1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Balance Half-Cell Equation

  1. Jul 5, 2006 #1
    Ok, here is another one I have, this is one of a series of half-cell questions... this one is confusing.

    79. Balance the following equations by the half-cell method. Show both half-cell reactions and identify them as oxidation or reduction.
    b) Cl2(g) + OH- <=> Cl- + ClO3^- + H2O(l)

    Oxidation Reaction:
    Cl2 (g) <-> Cl-
    2e- + Cl2 <-> 2Cl- --- Balanced Cl molecules and electrons

    Reduction Reaction:
    Cl2 (g) <-> ClO3-
    Cl2 + 6H2O <-> 2ClO3- + 12H+ 10e-

    Multiply the oxidation reaction by a factor of 5 to cross out the e-
    5Cl2 <-> 10Cl-

    Add them together:
    6Cl2 + 6H2O <-> 10Cl- + 2ClO3- + 12H+

    Since this is a basic solution we must swap out the H+ with OH-... in this case adding 6OH- to each side

    6Cl2 + 6H2O + 12OH- <-> 10Cl- + 2ClO3- + 12HOH

    This seems kinda insane but it may just be right.
    Can anyone give me some input on this?
  2. jcsd
  3. Jul 5, 2006 #2
    Ha, I was just reviewing these today.
    You can cancel out the H2O since you have it on both sides.

    6Cl2 + 12OH- --> 10Cl- + 2ClO3- + 6H2O

    You can divide all of the coefficients by 2. It seems that sometimes when you work with diatomic molecules like Cl2 that your final answer will be doubled. I made the same mistake here: https://www.physicsforums.com/showthread.php?t=96870

    3Cl2 + 6OH- --> 5Cl- + ClO3- + 3H2O

    Copy and paste that line into google and the results show that you're good :smile: .
    Last edited: Jul 5, 2006
  4. Jul 5, 2006 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    This thread is a double-post. The other copy is in Chemistry.

    Yellowduck - please do not post multiple copies of the same thing!
  5. Jul 6, 2006 #4


    User Avatar

    Staff: Mentor

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook