Q.Describe the structure of boron oxide, $\text{B}_2\text{O}_3$, and explain how it is related to boric acid on heating. Give the sequence of dehydration from orthoboric acid to metaboric acid to boron oxide.

[!TLDR] B2O3 is a covalent network of planar BO3 triangular units linked by bridging oxygens; heating boric acid drives off water stepwise, first to metaboric acid (HBO2) then to B2O3. [!ANSWER] $\text{B}_2\text{O}_3$ is built from $sp^2$, planar $\text{BO}_3$ triangles linked through shared bridging oxygens into a glass-forming network; heating bo …

Boron oxide, $\text{B}_2\text{O}_3$, is a covalent network solid built from planar, $sp^2$-hybridised $\text{BO}_3$ triangular units — each boron three-coordinate, bonded to three oxygen atoms in a plane — linked together through shared, bridging oxygen atoms into an extended, disordered (glass-forming) network; this network structure is exactly why $\text{B}_2\text{O}_3$ is the key glass-forming component of borosilicate glass. $\text{B}_2\text{O}_3$ is directly related to boric acid by a stepwise thermal dehydration sequence. On first heating, orthoboric acid $\text{B(OH)}_3$ loses a molecule of water to form metaboric acid, $\text{HBO}_2$:\n$\text{B(OH)}_3 \xrightarrow{\Delta} \text{HBO}_2 + \text{H}_2\text{O}$\nOn further, stronger heating, metaboric acid loses a further water molecule (across two $\text{HBO}_2$ units) to leave boron oxide itself:\n$2\text{HBO}_2 \xrightarrow{\Delta} \text{B}_2\text{O}_3 + \text{H}_2\text{O}$\nSo the full dehydration sequence runs orthoboric acid $ …

Describe B2O3's triangular BO3 network structure, then give the two-step thermal dehydration sequence from bo …

Describing B2O3's boron centres as tetrahedral rather than the correct planar triangular (BO3) geometry; omitting the intermediate metaboric acid sta …