Q.(i) Give one example to show Boron acts as a powerful reducing agent. [2 marks]

(i) Boron reduces steam to hydrogen gas at red heat, showing its reducing power. (ii) Amorphous boron is obtained from borax via boric acid and boric oxide, finally reduced by magnesium.

This question offers an OR alternative (osmotic pressure by the Berkeley-Hartley method); the primary two-part Boron question is answered here in full.

(i) Boron as a powerful reducing agent [2 marks]:

Boron, when heated to redness (red-hot), can reduce steam (water vapour) to hydrogen gas, itself being oxidised to boric oxide:

2B + 3H2O(steam) --(red heat)--> B2O3 + 3H2

This reaction demonstrates boron's strong affinity for oxygen and its ability to act as a powerful reducing agent even towards a stable compound like water.

(ii) Isolation of boron from borax [3 marks]:

Borax, Na2B4O7.10H2O, is the principal ore from which boron is isolated, through the following steps:

Step 1 - Borax is dissolved and treated with concentrated hydrochloric acid, which precipitates boric acid:

Na2B4O7 + 2HCl + 5H2O -> 2NaCl + 4H3BO3

Step 2 - The boric acid obtained is filtered, dried, and then strongly heated (ignited) to drive off water and convert it to boric oxide (boron trioxide):

2H3BO3 --(heat)--> B2O3 + 3H2O

Step 3 - Boric oxide is then reduced with a reactive metal, usually magnesium powder, by strongly heating the mixture (a thermite-type reaction): …