B(OH)_3+NaOH leftharpoons NaBO_2+Na[B(OH)_4]+H_2 O . How can this...

This reaction is reversible reaction because sodium metaborate, $\mathrm{Na}^{+}$\left[\mathrm{B}(\mathrm{OH})_4\right]^{-}$formed by the reaction between$\mathrm{B}(\mathrm{OH})_3$and$\mathrm{NaOH}$gets hydrolysed to regenerate$\mathrm{B}(\mathrm{OH})_3$and$\mathrm{NaOH}$<img src="https://cdn-question-pool.Quantrex.app/pyq/jee_advanced/HTQ4_yy4c1xOjkvE_9BMrxfhp7VKkCLr5fdyJ0Wx66E.original.fullsize.png"><br> If, some quantity of polyhydroxy compound like cis-1, 3-diol, catechol, glycerol etc. is added to the reaction mixture. The$\mathrm{B}(\mathrm{OH})_3 combines with such polyhydroxy compound to give chelated complex compound. Due to complex compound formation, stability increases and due to higher stability of complex, reaction moves in forward direction.