1. In diamond, all the carbon atoms are in sp3 hybridised state. Due to this closely packed arrangement, it is hard. Since, there are no free electrons it is an insulator. But in graphite, the carbon atoms are in sp2 hybridised state. It is a good conductor due to the presence of delocalised electrons between the layers. Graphite cleaves easily between the layers. Therefore, It is very soft and slippery.
2. On heating, orthoboric acid above 370 K forms metaboric acid, HBO2 which on further heating yields boric oxide, B2O3 .
3. B3N3H6 is called Inorganic benzene. It is obtained by heating diborane with ammonia.
