Boric acid is solid, whereas $\mathrm{BF}_{3}$ is gas at room temperature because of

(C) Strong hydrogen bond in Boric acid

(A) Strong ionic bond in Boric acid

(B) Strong van der Waal's interaction in Boric acid

(D) Strong covalent bond in $\mathrm{BF}_{3}$

JEE Main · 2023 · 30 Jan 2023 · Shift 2 · Chemical Bonding and Molecular Structure

Boric acid is solid, whereas

BF_{3}

is gas at room temperature because of

(A)Strong ionic bond in Boric acid
(B)Strong van der Waal's interaction in Boric acid
(C)Strong hydrogen bond in Boric acid✓ Correct
(D)Strong covalent bond in $BF_{3}$

Answer: (C)

Solution

The difference in physical state comes from the forces between the molecules. In boric acid each

B (OH)_{3}

unit is linked to its neighbours through an extended network of hydrogen bonds, building a layered solid that holds together well above room temperature. Boron trifluoride has no such hydrogen bonding; its planar molecules attract one another only through weak van der Waals forces, so it stays a gas. The solid state of boric acid is due to the strong hydrogen bonding within it.

JEE Main · 2023 · 30 Jan 2023 · Shift 2 · Single correct option

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JEE Main · 2023 · 30 Jan 2023 · Shift 2 · Chemical Bonding and Molecular Structure

Solution

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