Struggling with Redox Reaction Equations?

[koosney@stcc]

hey I'm in yr 12 chemistry in Australia and I am having problems understanding redox reactions equations, i understand oxidation states and a little bit but i can't 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

 

[Borek]

Check out this page:

http://www.chembuddy.com/?left=balancing-stoichiometry&right=oxidation-numbers-method

 

[koosney@stcc]

thanks but that doesn't really help me calculate how to balance electrons in half equations (thats the only problem i am having)

 

[jaska22]

Hi,
I think I understand what you are having trouble with. When you are finished balancing a half-equation and let's 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 don't have any charges as you can see. Notice that when you have a number in front like 2I, make sure you don't 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
Jaska