change in Gibbs free energy that is far larger than the equivalent case of K. How much of that energy can be exploited to provide electrical energy strongly depends on cell design, though.

For simple air oxidation cells, Mg is preferred over Al, because the aluminium hydroxide is so highly insoluble, compared to magnesium hydroxide.

zed - 17-11-2014 at 14:54

Well, Aluminum is a humdinger for energy. Cheap too! Unfortunately, other factors come in to play. Al2O3 is practically insoluble under ordinary conditions. Aluminum Hydroxide isn't great either. So, Aluminum's surface is usually quickly passivated.

Ah, there. The entire depth of my knowledge on the subject!

aga - 17-11-2014 at 15:04

Quote: Originally posted by TiniestChemist

In what Context ?

What exactly do you wish to Do, and why are Al and K your chosen elements ?

j_sum1 - 17-11-2014 at 17:50

It makes a lot more sense to ask which reaction is more exothermic rather than which element is more energetic.

If you are looking at formation of oxides, then I believe you are correct. Formation of Al2O3 is probably more energetic per gram than potassium. The same is likely to be true for reaction with acids.
You then need to consider kinetics -- consider the rate of reaction in the conditions that you have chosen. For most reactions K will react to quickly to control while with Al you will have problems with it passivating.
Beyond that, it really does depend on what you intend to use the energy for. If you want something to take camping and cook your food I doubt that either material will be much use. If you want a battery then you need to come up with a design, and both elements are problematic. (Li has proved very successful however.)

Figure out your context first. Reaction second. And then you can make a sensible comparison of not just energy density but also all of the other factors that are likely to be significant. Energy content is likely to be one of the smaller factors in most cases anyway.

deltaH - 17-11-2014 at 23:39

I read a while ago that researchers working on an aluminium/hydrogen peroxide battery made the discovery that while it was known that very pure aluminium electrodes passivate and so are pretty useless, aluminium alloys don't and a sludge of aluminium oxide (hydrate?) grows over the aluminium.

I don't have a reference for you, but that should be enough information for you to track it down.

I laughed when reading about this because the researchers stated something along the lines that they would never have made the discovery were it not for their poverty and so inability to afford very pure aluminium electrodes, settling instead on commercial aluminium products lol.

[Edited on 18-11-2014 by deltaH]

j_sum1 - 18-11-2014 at 01:59

All batteries (cells technically) use redox reactions. That is what causes electron flow. You don't make much sense

j_sum1 - 18-11-2014 at 02:58

Quote: Originally posted by TiniestChemist

The zinc reacts with water

That would be a redox reaction you are talking about.

Varmint - 18-11-2014 at 03:51

First, if you are going to try and re-write electrochemical science all by yourself, you ought to consider using proper terminology.

A "battery" is, in this context, a collection of two or more connected "cells".

Now, take your last post where you decide to school everyone on what is and is not a "battery", and again I assume you mean cell:

"If something does not react when in direct contact, it is not a (cell)"

Then you go on to discount the utility of the aluminum-air (cell) by stating how poor a design it is because "The zinc reacts with water (I assume you mean air) even when you do not use them".

In the same sweeping statement you discount Li-ion and in fact all (cells).

Well, the rest of us are patiently awaiting your new definition of a battery to be put to practical use. After all, we've been hamstrung, barely able to accomplish a single thing that would require portable power because so far, what we think we have, simply does not work or is worthlessly inefficient by your standards.

I think Bert was being kind, this thread belongs in detritus.

[Edited on 18-11-2014 by Varmint]

diddi - 18-11-2014 at 04:09

if there was anything remotely sensible in using aluminium in a cell on a commercial level, don't you think it would already be in the marketplace? there has been no discussion of the difference in potential between the 2 half cells, which has significantly more to do with efficient power storage than how much energy there is in an element, whatever that is supposed to mean.

blogfast25 - 18-11-2014 at 05:56

Quote: Originally posted by TiniestChemist

If all scientists thought like you, nobody would ever discover anything new. And, no I don't think so. Even electricity is just recently discovered. Few hundred years ago only, semiconductors even more recently.

True but the path to Al based batteries has already been beaten to death. And someone with such scant knowledge of chemistry as yourself will not make the breakthrough needed, trust me.

At least familiarise yourself with all prior part, before you go off on a wild goose chase.

Bert - 18-11-2014 at 11:29

The whole thread... Reminds me so much of a few others recently. Border line trolling.
Somehow, with very much the same writing style- Although posted under several very recently registered screen names. A persona that alternately seems ignorant and enthusiastic, then just a LITTLE too knowledgable about chemistry & technology to have credibly posted the original topic.

Does anyone else see a resemblance between this and other threads/posters?

aga - 18-11-2014 at 11:41

I can't point a finger at an example at the moment, but Yes, it looks and feels similar to several others i've read.

To be totally clear, this one doesn't conform to what i feel to be a standard format/look-n-feel, so may be of the Ilk rather than of a Clan.

[Edited on 18-11-2014 by aga]

gdflp - 18-11-2014 at 12:42

Quote: Originally posted by Bert

Charcoal is capable of performing the reduction of Iron ore with only natural draft. IF you are really clever/experienced at building & running the furnace.

Original poster: I don't like your name.

That's why your name is changed. BTW does anyone think this could be another reincarnation of PHDchemist?

phlogiston - 18-11-2014 at 14:43

Yes, it was my first thought as well.
Also note his current mood. There was someone that recently registered with the t***chemist nick a few days ago, possibly the same person. Woelen asked him very politely to change the nick.

[Edited on 18-11-2014 by phlogiston]

Etaoin Shrdlu - 18-11-2014 at 15:42

He seems to like deleting all his posts but the tops of his threads.

gdflp - 18-11-2014 at 15:52

Quote: Originally posted by phlogiston

Yes, it was my first thought as well.
Also note his current mood. There was someone that recently registered with the t***chemist nick a few days ago, possibly the same person. Woelen asked him very politely to change the nick.

[Edited on 18-11-2014 by phlogiston]

That person is one and the same. Bert changed his name because he didn't like it.