Ncert Exercises & Solutions

What happens when

(a)Borax is heated strongly,

(b)Boric acid is added to water,

(d) $B F_{3}$ is reacted with ammonia?

(a) When heated, borax undergoes various transitions. It first loses water molecules and swells. Then, it turns into a transparent liquid, solidifying to form a glass-like material called borax bead.

N a_{2} B_{4} O_{2} . 10 H_{2} O \overset{∆}{\to} N a_{2} B_{4} O_{7} \overset{∆}{\to} 2 N a B O_{2} + B_{2} O_{3}

B o r a x S o d i u m m e t a b o r a t e B o r i c a n h y d r i d e

(b) When boric acid is added to water, it accepts electrons from

{}_{-}O

H ion.

B {(O H)}_{3} + 2 H O H \to [B {(O H)}_{4}]^{-} + H_{3} O^{+}

2 A I_{(s)} + 2 N a O H_{(a q)} + 6 H_{2} O_{(l)} \to 2 N a^{+} [A I (O H

₄)]-(aq)+3H2(g)

(d)

B F_{3}

(a Lewis acid) reacts with

N H_{3}

(a Lewis base) to form an adduct. This results in a
complete octet around B in

B F_{3}

F_{3} B + : N H_{3} \to F_{3} B \leftarrow : N H_{3}

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