$A$ nonmetallic element of group $13$,used in making bulletproof vests,is an extremely hard solid of black colour. It can exist in many allotropic forms and has an unusually high melting point. Its trifluoride acts as a Lewis acid towards ammonia. The element exhibits a maximum covalence of four. Identify the element and write the reaction of its trifluoride with ammonia. Explain why the trifluoride acts as a Lewis acid.

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Solution

(N/A) The element is Boron $(B)$.
Reaction: $BF_3 + NH_3 \rightarrow F_3B \leftarrow NH_3$
Explanation: In $BF_3$,the boron atom has only $6$ electrons in its valence shell (incomplete octet). Therefore,it is electron-deficient and acts as a Lewis acid by accepting a lone pair of electrons from the Lewis base,ammonia $(NH_3)$.

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Class 11 Questions

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p-Block Elements (Class 11)

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Boron family

When borax is heated with $CoO$ on a platinum loop,the blue coloured bead formed is largely due to

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The reason for the polymeric nature of boric acid is .....

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Which of the following compounds is formed in the borax bead test?

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Match the following reactions in Column-$1$ with their main products in Column-$2$.

Column-$1$ (Reaction) Column-$2$ (Main product)

$A$. $B_2H_6 + 2CO \longrightarrow$ $I$. $B_2O_3$

$B$. $B_2H_6 + 3O_2 \longrightarrow$ $II$. $2BH_3 \cdot CO$

$C$. $B_2H_6 + 6H_2O \longrightarrow$ $III$. $2H_3BO_3$

The correct match is:

Column-$1$ (Reaction)	Column-$2$ (Main product)
$A$. $B_2H_6 + 2CO \longrightarrow$	$I$. $B_2O_3$
$B$. $B_2H_6 + 3O_2 \longrightarrow$	$II$. $2BH_3 \cdot CO$
$C$. $B_2H_6 + 6H_2O \longrightarrow$	$III$. $2H_3BO_3$