Question

Borax is actually made of two tetrahedra and two triangular units joined together and should be written as : $N{a}_2\left[B_4{O}_5\right(OH{)}_4].8H_{2}O$
Consider the following statement about borax:
a. Each boron atom has four $B-O$ bond
b. Each boron atom has three $B-O$ bonds
c. Two boron atoms have four $B-O$ bonds while other two have three $B-O$ bonds
d. Each boron atom has one $-OH$ groups
Select correct statement(s):

• A. a, b
• B. b, c
• C. c, d
• D. a, c

Answer 1

The correct option is C c, d

Borax contains boron in both planar BO3 and tetrahedral BO4 units. It contains five B-O-B linkages.
The structure of borax is given below,

From the structure we can conclude that two boron atoms have four $B-O$ bonds and another two boron has three $B-O$ bonds.
Also each boron atom has one $-OH$ group.