p-Block Elements-I 2 Question 26
26. (i) How is boron obtained from borax? Give chemical equations with reaction conditions.
(ii) Write the structure of $\mathrm{B}{2} \mathrm{H}{6}$ and its reaction with $\mathrm{HCl}$.
(2002)
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Solution:
(i) $3 \mathrm{SiCl}{4}+4 \mathrm{Al} \stackrel{\Delta}{\longrightarrow} 3 \mathrm{Si}+4 \mathrm{AlCl}{3}$;
$\mathrm{Mg}$ or $\mathrm{Zn}$ can also be used.
(ii) $\mathrm{SiCl}{4}+2 \mathrm{CH}{3} \mathrm{MgCl} \longrightarrow\left(\mathrm{CH}{3}\right){2} \mathrm{SiCl}{2}+2 \mathrm{MgCl}{2}$
(iii) $\mathrm{SiCl}{4}+4 \mathrm{H}{2} \mathrm{O} \longrightarrow \underset{\text { Unstable }}{\mathrm{Si}(\mathrm{OH})_{4}}+4 \mathrm{HCl}$
$$ \mathrm{Si}(\mathrm{OH}){4} \xrightarrow{\text { heat }} \mathrm{SiO}{2}+2 \mathrm{H}_{2} \mathrm{O} $$
$\mathrm{SiO}{2}+\mathrm{Na}{2} \mathrm{CO}{3} \stackrel{\Delta}{\longrightarrow} \mathrm{Na}{2} \mathrm{SiO}{3}+\mathrm{CO}{2}$
