question_answer

Calculate the millimoles of \[Se{{O}_{3}}^{2-}\]in solution on the basis of following data: 70 ml of \[\frac{M}{60}\]solution of \[KBr{{O}_{3}}\] was added to \[Se{{O}_{3}}^{2-}\]solution. The bromine evolved was removed by boiling and excess of \[KBr{{O}_{3}}\] was back titrated with 12.5 mL of \[\frac{M}{25}\]solution of \[NaAs{{O}_{2}}.\] The reactions are given below. [a] \[\text{SeO}_{\text{3}}^{\text{2-}}\text{+BrO}_{\text{3}}^{\text{-}}\text{+}{{\text{H}}^{\text{+}}}\to \text{SeO}_{\text{4}}^{\text{2-}}\text{+B}{{\text{r}}_{\text{2}}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\] [b] \[\text{BrO}_{\text{3}}^{\text{-}}\text{+AsO}_{\text{2}}^{\text{-}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\to \text{B}{{\text{r}}^{\text{-}}}\text{+AsO}_{\text{4}}^{\text{3-}}\text{+}{{\text{H}}^{\text{+}}}\]

A)  \[1.6\times {{10}^{-3}}\]                             

B)  125

C)  2.5                                        

D)  None of these