[lightarrow (OP)]

What happens mixing diluted H₂SO₄ to a water solution of Na₂S₂O₃?

Edit: Sorry, I wrote Na₂S₂O₄ as a mistake. It's corrected now.

[DrDick]

from the Wikipedia article on sodium thiosulfate:

Thiosulfate anion characteristically reacts with dilute acids to produce sulfur, sulfur dioxide and water:[1]

    S₂O₃²⁻(aq) + 2H⁺ (aq) → S(s) + SO₂(g) + H₂O(l)

So it's not that it needs sulfuric acid - any acid will do.  Sulfuric acid can act as a weak oxidizing agent in the right circumstances, but this isn't it.  In fact, the thiosulfate ion is actually its own oxidizing and reducing agent in acid.  The two sulfur atoms exist in different oxidation states, with an average of +2.  One sulfur atom then goes to +4 while the other goes to zero.

Dick

[lightarrow (OP)]

from the Wikipedia article on sodium thiosulfate:

Thiosulfate anion characteristically reacts with dilute acids to produce sulfur, sulfur dioxide and water:[1]

    S₂O₃²⁻(aq) + 2H⁺ (aq) → S(s) + SO₂(g) + H₂O(l)

So it's not that it needs sulfuric acid - any acid will do.  Sulfuric acid can act as a weak oxidizing agent in the right circumstances, but this isn't it.  In fact, the thiosulfate ion is actually its own oxidizing and reducing agent in acid.  The two sulfur atoms exist in different oxidation states, with an average of +2.  One sulfur atom then goes to +4 while the other goes to zero.

Dick

Thank you. I indeed imagined a dismutation could happen; you have confirmed it. That is a way to produce colloidal sulfur particles in water for experiments in optics.

[DrDick]

Actually, I believe that was the next line in the Wikipedia article.   []

Dick

[lightarrow (OP)]

Actually, I believe that was the next line in the Wikipedia article.   []

Dick

That's true. I had only read the italian version. Thank you.