JEE Main On 16 April 2018 Question 16
Question: A group 13 element X reacts with chlorine gas to produce a compound $ XCl _3.XCl _3 $ is electron deficient and easily reacts with $ NH _3 $ to form $ Cl _3X\to NH _3 $ adduct; however, $ XCl _3 $ does not dimerize. X is: [JEE Main 16-4-2018]
Options:
A) B
B) Al
C) Ga
D) In
Show Answer
Answer:
Correct Answer: A
Solution:
- The required 13 group element is Boron. When it reacts with chlorine then it form $ BCl _3 $ The reaction is as follow: $ 2B+3Cl _2\to 2BCl _3 $ When it reacts with $ NH _3 $ then it forms adduct which can be represented as $ BCl _3arrow NH _3 $ and with excess of ammonia it forms boron nitride. $ BCl _3+4NH _3\to BN+3NH _4Cl $ $ BCl _3 $ is electron deficient group but it does not form dimer like Al, Ga or In because its electron deficiency is complemented by the formation of co-ordinate bond between lone pair of electron of chlorine and empty unhybridized p-orbital of boron forming $ p\pi -p\pi $ bonding.
