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Homework Help: Redox reacions equations

  1. Aug 4, 2008 #1
    hey i'm in yr 12 chemistry in Australia and im having problems understanding redox reactions equations, i understand oxidation states and a little bit but i cant figure our about the electrons calculus, i can do the rest of the formula or steps but i cannot seem to be able to calculate the electron transfer accurately i was hoping some one would be able to help with methods or something.
    thank you
  2. jcsd
  3. Aug 5, 2008 #2


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    Staff: Mentor

  4. Aug 10, 2008 #3
    thanks but that doesn't really help me calculate how to balance electrons in half equations (thats the only problem i am having)
  5. Aug 10, 2008 #4
    I think I understand what you are having trouble with. When you are finished balancing a half-equation and lets say it looks like this:
    Au3+(aq) + 2I−(aq) -> Au(s) + I2(s)
    (3+ and - on left side are charges), so you have Au (3+) and I (2-) on left, and on right you dont have any charges as you can see. Notice that when you have a number in front like 2I, make sure you dont forget that number and see only one (-) at the top, you actually have (2-). So, now 2 out of 3 protons of Au on left will balance 2 electrons on left and you will be left with one proton (1+) on left. Then, if you want to balance electrons, you see that you have zero on right and you want same on left so you add one e- to the left to cancell the proton (+) you had left over after you balanced your equation. Same thing if you had in the end 4+ on left and 2- on right of equation you would add 6- to left to cancell 4+ and have 2- left over to balance the right side.

    Hope this helps
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