Identify the correct statements from the following a) Borax gives blue coloured Co ( BO ₂ )₂ when heated with Co ²⁺ salt. b) The correct formula of Borax is Na ₂ [ ~B ₄ O ₅( OH )₄ ] 8 H ₂ O c) Trihalides of boron are Lewis bases.

Step-by-step solution

- a) Borax gives blue colored ( Co ( BO ₂ )₂ ) when heated with ( Co ²⁺ ) salt. This is correct. This is a classic test for metal ions using the borax bead test. When borax is heated, it forms a glassy bead of sodium metaborate and boric anhydride. In the presence of a cobalt salt, cobalt metaborate, ( Co ( BO ₂ )₂ ), is formed, which gives a characteristic blue color. - b) The correct formula of Borax is ( Na ₂ [ ~B ₄ O ₅( OH )₄ ] 8 H ₂ O ). This is correct. This is the more accurate formula for borax (sodium tetr