Jump to content

what is happening when sodium thiosulphate & hydrochloric acid react?


Recommended Posts

Hi everyone,


So when sodium thiosulphate & hydrochloric acid react what is happening in terms of bonds breaking/being made to creat the new products?


1)In the word formula we write:

Sodium thiosulphate + hydrochloric acid → sulphur + sulphur dioxide +chloride which is fine but 2NaCl is Sodium Chloride is n't it? So why do we omitt the Sodium in the wording of the products and just call it chloride?


Also what happens to the hydrogen of the hydrochloric acid? It's part of the reactants but it isn't a product?


Na2S2O3(aq) + 2HCl(aq) → S(s) + SO2(g) + 2NaCl(aq)


2Na2S2O3(aq) + 4HCl(aq) → S(s) + 3SO2(g) + 4NaCl(aq)


But back to my original question - it is the acid that is responsible for breaking the sodium thiosulphate bonds and causing the products? But the hydrochloric acid is also broke - so does the sodium thiosulphate do this?



thanks for your help people!

Link to comment
Share on other sites

ah ok, but there isn't enough oxygen on the reactants side to make 2H2O? unless we do this:


4Na2S2O3(aq) + 4HCl(aq) → S(s) + 3SO2(g) + 4NaCl(aq) + 2H2O

is this right? i think i am loosing my mind!

Link to comment
Share on other sites

sorry please ignore the above post, you lot must think i am crazy!


hydrochloric acid + sodium thiosulphate= sodium chloride + sulphur dioxide + sulphur + water.

2HCl(aq) + Na2S2O3(aq) = 2NaCl(aq) + SO2(g) + S(s) + H2O



The above is balanced and correct isn't it? Back to my original question, it is the acid that is breaking everything up?

Link to comment
Share on other sites

The above is correct, except that it is better to write ionic equations (in fact, HCl(aq) is non-existent, HCl does not simply dissolve in water, it reacts with water). Thiosulphate is the anion of the weak acid H2S2O3. This acid is very unstable, and slowly decomposes, giving H2O, SO2 and S.


A more accurate description of what happens is the following:


2H(+) + S2O3(2-) ---> H2S2O3 (this is a quick reaction)


H2S2O3 ---> S + SO2 + H2O (slower reaction, the solution turns turbid slowly)


The Na(+) ions and Cl(-) ions do not participate in the reaction, they are spectator ions.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.