I’m really having a hard time identifying which species is being oxidized in the
ID: 635740 • Letter: I
Question
I’m really having a hard time identifying which species is being oxidized in the Hg equation the very first oneWhen writing cell notation is it required that the half reactions or the species in the cell notations are balance and if I do choose to balance the species will it be wrong too?
Thank you s 19.65 Consider the following reactions. Are they sponta- neous in the direction written, under standard conditions D Hg22+(aq) + 2Fe3+(aq)-? 2Hg?"(aq) + 3Fe2+(aq) 4SO4(a+O2(8) +4H (a) I)at 25°C? D 25,082-(aq) +2H20(1) n-
Explanation / Answer
a) As it is oxidised the first reaction involving mercury species is found to be oxidised,It's oxidation state is changed from +1 state to +2 state.
SPONTANEOUS OR NOT ----BUT TO NOTE THAT THIS REACTION CANNOT BE SPONTANEOUS., SINCE IRON IS MORE ACTIVE IN ELECT5ROCHEMICAL SERIES AS BETTER REDUCING AGENT THAN MERCURY AND SO IRON REDUCES MERCURY ION TO MERCURY METAL AND GET ITSELF(IRON) OXIDISED.
B) This reaction is feasible.
2S2O8-2 +4e- -------------------->4 SO4-2 . This half reaction having positive potential value of 2v
O2 + 4H+ +4e- ---------------------> 2H2O, This half reaction having negative potential value of -1.23 v
Half reaction having - ve potential is oxidising and reduces the tetrathionate ion to sulphate ion.
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Balancing the half rreactions in writing cell notation is not required. Cell notation is to represent the anode half cell and cathode half.
Cell notation showing balancing of all species is not IUPAC NORMS.
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