Reduction of borontrihalides: Reduction of borontrichloride with a metal assisted by dihydrogen gives metal borides. 2BCl + 2W K 2WB + 2Cl +2HCl H Formation of hydrides: Boron does not react directly with hydrogen. However, it forms a variety of hydrides called boranes. The simplest borane is diborane - B H .
Other larger boranes can be prepared from diborane. Treatment of gaseous boron trifluoride with sodium hydride around K gives diborane. To prevent subsequent pyrolysis, the product diborane is trapped immediately. 2BF + 6NaH K B H + 6NaF Formation of boron trihalides: Boron combines with halogen to form boron trihalides at high temperatures.
- - - - 2B + 3X Δ 2BX Formation of boron nitride: Boron burns with dinitrogen at high temperatures to form boron nitride. 2B + N Δ 2BN Formation of oxides: When boron is heated with oxygen around K, it forms its oxide. 4B + 3O 2B O K Reaction with acids and alkali: Halo acids have no reaction with boron. However, boron reacts with oxidising acids such as sulphuric acid and nitric acids and forms boric acid.
2B + 3H SO 2H BO + 3SO B + 3HNO H BO + 3NO Boron reacts with fused sodium hydroxide and forms sodium borate. 2B + 6NaOH 2Na BO + 3H Uses of boron: . Boron has the capacity to absorb neutrons. Hence, its isotope B is used as moderator in nuclear reactors.
. Amorphous boron is used as a rocket fuel igniter. . Boron is essential for the cell walls of plants.
. Compounds of boron have many applications. For example eye drops, antiseptics, washing powders etc.. contains boric acid and borax.
In the manufacture of Pyrex glass , boric oxide is used. . . .
Borax [Na B O .10H O]: Preparation: Borax is a sodium salt of tetraboric acid. It is obtained