What happened when Diborane (B2H6) heated at 250 C
First I am not sure whether the temperature is 25oC or 250oCYour question does not specify whether Diborane is heated in a vacuum or in the air. However, I will try to answer it exhaustively.
If the temperature is 25oC and there is air present: Diborane will auto-ignite spontaneously in air and burn to form boron trioxide and water.
2B2H6 + 6O2 2B2O3 + 6H2O
The remaining can also react violently with the water produced to give boric acid and hydrogen.
If the temperature is 25oC and there is no air, diborane will decompose slowly into hydrogen and higher boranes. Decomposition is accelerated at higher temperatures.
If the temperature is 2500C, diborane will decompose to boron and hydrogen.