Write the balanced reaction where thiosulfate and protons are the only reactants; and water, elemental sulfur, sulfur trioxide, and water are the only products. (Hint: this easier if you start with the balanced half-reactions). How many electrons are transferred in the balanced oxidation half reaction? How many electrons are transferred in the balanced reduction half reaction? How many electrons are transferred in the overall reaction? Solution S2O3^2- (aq) + H^+ -------------> S + SO3 + H2O Oxidation half reaction                                                                                reduction half reaction S2O3^2- (aq) ------------> 2SO3(g)                                                            S2O3^2- ------------> 2S S2O3^2- (aq)+3H2O ------------> 2SO3(g)                                          S2O3^2- ------------> 2S+ 3H2O S2O3^2- (aq)+3H2O ------------> 2SO3(g)+ 6H^+(aq)                       S2O3^2- + 6H^+ (aq) ------------> 2S+ 3H2O S2O3^2- (aq)+3H2O ------------> 2SO3(g)+ 6H^+(aq) + 8e^-          S2O3^2- + 6H^+ (aq) +4e^- ------------> 2S+ 3H2O S2O3^2- (aq)+3H2O ------------> 2SO3(g)+ 6H^+(aq) + 8e^-         ( 8 electrons are transferred) 2S2O3^2- + 12H^+ (aq) +8e^- ------------> 4S+ 6H2O                     ( 8 electrons are transferred) ------------------------------------------------------------------------------------------------------ 3S2O3^2- (aq) +6H^+ (aq) --------------> 2So3(g) + 4S +3H2O overall reaction .

1. Write the balanced reaction where thiosulfate and protons are the only reactants; and water,
elemental sulfur, sulfur trioxide, and water are the only products. (Hint: this easier if you start
with the balanced half-reactions). How many electrons are transferred in the balanced oxidation
half reaction? How many electrons are transferred in the balanced reduction half reaction? How
many electrons are transferred in the overall reaction?
Solution
S2O3^2- (aq) + H^+ -------------> S + SO3 + H2O
Oxidation half
reaction                                    Â
                                       Â
  reduction half reaction
S2O3^2- (aq) ------------>
2SO3(g)Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                       S2O3^2- ------------> 2S
S2O3^2- (aq)+3H2O ------------>
2SO3(g)Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
     S2O3^2- ------------> 2S+ 3H2O
S2O3^2- (aq)+3H2O ------------> 2SO3(g)+ 6H^+(aq)
                     S2O3^2- + 6H^+ (aq) ------------> 2S+ 3H2O
S2O3^2- (aq)+3H2O ------------> 2SO3(g)+ 6H^+(aq) + 8e^- Â Â Â Â Â Â Â Â S2O3^2- +
6H^+ (aq) +4e^- ------------> 2S+ 3H2O
S2O3^2- (aq)+3H2O ------------> 2SO3(g)+ 6H^+(aq) + 8e^- Â Â Â Â Â Â Â ( 8 electrons are
transferred)
2S2O3^2- + 12H^+ (aq) +8e^- ------------> 4S+
6H2OÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ( 8 electrons are transferred)
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2. 3S2O3^2- (aq) +6H^+ (aq) --------------> 2So3(g) + 4S +3H2O overall reaction