Question

Write balanced net ionic equations for the following reactions in basic solution? I'm having trouble with these basic solution half reaction problems, any help would be great.

S2O32−(aq)+I2(aq)→S4O62−(aq)+I−(aq)

Answer 1

Well, let us see....we write the individual redox reactions.....

Explanation:

`"Reduction...."`

`1/2I_2 + e^(-) rarr I^-` `(i)`

`"Oxidation...."`

`2S_2O_3^(2-) rarr S_4O_6^(2-)+ 2e^(-)` `(ii)`
i.e. `S(+II)rarrS(+II*1/2)`

Note that in `"tetrathionite ion"` we gots individual oxidation states of `(""^(-)O-)stackrel(+V)S(=O)_2-stackrel(0)S-stackrel(0)S-(O=)_2stackrel(+V)S-O^(-)`, and I took the AVERAGE oxidation state....`(""^+V+0+0+V^+)/4=+II*1/2`.

And so we take...`2xx(i)+(ii)`

`I_2 + 2S_2O_3^(2-)+cancel(2e^(-)) rarr S_4O_6^(2-)+ cancel(2e^(-)) +2I^-`

And certainly this is balanced with respect to mass and charge. And neither hydronium ion nor hydroxide ion is involved in the redox transfer...so we can reasonably ignore `pH`....