How many electrons are transferred in the reaction of hydrogen peroxide with iron (II) ion in
acidic solution to form iron (III) ion and water?
I looked up two half reactions form a "Standard Reduction Potentials" table. The 2nd half reaction occurred in reverse as an oxidation. I doubled this reaction so that the number of electrons gained and lost are equal. Then I combined the two half reactions into an overall reaction. This is needed to see how many electrons are transferred from H2O2 to Fe^+2. [Unless you have studied this material in your chemistry class it may be confusing.]
The two half reactions are:
H2O2 + 2H+(aq) + 2e- --> 2H2O (reduction)
2Fe^+2(aq) --> 2Fe^+3(aq) + 2e- (oxidation)
The overall reaction is:
H2O2 + 2H+(aq) + 2e- + 2Fe^+2(aq) --> 2H2O + 2Fe^+3(aq) + 2e-
or
H2O2 + 2H+(aq) + 2Fe^+2(aq) --> 2H2O + 2Fe^+3(aq)
The above show 2 electrons going to a molecule of H2O2 from two Fe^+2 ions which oxidize to form two Fe^+3 ions.
Balance the equation: MnO4¡V + H+ + Fe2+ Mn2+ + H2O + Fe3
To determine the number of electrons transferred in a reaction, we need to examine the oxidation states of the elements involved before and after the reaction.
Let's start by looking at the oxidation state of hydrogen peroxide (H2O2). Hydrogen peroxide is a neutral compound, so the sum of the oxidation states of hydrogen and oxygen must equal zero.
Let's assume the oxidation state of oxygen in hydrogen peroxide is -2. By using this assumption, we can calculate that the oxidation state of hydrogen in hydrogen peroxide is +1.
Next, let's consider the iron(II) ion (Fe2+) and the iron(III) ion (Fe3+). Metal ions, such as iron, have a fixed oxidation state. In this case, iron has an oxidation state of +2 in the iron(II) ion (Fe2+) and +3 in the iron(III) ion (Fe3+).
Now, in the reaction, hydrogen peroxide (H2O2) is being oxidized to form water (H2O), while iron(II) ion (Fe2+) is being oxidized to form iron(III) ion (Fe3+).
H2O2 -> H2O (oxidation of hydrogen peroxide)
Fe2+ -> Fe3+ (oxidation of iron(II) ion)
By comparing the oxidation states of the elements before and after the reaction, we can see that the oxidation state of hydrogen changes from +1 to 0 (a decrease of 1), which means it gains one electron. Therefore, two electrons are gained overall in the oxidation of hydrogen peroxide (since there are two hydrogen peroxide molecules).
Similarly, the oxidation state of iron changes from +2 to +3 (an increase of 1), which means it loses one electron. Therefore, two electrons are lost overall in the oxidation of iron(II) ion (since there are two Fe2+ ions).
Therefore, in the reaction of hydrogen peroxide with iron(II) ion in acidic solution to form iron(III) ion and water, a total of four electrons are transferred.