# Why is hydrated barium peroxide used in the preparation of hydrogen peroxide?

I read about the laboratory method of producing hydrogen peroxide. The chemical reaction in question is: $$\text{BaO}_2.8\text{H}_2\text{O} + \text{H}_2\text{SO}_4 \rightarrow \text{BaSO}_4+\text{H}_2\text{O}_2 + 8\text{H}_2\text{O}$$ I wanted to find out why the hydrated form of barium peroxide is used. Apparently, what made barium peroxide so attractive to use in this reaction was the fact that the product, barium sulphate, being insoluble, is easy to filter out after the reaction. However, the side effect is that it precipitates on the barium peroxide sample, preventing further reaction. Using the hydrated form of barium peroxide solves this problem as the salt molecule is "surrounded" by water molecules.

I don't understand exactly how this works. What does a hydrated $$\text{BaO}_2$$ molecule look like in space, and how does its geometry help avoid the problem of a precipitate forming on its surface?

• What book are these statements from? Sounds quite detailed. Mar 11 at 12:52
• I'm paraphrasing what I read and watched online. My high school textbook contains only the chemical reaction at the top of the question. Mar 11 at 12:54
• Both peroxides are nearly insoluble in water. Probably the eight water molecules from $\ce{BaO2·8H2O}$ help insoluble $\ce{BaSO4}$ produced by he reaction quit the surface of the grain, which allows new sulfuric acid to touch and react with the inner part of the grain of peroxide. If $\ce{BaO2}$ is not surrounded by water molecules, $\ce{BaO2}$ is simply replaced by $\ce{BaSO4}$ at the surface of the grain, which produce a protective layer of insoluble $\ce{BaSO4}$ and protects the inner part of the grain from further reaction with the sulfuric acid solution. Mar 11 at 14:23
• Thanks for your comment, that explanation sounds convincing. Although I think I understand what "grain" means in this context, I've never heard the term used before so I can't be sure. Could you explain what you mean by it please? Mar 11 at 14:27
• @Ray Bradbury I might have said a piece, or a bit, or a crystal, instead of a grain. Mar 11 at 14:56