The correct statements among (a) to (b) are: (a) saline hydrides produce \(\mathrm{H}_{2}\) gas when reacted with \(\mathrm{H}_{2} \mathrm{O}\). (b) reaction of \(\mathrm{LiAH}_{4}\) with \(\mathrm{BF}_{3}\) leads to \(\mathrm{B}_{2} \mathrm{H}_{6}\). (c) \(\mathrm{PH}_{3}\) and \(\mathrm{CH}_{4}\) are electron - rich and electron-precise hydrides, respectively. (d) HF and \(\mathrm{CH}_{4}\) are called as molecular hydrides.

JEE Main · 2019 · 10 Apr 2019 · Shift 2 · Hydrogen

The correct statements among (a) to (b) are:
(a) saline hydrides produce

H_{2}

gas when reacted with

H_{2} O

.
(b) reaction of

LiAH_{4}

with

BF_{3}

leads to

B_{2} H_{6}

.
(c)

PH_{3}

and

CH_{4}

are electron - rich and electron-precise hydrides, respectively.
(d) HF and

CH_{4}

are called as molecular hydrides.

(A)(c) and (d) only
(B)(a), (b) and (c) only
(C)(a), (b), (c) and (d)✓ Correct
(D)(a), (c) and (d) only

Answer: (C)

Solution

Each statement holds. Saline hydrides such as

NaH

liberate hydrogen with water,

NaH + H X_{2} O NaOH + H X_{2}

. Lithium aluminium hydride reacts with boron trifluoride to give diborane,

4 BF X_{3} + 3 LiAlH X_{4} 2 B X_{2} H X_{6} + 3 LiF + 3 AlF X_{3}

. Phosphine has a spare lone pair and is electron-rich, while methane has exactly the electrons it needs for bonding and is electron-precise. And both

HF

and

CH X_{4}

are covalent, molecular hydrides. So all four are correct.

JEE Main · 2019 · 10 Apr 2019 · Shift 2 · Single correct option

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JEE Main · 2019 · 10 Apr 2019 · Shift 2 · Hydrogen

Solution

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