Galvanic cells: H+ vs H2SO4, and Br2(aq) vs Br2(l)

[i_love_science]

For the reaction 12H+ + 2 IO(3-) + 10 Fe(2+) - > I2 + 6 H2O + 10 Fe(3+), the solution says that H2SO4(aq) is in the cathode. For the reaction 2 H2O2 - > O2 + 2 H2O, the solution says that H+(aq) is in the cathode and anode. When is H2SO4(aq) or H+(aq) more appropriate in the galvanic cell description?

Also, why is Br2(aq) in galvanic cells rather than Br2(l)?

Thanks.

 

[snorkack]

Also, why is Br2(aq) in galvanic cells rather than Br2(l)?

Not sure why H₂SO₄(aq) rather than H⁺(aq).
Br₂(aq) has electrode potential that depends on its concentration in solution. In saturated solution in equilibrium with Br₂(l), the concentration of Br₂(aq) is fixed by solubility and potential should be the same for Br₂(aq) as for Br₂(l).

 

[Mayhem]

H₂SO₄ acts very much as a proton donor in redox chemistry and the redox properties of its deprotonated forms can often be neglected AFAIK.