[cimon9999]

Hi,

You may have heard of the efforts by researchers at Purdue to develop Aluminium-Gallium as an electricity storage mechanism to power cars: http://www.purdue.edu/UNS/x/2007b/070827WoodallNanotech.html

This works by placing the Al-Ga in water and Hydrogen is evolved. I'm looking into this area in university. Chemistry is not my subject area (it's mechanical engineering) so that's why I'd like you to check over my figures, if you would.

Since we'll be testing it in a lab, we only want to evolve a small amount of H₂ namely 100cc or 1X10-4m^3. This will be at STP so that's 100/24000 = 0.0041667moles.

The equation for evolution of hydrogen is: 2Al + 6H₂O > 2Al(OH)₃ + 3H₂ - 199.6kcal

So the required aluminium to produce this is (2/3)*(0.0041667)moles, or 0.002714 moles, correct?

Is it also correct to say that the exothermic heat given off becomes (0.0041667/3)*(-199.6kcal)= -0.2772kcal?

The mixture I'm proposing to try is 75% by weight Al and 25% by weight Ga which would mean (0.002714)*(26.981)g Al, or 0.074775g Al & 0.024925g Ga? So that's a mixture weighing 0.0997g if my figures are correct.

Seems mighty small to me, but apparently that's going to be made in a crucible. Any light you could shine on the feasibility of such a feat would be much appreciated. If you could suggest a method to measure the heat given off in the reaction accurately also (since this, too, seems very small), that would be perfect!

Thanks a lot,
Eamon

[Borek]

This will be at STP so that's 100/24000 = 0.0041667moles.

The equation for evolution of hydrogen is: 2Al + 6H₂O > 2Al(OH)₃ + 3H₂ - 199.6kcal

So the required aluminium to produce this is (2/3)*(0.0041667)moles, or 0.002714 moles, correct?

(...)

The mixture I'm proposing to try is 75% by weight Al and 25% by weight Ga which would mean (0.002714)*(26.981)g Al, or 0.074775g Al & 0.024925g Ga? So that's a mixture weighing 0.0997g if my figures are correct.

Numbers look more or less correct, depending on the STP definition used. 100 mL of gas and 270 cal of heat looks reasonably in the range of things that can be easily measured. Coffe cup calorimeter should do the trick.