Question

Give chemical equations to show the reaction between:
(i) Borax with ethanol in the presence of conc. H2SO4.
(ii) Diborane and chlorine
(iii) Diborane and caustic potash
(iv) Magnesium boride and phosphoric acid

Answer 1

(i) When borax is heated in sulphuric acid to yield boric acid. The mixture of boric acid and ethyl alcohol is heated to give triethyl borate.

$Na_{2}B_{4}O_{7}+H_{2}SO_{4}+5H_{2}O$ → $Na_{2}SO_{4}+H_{3}BO_{3}$

$H_{3}BO_{3}+C_{2}H_{5}OH$ → $B(OC_{2}H_{5})_{3}+3H_{2}O$

(ii) Diborane is a vigorously acting compound and gives boron trichloride on direct chlorination which is industrially used.

$B_{2}H_{6}+Cl_{2}$ → $B_{2}H_{5}Cl+HCl$

(iii) Diborane reacts with potassium hydroxide to produce potassium metaborate and hydrogen gas.

$B_{2}H_{6}+2KOH$ → $2KBO_{2}+6H_{2}$

(iv) Magnesium boride reacts with phosphoric acid with hydrogen gas to produce magnesium phosphate with diborane.

$3MgB_{2}+H_{3}PO_{4}+7H_{2}$ → $Mg_{3}(PO_{4})_{2}+3B_{2}H_{6}$