Does the reaction of sulfur and potassium nitrate involve production of sulfur trioxide? [duplicate]








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[What are the reaction products of sulfur and potassium nitrate?](/questions/42800/what-are-the-reaction-products-of-sulfur-and-potassium-nitrate)

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I've heard that oxidising sulfur with potassium nitrate yields $\ce{SO3}$ gas, but can't find a definitive answer anywhere.


Is sulfur trioxide produced? More generally, what's the full reaction?




If we talk about the reaction of *only* sulfur and potassium nitrate, then the reaction yields potassium oxide, sulfur dioxide and nitrogen.


$$\ce{4KNO3 + 5S -> 2K2O + 5SO2 + 2N2}$$


However, when carbon is added in the form of charcoal, then the resulting mixture is called [gunpowder](https://en.wikipedia.org/wiki/Gunpowder). The overall chemical reaction of gunpowder is as follows:


$$\ce{2 KNO3 + S + 3 C -> K2S + N2 + 3 CO2}$$


$$\ce{10 KNO3 + 3 S + 8 C -> 2 K2CO3 + 3 K2SO4 + 6 CO2 + 5 N2}$$


There are plenty of questions in chem.SE related to gunpowder:


1. [What is the oxidation mechanism of gunpowder?](https://chemistry.stackexchange.com/questions/35680/what-is-the-oxidation-mechanism-of-gunpowder)
2. [What causes KNO3 to decompose into KNO2 and Oxygen in gunpowder?](https://chemistry.stackexchange.com/questions/70734/what-causes-kno3-to-decompose-into-kno2-and-oxygen-in-gunpowder)
3. [Why can sulfur act like a catalyst?](https://chemistry.stackexchange.com/questions/4173/why-can-sulfur-act-like-a-catalyst)
4. [How to write the balanced equation of the reaction of potassium nitrate, carbon, and sulfur?](https://chemistry.stackexchange.com/questions/37684/write-the-chemical-equation-of-this-reaction/37686#37686)
5. [What are the reaction products of sulfur and potassium nitrate?](https://chemistry.stackexchange.com/questions/42800/what-are-the-reaction-products-of-sulfur-and-potassium-nitrate)


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