Preidict what will happern if molecular bromine `(Br_(2))` is added to a solution containing `NaCl` and `NaI` at `25^(@)C`. Assume all species are in their standard states.

Options

A. `Cl_(2)(g)` is realeased
B. `I_(2)(s)` is obtained
C. Both `Cl_(2)` and `I_(2)` are obtained
D. Neither `Cl_(2)` nor `I_(2)` is obtained

Answer

B

Explanation

To predict what redox reactions will take place, we need to compare the standard reduction potential for the following half reactions:
`{:(I_(2)(s)+2e^(-)hArr2I^(-)(aq., 1M)E^(@)=0.53V),(Br_(2)(l)+2e^(-)hArr2Br^(-)(aq., 1M)E^(@)=1.07 V),(Cl_(2)(g,1 "bar")+2e^(-)hArr 2Cl^(-)(aq.,1M)E^(@)=1.36V):}`
Since `E_(Br_(2)//Br^(-))^(@)gtE_(I_(2)//I^(-))^(@),Br_(2)` gets reduced by `I^9-)` i.e. `Br_(2)` will oxidized `I^(-)`. Since `E_(Br_(2)//Br^(-))^(@)gtE_(I_(2)//I^(-))^(@)`, `Br_(2)` will not oxidize `Cl^(-)`. Therefore, the only redox reaction that will occur appreciably under standard state conditions is
`{:("Oxidation"2I^(-)(aq.,1M)hArrI_(2)(s)+2e^(-)),("Reduction" Br_(2)(l)+2e^(-)hArr 2Br^(-)(aq.,1M)),(bar("Overall" 2I^(-)(aq.,1M)+Br_(2)(l)hArr I_(2)(s)+2Br(aq., 1M))):}`
Note that the `Na^(+)` ions are inert and do not enter into the redox reaction.