How do you reduce Fe3+ to Fe2+?

Q: What can reduce Fe3+?

Both the Tml and Fe3O4@Tml systems can reduce Fe3+ to Fe2+, with reduction amounts of 35.70 ± 0.29 M (Tml) and 26.17 ± 0.57 M (Fe3O4@Tml), respectively. Fe3+ was reduced by electrons obtained from OH–, and the free energy change of the reaction was −2.954 eV.

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Fe(3+)-Fe(2+) transformation method: an important antioxidant assay
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How can you reduce Fe3+ to Fe2+?
Will Fe reduce Fe3+ to Fe2+?
What can reduce Fe3+?
Which reducing agent is used to convert ferric to ferrous ions?

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Hint: Recollect the concept of redox reactions. Here the question says, ferric ion is reduced to ferrous ion. So, reduction reaction is taking place and ferric ion is gaining one electron to form ferrous ion. Take a look at each of the reactants given in the options and then choose the reactant which can act as a reducing agent.

Complete answer:
- Iron is a transition metal which can exist in two oxidation states.
- One is ferrous ion, $F{{e}^{2+}}$ which has +2 oxidation state and another one is ferric ion, $F{{e}^{3+}}$ which has +3 oxidation state.
- Now, in the question, ferrous ions are getting reduced to ferric ions.
- Reduction is the process which involves gain of electrons.
- For the reduction process to take place, free electrons should be present in the reaction medium which also indicates that the reacting species should donate electrons and therefore, the reactant should be a reducing agent.
- A reducing agent is the reagent which reduces other reactants by itself getting oxidized.
- Hydrogen peroxide acts as a reducing agent in the basic medium and reduces $F{{e}^{3+}}$ to $F{{e}^{2+}}$. The reaction is given as,
\[2F{{e}^{3+}}+{{H}_{2}}{{O}_{2}}+2O{{H}^{-}}\to 2F{{e}^{2+}}+{{O}_{2}}+2{{H}_{2}}O\]
- $N{{a}_{2}}{{O}_{2}}$ in water will also act as a reducing agent since hydrogen peroxide and sodium hydroxide is formed when $N{{a}_{2}}{{O}_{2}}$ is added to water.
\[N{{a}_{2}}{{O}_{2}}+2{{H}_{2}}O\to 2NaOH+{{H}_{2}}{{O}_{2}}\]
\[2F{{e}^{3+}}+{{H}_{2}}{{O}_{2}}+2O{{H}^{-}}\to 2F{{e}^{2+}}+{{O}_{2}}+2{{H}_{2}}O\]

Therefore, the answer is both options (A) and (B).

Note:
Remember sulphuric acid is a strong oxidizing agent so in acidic medium, reduction will not take place. Only in the basic medium, hydrogen peroxide will get oxidized to oxygen and water giving rise to two free electrons and therefore, hydrogen peroxide will act as a reducing agent in the basic medium.

The Table of Standard Reduction Potentials gives a reduction potential of 0.771 V for the reduction of Fe3+(aq) to Fe2+(aq) under standard acidic conditions. What is the reduction potential under standard basic conditions?

There appears to be no explicit pH dependence in the reduction under standard acidic conditions:

Fe3+(aq) + e– → Fe2+(aq)

However, this does not take into account all of the reactivity under basic conditions. Under standard basic conditions (1.00 M OH–, pH = 14.00) both iron cations will precipitate as hydroxide salts:

Fe(OH)3(s) + e– → Fe(OH)2(s) + OH–(aq)

Thus, the contribution of the precipitation chemistry must also be accounted for in determining the reduction potential.

Fe3+(aq) + e– → Fe2+(aq) E°red = 0.771 V ΔG° = –nFE° = –(1)(96485)(0.771) = –74400 J
Fe(OH)3(s) → ← Fe3+(aq) + 3 OH–(aq) Ksp = 4×10–38 ΔG° = –RTlnKeq = –(8.314)(298)ln(4×10–38) = +213000 J
Fe2+(aq) + 2 OH–(aq) → ← Fe(OH)2(s) Keq = 1/Ksp = 1/8.0×10–16 = 1.3×1015 ΔG° = –RTlnKeq = –(8.314)(298)ln(1.3×1015) = –86200 J

Add the three reactions together to give the net reaction:

Fe(OH)3(s) + e– → Fe(OH)2(s) + OH–(aq)
ΔG° = –74400 + 213000 –86200 = 52000 J
E° = –ΔG°/nF = –(52000)/(1)(96485) = –0.54 V

Fe(3+)-Fe(2+) transformation method: an important antioxidant assay

İlhami Gülçin. Methods Mol Biol. 2015.

Abstract

If we look at the multitude of varied and interesting reaction that constitute biochemistry and bioorganic chemistry, it is possible to classify a great many as either oxidation or reduction reactions. The reducing agent transfers electrons to another substance and is thus it oxidized. And, because it gives electrons, it is also called an electron donor. Electron donors can also form charge transfer complexes with electron acceptors. Reductants in biochemistry are very diverse. For example ferric ions (Fe(3+)) are good reducing agents. Also, different bioanalytical reduction methods are available such as Fe(3+)-ferrous ions (Fe(2+)) reduction method, ferric reducing antioxidant power reducing assay. In this section, Fe(3+)-Fe(2+) transformation will be discussed. Recently there has been growing interest in research into the role of plant-derived antioxidants in food and human health. The beneficial influence of many foodstuffs and beverages including fruits, vegetables, tea, coffee, and cacao on human health has been recently recognized to originate from their antioxidant activity. For this purpose, the most commonly method used in vitro determination of reducing capacity of pure food constituents or plant extracts is Fe(3+) reducing ability. This commonly used reducing power method is reviewed and presented in this study. Also, the general chemistry underlying this assay was clarified. Hence, this overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. In addition, the most important advantages of this method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of Fe(3+)-Fe(2+) transformation assay are outlined and critically discussed.

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How can you reduce Fe3+ to Fe2+?

This means that if you combine Fe3+ solution with Hydrogen gas, Fe3+ should be reduced to Fe2+ and hydrogen gas should be oxidized.

Will Fe reduce Fe3+ to Fe2+?

Fe3+ is reduced to Fe2+ by using. Uh-Oh!

What can reduce Fe3+?

Both the Tml and Fe₃O₄@Tml systems can reduce Fe³⁺ to Fe²⁺, with reduction amounts of 35.70 ± 0.29 M (Tml) and 26.17 ± 0.57 M (Fe₃O₄@Tml), respectively. Fe³⁺ was reduced by electrons obtained from OH^–, and the free energy change of the reaction was −2.954 eV.

Which reducing agent is used to convert ferric to ferrous ions?

The basic concept that hydrogen can be used to reduce ferric ion back to ferrous ion for recycling to a copper electrowinning process has been shown to work. Further, carbon monoxide, a byproduct of the production of hydrogen, can also reduce ferric ion although the rates are slower.