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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: zeoblade on February 25, 2010, 07:58:22 PM

Title: Balancing redox reactions
Post by: zeoblade on February 25, 2010, 07:58:22 PM

Would someone please check my working that I have double checked to find any mistakes I haven't picked up on?

I need to balance ionically these equations and have attempted so:

1) Pb²⁺(aq) + 2Cl^-(aq) --> PbCl₂(s)

2) Cu²⁺(aq) + H₂S(g) --> CuS(s) + 2H⁺(aq)

3) CO₃^2- + 2H⁺ --> CO₂(g) + H₂O(l)

4) 3Ba³⁺(aq) + 2PO₄^3- --> Ba₃(PO₄)₂

I need to balance these redox half equations and have attempted so:

5) H₂C₂O₄(?) --> CO₂(g) + 2H⁺(aq):
H₂C₂O₄(?) --> 2CO₂(g) + 2H⁺(aq) + 2e^- (I don't know the phase of H₂C₂O₄)

6) ClO₃^-(aq) + H⁺(aq) --> Cl₂(g) + H₂O(l)
2ClO₃^-(aq) + 12H⁺(aq) + 10e^- --> Cl₂(g) + 6H₂O(l)

I need to balance these full redox equations and have attempted so:

7) Fe(s) --> Fe²⁺(aq) with H⁺(aq) --> H₂(g)
Fe(s) --> Fe²⁺(aq) + 2e^-
2H⁺(aq) + 2e^- --> H₂(g)
Fe(s) + 2H⁺(aq) --> Fe²⁺(aq) + H₂(g) (transfer of 2e^-)

8.) MnO₄^-(aq) --> Mn²⁺(aq) with H₂O₂(l) --> O₂(g)
MnO₄^-(aq) + 8H⁺(aq) + 5e^- --> Mn²⁺(aq) + 4H₂O(l) x2
H₂O₂(l) --> O₂(g) + 2H⁺(aq) + 2e^- x5
2MnO₄^-(aq) + 6H⁺(aq) + 5H₂O₂(l) --> 2Mn²⁺(aq) + 8H₂O(l) + 5O₂(g) (transfer of 10e^-)