Sciencemadness Discussion Board

Reverse precipitation reaction

cnidocyte - 24-8-2010 at 12:37

For example how would one go about producing SnCl2 from SnO2 an NaCl?

Lambda-Eyde - 24-8-2010 at 12:39

That would be next to impossible by conventional means, if I'm not mistaken. Reacting SnO<sub>2</sub> with HCl should yield SnCl<sub>2</sub>.

Mr. Wizard - 24-8-2010 at 12:52

At the risk of explaining something you probably already know; every possible reaction takes place, even the one you just mentioned. The reason you don't see it as a 'product', is it's opposite reaction takes place more often. If you can find a way to separate the two products you can add energy to the system and perhaps even get the product through some physical process. This 'one way' valve or trapdoor can be crystallization, turning to a gas and leaving the mix, or other processes.

cnidocyte - 24-8-2010 at 14:46

Thats a good analogy, a 1 way valve. Makes the concept a lot easier to think about.

bbartlog - 24-8-2010 at 15:31

Don't overestimate the potential of one-way valves. E.g. I seem to recall a suggestion that HCl could be produced from citric acid plus NaCl (after all, the HCl escapes as gas!). Doesn't really work.

In your case I think two ways are
A) reduce the SnO2 to elemental tin by extreme heat, then use it as an anode for the NaCl
B) electrolyze the NaCl, use the chlorine to produce HCl, react that with the SnO2.

None too practical, really. Just buy some HCl (unless it's restricted where you are).

Actually I see you want SnCl2 so you are also looking to reduce from Sn(IV) to Sn(II)... that makes things a little more complicated.

Mr. Wizard - 24-8-2010 at 19:29

"Don't overestimate the potential of one-way valves"

I won't, I was just trying to give a 'real world' model. I find them helpful myself, even though they don't really sound 'scientific', and are over simplified, they explain a concept. The opposite would be a formula with no model. First the concept and then the math, for me it works like that.

Since SnO2 is a conductor, perhaps an Anode could be made out of it by melting it (1630C) and the anode converted by electrolysis of an NaCl solution and the Chlorine liberated to SnCl2 hydrate solution. I have no idea if this would actually be feasible. Keeping the NaOH generated at the cathode away from the product would be desirable.