Al+CuCl

[racegirl3711]

After the copper is formed, there is a precipitate left over i think this is Al(OH)3 but i can't explain why any help?

also, why does it release hydrogen gas?

[big314mp]

After the first reaction, you have AlCl3 and Cu metal. The Cu metal is accounted for, so we can ignore it.

 

As for the AlCl3, consider what happens when we dump that in water. The Al3+ ions will bond to the OH- ions producing your precipitate.

 

As for the hydrogen, I think you mean hydrogen ions (H+). This is explained by the dissociation of water. Water dissociates into H+ and OH-. The OH- is sucked up by the Al3+, leaving behind the H+.

[John Cuthber]

Al reacts with water to give H2 and "Al(OH)3".

[big314mp]

I was under the impression that Al reacted with acids to give H2, not water.

 

http://en.wikipedia.org/wiki/Activity_series

[YT2095]

the ppt will be copper metal, AlCl3 may undergo Partial hydrlysis if you have enough water, and that will form a little HCl.

the Hydroxide of Al will be like a jelly, and you`r unlikely to see a ppt of it, more you`ll notice the liquid get thick and viscous and perhaps a little turbid.

[John Cuthber]

Al will certainly react with water- quite vigorously. Normally it doesn't because there's a layer of oxide in the way. The CuCl (I bet that should be CuCl2) disrupts this layer.

Mercury does an even better job- but is rather more toxic so it's not generally done as a school experiment.

The true story is a whole mess of equilibria between hydrated Al+++ species and Cl-.

[big314mp]

Al will certainly react with water- quite vigorously. Normally it doesn't because there's a layer of oxide in the way.

 

So when looking on that activity series, is Aluminum listed lower because it takes some extra effort to get through the oxide layer (i.e. acid)? This series says that aluminum will react with hot water, so is that because of disruption of the oxide layer as well?

 

http://www.chem.vt.edu/RVGS/ACT/notes/activity_series.html

[John Cuthber]

The reactivity series is a bit of an oversimplification. If they had drawn the cutoff so that Al was listed as one of the metals that react with water then we would all be happy. From the point of view of the energy released Al certainly reacts with water and that's the viewpoint often taken in such series whern you look at the more sophisticated version (where numbers are put against the metals, so it's not just a rank but a measurement scale) .

http://en.wikipedia.org/wiki/Table_of_standard_electrode_potentials

[YT2095]

Mercury does an even better job- but is rather more toxic so it's not generally done as a school experiment.

 

Using Gallium instead of mercury is the safer method.

[big314mp]

I guess I should've looked at the Table of reduction potentials in the first place. I figured that the Activity Series was based on that.

[nitric]

Using Gallium instead of mercury is the safer method.

 

that would be safer but it would be quite difucult to find a resonable amount of gallium for a resonable price