Balance these reactions and please show how you did it: a) CH4 + NO2 → N2 + CO2 + H2O (b) Zn + Cr2O72- + H+ → Zn2+ + Cr3+ + H2O?

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  • 2 years ago
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    CH4 + 2NO2 = N2 + CO2 + 2H2O


    First write down the two half equations.

    Notice (1) we insert electrons to balance the two half equations

    (2) We make up 'water' ion the RHS to balance all the oxygens in the dichromate

    (3) We then 'back' balance 'H^+' to balance all the hydrogens in water.

    (4) We then balance the charges by putting in electrons on the LHS.

    Zn = Zn^2+ + 2e^-

    Cr2O7^2- + 14H^+ + 6e^- = 2Cr^3+ + 7H2O

    We now multiply the two half equations to balance the number of electrons in each equation.


    3Zn = 3Zn^2+ + 6e^-

    Cr2O7^2- + 14H^+ + 6e^- = 2Cr^3+ + 7H2O

    Add the two half equations, this will remove the electrons .


    3Zn + Cr2O7^2- + 14H^+ = 3Zn^2+ + 2Cr^3+ + 7H2O


    Hope that helps!!!!

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