Redox Question HELP!

[john216]

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HI,
this is question from qvault Chem.
Could you guys tell me steps in finding balanced equation of following:?

H2SO4 (aq) + NaBr (s) ⟶ Br2 (l) + SO2 (g) + Na2SO4 (aq) + H2O (l)

 

[starnova]

balance everything except H and O
2H2SO4 (aq) + 2NaBr (s) > Br2 (l) + SO2 (g) + Na2SO4 (aq) + H2O (l)
S(+6) >> S(+4) and S(+6) so only 1 S goes from +6 to +4 = 2 electrons gained
Br goes from -1 to 0 twice = 2 electrons lost
Since you gain 2/lose 2 electrons, you can just skip the equation multiplication step in half reaction method and go right to balancing H and O
2H2SO4 (aq) + 2NaBr (s) > Br2 (l) + SO2 (g) + Na2SO4 (aq) + 2H2O (l)

 

[john216]

thanks for the reply..
could you elaborate on
"S(+6) >> S(+4) and S(+6) so only 1 S goes from +6 to +4 = 2 electrons gained"

I get oxidation state for S on the left side (2H2SO4) is + 6.
And the right side SO2 and Na2SO4, with oxidation state of +4 and + 6.
Since its +6 on left and +10 (total) on right, isn't it losing 4 e-?

 

[starnova]

well, you've 2 S on the left side
one S (+6) goes to S (+6) from Na2SO4 on your right
another S (+6) goes to S (+4) from SO2
so it's only 2 electrons, be careful about this

 

[starnova]

that's why the FIRST step is to balance everything except H and O