What is the coefficient for ${\mathrm{OH}}^{-}$ after the equation

$-{\mathrm{Br}}_2+\dots {\mathrm{OH}}^{-}⟶\dots {\mathrm{Br}}^{-}+\dots {\mathrm{BrO}}_3^{-}+\dots {\mathrm{H}}_2\mathrm{O}$

is balanced with the smallest intezer coefficients?

When the reaction is balanced with smallest integer then it can be given as,

$3{\mathrm{Br}}_2+6{\mathrm{OH}}^{-}⟶5{\mathrm{Br}}^{-}+{\mathrm{BrO}}_3^{-}+3{\mathrm{H}}_2\mathrm{O}$

Here, coefficient of ${\mathrm{OH}}^{-}$ion is 6.