p-Block Elements-I - Result Question 42
####13. The crystalline form of borax has
(2016 Adv.)
(a) tetranuclear $\left[B _4 O _5(OH) _4\right]^{2-}$ unit
(b) all boron atoms in the same plane
(c) equal number of $s p^{2}$ and $s p^{3}$ hybridised boron atoms
(d) one terminal hydroxide per boron atom
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Answer:
Correct Answer: 13. (b)
Solution:
- $Na _2 B _4 O _7 \cdot 10 H _2 O$ (borax) is actually made of two tetrahedral and two triangular units, and is actually written as $Na _2\left[B _4 O _5(OH) _4\right] \cdot 5 H _2 O$.
(a) Thus, correct.
(b) Boron atoms are in different planes thus, incorrect.
(c) Two $s p^{2}$ and two $s p^{3}$-hybridised B atoms thus, correct.
(d) Each boron has one - $OH$ group thus, correct.
