The Student Room Group

help on balancing equation!

i am unsure how to balance this equation can someone help, thanks!

Fe2+ + H2O2 + H+ --> Fe3+ +H20
Original post by Ashirs
i am unsure how to balance this equation can someone help, thanks!

Fe2+ + H2O2 + H+ --> Fe3+ +H20

hiya,

okay so you need to balance the irons so there are now 6 on each side.

this gets you to:
3Fe^2 + H^2O^2 + H —> 2Fe^3 + H^2O

Then you need to balance the oxygens so add a two to the water molecule on the end.

This gets you to:
3Fe^2 + H^2O^2 + H —> 2Fe^3 + 2H^2O

so now your irons and oxygens are balanced, but you have 3 hydrogens on the left and 4 on the right. so to balance this out, you need to add a 2 to the hydrogen so both sides have 4.

So the final answer should be (if i’ve done this right):

3Fe^2 + H^2O^2 + 2H —> 2Fe^3 + 2H^2O

sorry if that’s wrong aha.

the ^ means the little numbers btw.

also i’d suggest you write it out normally cause it’s harder to understand when it’s typed

hope this helps :smile:
Original post by Ashirs
i am unsure how to balance this equation can someone help, thanks!

Fe2+ + H2O2 + H+ --> Fe3+ +H20


I’d think about it in terms of the individual half equations.

In the oxidation process, the Fe^2+ loses an electron to become Fe^3+:

Fe^2+ —> Fe^3+ + e^-

In the reduction process, the hydrogen ions and hydrogen peroxide are reduced to water:

H2O2 + H+ + e^- —> H2O

But clearly this reduction equation isn’t balanced.

Notice how there are 2 oxygens on the left hand side and there’s only 1 on the right? That suggests we should double up the number of water molecules formed. But that requires an extra hydrogen ion and electron to balance out the hydrogens and the charges, so:

H2O2 + 2H^+ + 2e^- —> 2H2O

Now to cancel the electrons, we double up the oxidation process, then add our equations:

2Fe^2+ —> 2Fe^3+ + 2e^-

So:

2Fe^2+ + H2O2 + 2H^+ + 2e^- —> 2Fe^3+ + 2H2O + 2e^-

Cancelling the electrons:

2Fe^2+ + H2O2 + 2H^+ —> 2Fe^3+ + 2H2O
Original post by penelopejc
hiya,

okay so you need to balance the irons so there are now 6 on each side.

this gets you to:
3Fe^2 + H^2O^2 + H —> 2Fe^3 + H^2O

Then you need to balance the oxygens so add a two to the water molecule on the end.

This gets you to:
3Fe^2 + H^2O^2 + H —> 2Fe^3 + 2H^2O

so now your irons and oxygens are balanced, but you have 3 hydrogens on the left and 4 on the right. so to balance this out, you need to add a 2 to the hydrogen so both sides have 4.

So the final answer should be (if i’ve done this right):

3Fe^2 + H^2O^2 + 2H —> 2Fe^3 + 2H^2O

sorry if that’s wrong aha.

the ^ means the little numbers btw.

also i’d suggest you write it out normally cause it’s harder to understand when it’s typed

hope this helps :smile:


Unfortunately, the law of conservation of mass would disagree with your equation.

Count the numbers of each element on each side and work out why. (Note that with the iron, it’s ions, not molecules, thus Fe^2 and Fe^3 have been taken to mean Fe^2+ and Fe^3+, respectively)
(edited 1 year ago)
I think balancing equations is just a matter of practice and learning a few simple rules, practice with some of the equations in the links then try the one in your question

https://science-revision.co.uk/balancing%20equations.html

https://chemguide.co.uk/14to16/equations/equations.htm
Reply 5
thank you!!!
Reply 7
thank you!

Quick Reply

Latest