Formula for Sodium Thiosulfate: Na2S2O3 - Jules

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The formula for Sodium Thiosulfate is Na2S2O3, which is derived from Sodium Sulfate (Na2SO4) by replacing one oxygen atom with a sulfur atom. The confusion arises from the interpretation of "thio," which indicates the presence of sulfur. The correct formula reflects that there are only three oxygen atoms, not four, as incorrectly suggested by Na2S2O4. Additionally, the oxidation state of sulfur in Na2S2O4 would be +3, which is not a valid oxidation state for sulfur. Understanding these chemical principles is crucial for accurately determining the formulas of compounds.
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How would I figure out the formula for Sodium Thiosulfate?

I was asked that question on an exam and I knew sodium sulfate was Na2SO4, so I figured ok, thio means sulfur, so I'll just add another S like this:

Na2S2O4

But my prof said Na2S2O3
was the right answer, and I have no idea how I was supposed to know there were only 3 O's, since it's not sulfite.
Wikipedia agrees with him, tho.

Any ideas?

~Jules~
 
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You're replacing an Oxygen atom with a Sulfur atom. The original compound is Sodium Sulfate, which is Na2SO4, but when it becomes Sodium Thiosulfate, one of the Oxygen atoms is replaced with a Sulfur atom. So it becomes N2S2O3.

If it were to be Sodium Dithiosulfate, you would replace 2 Oxygen atoms with 2 sulfur atoms, so it would be N2S3O2
 
Jules18 said:
How would I figure out the formula for Sodium Thiosulfate?

I was asked that question on an exam and I knew sodium sulfate was Na2SO4, so I figured ok, thio means sulfur, so I'll just add another S like this:

Na2S2O4

But my prof said Na2S2O3
was the right answer, and I have no idea how I was supposed to know there were only 3 O's, since it's not sulfite.
Wikipedia agrees with him, tho.
Also, consider that in your formula: Na2S2O4 sulfur would have oxidation number = 3, which doesn't exist (for sulfur).
 
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