Balance the redox reaction by inserting the appropriate coefficients

Question

Balance the redox reaction by inserting the appropriate coefficients

redox reaction: H₂O+Se_Cd²⁺--->Cd+SeO₃^2-+H⁺

Answer 1

Se(s) + 3Cd²⁺(aq) + 3H₂O ==> 3Cd(s) + SeO₃(aq) + 6H⁺(aq) ... Overall balanced equation

Oxidation half reaction:

Se(s) ==> SeO₃(aq)

Se(s) + 3H₂O ==> SeO₃(aq) ... balanced for Se and O

Se(s) + 3H₂O ==> SeO₃(aq) + 6H⁺ ... balanced for Se and O and H

Se(s) + 3H₂O ==> SeO₃(aq) + 6H⁺ + 6e- ... balanced for Se, O, H, and charge = BALANCED EQ.

Reduction half reaction:

Cd²⁺(aq) ==> Cd(s)

Cd²⁺(aq) + 2e- ==> Cd(s) ... balanced for Cd and charge = BALANCE EQ.

Multiply by 3 to equalize electrons with oxidation half reaction to get...

3Cd²⁺(aq) + 6e- ==> 3Cd(s)

Add oxidation and reduction half reactions:

Se(s) + 3H₂O ==> SeO₃(aq) + 6H⁺ + 6e-

3Cd²⁺(aq) + 6e- ==> 3Cd(s)

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Se(s) + 3Cd²⁺(aq) + 3H₂O(l) ==> SeO₃(aq) + 3Cd(s) + 6H⁺(aq) BALANCED REDOX EQUATION