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MolSynapse / Question bank / p-Block Elements: Groups 13 and 14 / Boron compounds: diborane, boric acid, borax, boron halides

JEE Main levelSingle correct optionDifficulty 2 of 3pb170

$BCl X_{3}$ is hydrolysed rapidly by water whereas $CCl X_{4}$ is not, because

A $B - Cl$ bond is weaker than $C - Cl$ bond only because boron is larger
Bboron in $BCl X_{3}$ has a vacant $2 p$ orbital that accepts a lone pair from water, while carbon in $CCl X_{4}$ has no vacant low-energy orbital
C $BCl X_{3}$ is a non-polar molecule so it mixes with water
D $CCl X_{4}$ is ionic and therefore insoluble in water

Answer: B

Water attacks boron through its lone pair into the empty

2 p

orbital of

BCl X_{3}

, starting hydrolysis to

B (OH) X_{3} + 3 HCl

. Carbon in

CCl X_{4}

has a filled octet and no available vacant orbital, so water cannot attack, and

CCl X_{4}

is inert to hydrolysis.

Practice p-Block Elements: Groups 13 and 14 More on Boron compounds: diborane, boric acid, borax, boron halides

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