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JEE Main levelSingle correct optionDifficulty 2 of 3sb022

Which equation correctly represents the preparation of lithium aluminium hydride (in dry ether)?

A $3 LiH + AlCl X_{3} LiAlH X_{4} + 2 LiCl$
B $4 LiH + AlCl X_{3} LiAlH X_{4} + 3 LiCl$
C $LiH + AlCl X_{3} LiAlH X_{4} + LiCl$
D $2 LiH + AlCl X_{3} LiAlH X_{4} + 2 LiCl$

Answer: B

Balance Al: 1 on each side. Four hydrogens are needed in

LiAlH X_{4}

, so 4

LiH

are needed, and the lithium count then gives

4 - 1 = 3

LiCl

, matching the 3 chlorines from

AlCl X_{3}

. Hence

4 LiH + AlCl X_{3} LiAlH X_{4} + 3 LiCl

.

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