1 write the reactants and products for the reaction

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Unformatted text preview: e3+ by Cr2O72- in an acidic solution? 1. Write the reactants and products for the reaction in ionic form Fe2+ + Cr2O72- Fe3+ + Cr3+ 2. Separate the equation into two half-reactions half- Oxidation: +2 Fe2+ - +3 Fe3+ +6 Reduction: +3 Cr2O72- Cr3+ Balancing Redox Equations 3. Balance each half-reaction halfa. Balance the atoms other than O and H in each half-reaction the halfCr2O72- 2Cr3+ atoms atoms b. add H2O to balance O atoms and H+ to balance H atoms in acidic soln (add OH- to balance O atoms and H2O to in acidic atoms balance atoms in basic balance H atoms in basic soln) Cr2O72- 2Cr3+ + 7H2O 2Cr3+ + 7H2O 14H+ + Cr2O72Cr c. Add electrons to one side of each half-reaction to balance the electrons halfbalance charges on the half-reaction half6e- + 14H+ + Cr2O72Cr Fe2+ 2Cr3+ + 7H2O Fe3+ + 1e- Balancing Redox Equations 4. Equalize the number of electrons in the two half-reactions by multiplying the half-reactions by appropriate coefficients. 6e- + 14H+ + Cr2O72Cr 6Fe2+ 2Cr3+ + 7H2O 6Fe3+ + 6e- 5. Add the two half-reactions together and balance the final equation halfOxidation: Reduction: 6Fe2+ 6e- + 14H+ + Cr2O72Cr 14H+ + Cr2O72- + 6Fe2+ 6Fe3+ + 6e2Cr3+ + 7H2O 6Fe3+ + 2Cr3+ + 7H2O 6. Verify that the number of atoms and the charges are balanced. 14H+ + Cr2O72- + 6Fe2+ = 6Fe3+ + 2Cr3+ + 7H2O Example Example - In a qualitative cation analysis lab, a student added solid sodium sodium bismuthate (NaBiO3) to a Mn2+ (aq) in an acidic s...
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