[deciple77]

Hi, I am an engineering student who needs help finding a chemical reaction for a class project.  We were assigned to design and build a miniture car that is propelled by a chemical reaction.  My initial reaction is to find a combustion reaction or an acid base reaction, but I want something orignal that no one else is likely to use. I figure any reaction that releases a significant volume of gas will do the job, but my limited experience in chemistry does not provide me with a reaction that is adiquite and safe.
Any sujestions?

Thanks
Deciple

[jdurg]

I think the only reason I'm saying this is cause I'm on a chlorine generation binge right now, but you could take some solid calcium hypochlorite and add concentrated hydrochloric acid to it.  The gas that comes off would be chlorine gas which you could use to move a spoke on a wheel, or perform some type of propulsion.  Any excess gas could be bubbled through an NaOH solution, thus forming chlorine bleach.  heh.

[Limpet Chicken]

If the chlorine reaction was on a big enough scale, might it not lead to heating of the NaOH?
hypochlorite is produced from Cl+NaOH only when quite cold, at higher temperatures, the reaction produces entirely the chlorate salt instead.

Jdurg, for making Cl, I reccomend dripping conc. HCl on to KMnO4, that is the method I use to generate all of the Cl that I use, Cl evolution is fast and in large quantities.

I imagine that would also corrode the spoke/engine like nobodies buissiness (and smell bad )

[jdurg]

Well, I've found that calcium hypochlorite and HCl works very well for generating chlorine.    The water that's inside the HCl will cause some chlorine to be generated when it hits the hypochlorite, and the acid will cause the hypochlorite to decompose into chlorine gas.  As a result, a great deal of chlorine gas is generated.  However, in the long run all this chlorine gas generation will be for naught as my friend is working on getting cylinders of liquified chlorine gas for use in making chlorine ampoules.  The cylinders should be a lot easier and safer than the current methods of generation.  

[billnotgatez]

Chlorine is smelly and is not a very safe gas. Using baking soda and vinegar to produce carbon dioxide would be safer.

On the other hand if you are allowed to be slightly unsafe and want a hoot – build a small wood car from a kit (there are several used by kids for contest) and put a small rocket motor on it (those are found in hobby shops). It will scoot right along. Might need a foam barrier to catch it at the other end or pop a parachute.

http://www.usahobby.com/pinecar/blocks.html
http://www.redarrowhobbies.com/estes_engines.htm

Depending on how complex you want to get based on how well stocked the lab is you can do hydrogen from HCl and a metal. Then you could use it for a small jet engine.


Back to safe – I think you might be able to get sufficient electricity out of a lemon juice reacting with a metal.

http://www.hilaroad.com/camp/projects/lemon/lemon_battery.html

Of course a batter of any kind is a chemical reaction. So a hunk of wood with toy wheels, an electric motor, and battery, will meet the criteria. Or one of those radio shack remote control cars.

Regards,
Bill

[deciple77]

I think I want to experiment with HCl.  Where is the best place to get it and is there a cirtan metal that works beter than another?

Thanks
Deciple

[Limpet Chicken]

HCl of 16% to 30% conc. is available cheaply as a rust remover/pathcleaner, I buy mine in   1 gallon plastic bottles for a few pounds in the UK.

Distillation at a low temperature would serve to concentrate the HCl to a far greatert degree, I need not add, take care not to come into contact with the HCl, or breathe the fumes in.
Although the 16% conc. wont cause immadiate pain or anything short of mild redness, make sure you wash it off.

[jdurg]

The strongest concentration you can get from distilling HCl is ~20%.  At that concentration, it forms a constant boiling mixture (azeotrope) which means that you are no longer able to distill it by normal methods.  Chances are, if you buy some HCl it will already be at a stronger concentration and distilling it will just weaken it.  

[Donaldson Tan]

I don't think chlorine gas is suitable for the job because of its corrosive nature, plus it's a hazard in itself. You probably will need additional protective measures to prevent your miniature car from breaking down under the action of chlorine on it, plus protective gears for yourselves.

I was thinking along the line of solid sodium nitride. Action of heat will produce nitrogen gas fast. Nitrogen gas is inert and the rate that it is being produced should provide more than sufficient power to drive the car. Nitrogen is also an environmental friendly gas, so you need not worry about toxic emmissions too.

[deciple77]

this solid sodium nitride intrigues me, Is it something an average person like myself can get my hands on, and if it releases the nitrogin does it leave elemental sodium and isnt that reletavly unstable?

Thanks
Deciple

[Donaldson Tan]

I had meant sodium azide, not sodium nitride. It is employed in the emergency inflation of airbags in your vehicles.

It breaks down under heat according the following equation:
3NaN₃ -> Na₃N + 4N₂

I think you've to source the Material Safety Data Sheet (MSDS) for NaN₃ and Na₃N yourself. You would need these information to confirm if sodium azide is the best fuel for your car.

[movies]

I like geodome's idea of using an N2 source.  Do be careful with sodium azide though, it is shock sensitive and may explode.  In fact this reaction may be a little too violent for your purposes, but you might be able to tame it somehow.  Maybe you could just make a solution of NaN3 in some organic solvent and heat it a little.  That would probably avoid the shock sensitivity issue.

[deciple77]

Ok, I did a little reading on sodium azide.  It sounds very dangerous, but it seems that it could provide the type of reaction I am looking for.  Can someone discribe to me how to handle it and achive the desired reaction, and how do I ensure that it only releases N2 and not other leathal gasses.  I am preforming this reaction for a groupe of college students and I would prefer not to kill anyone.  Remember I am an engeneering student not a chemist.

Thanks
deciple

[movies]

I don't think NaN3 is terribly, terribly dangerous, just don't drop it or hit it with a hammer or anything.  If you can keep the solution basic then you should avoid the production of ammonia, but you might actually be better off letting the ammonia form.  If you have an aqueous solution you should be fine.

I don't know the specifics of what is required to liberate N2 from NaN3, maybe geodome can shed some more light on that.  There may be a safer way than heating it, but I don't know.

[Demotivator]

Hey guys
I had some old sodium azide solution sitting in a refrigerator. I figured mixing it with hydrogen peroxide could yield safe nitrogen and oxygen gas.
So I mixed it with cold 30% H2O2. The reaction started slow, then got hot with lots of gas evolution.
Adding azide solution to solid sodium peroxide works too.