Advanced Inorganic Chemistry


In the ion-electron method (also called the half-reaction method), the redox equation is separated into two half-equations - one for oxidation & one for reduction. Each of these half-reactions is balanced separately và then combined lớn give the balanced redox equation.

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Step 1. Write down the unbalanced equation ("skeleton equation") of the chemical reaction. All reactants & products must be known. For a better result write the reaction in ionic form.

Step 2. Separate the redox reaction into half-reactions. A redox reaction is nothing but both oxidation and reduction reactions taking place simultaneously.

a) Assign oxidation numbers for each atom in the equation. Oxidation number (also called oxidation state) is a measure of the degree of oxidation of an atom in a substance (see: Rules for assigning oxidation numbers).

b) Identify & write out all redox couples in reaction. Identify which reactants are being oxidized (the oxidation number increases when it reacts) và which are being reduced (the oxidation number goes down).

c) Combine these redox couples into two half-reactions: one for the oxidation, & one for the reduction (see: Divide the redox reaction into two half-reactions).

Step 3. Balance the atoms in each half reaction. A chemical equation must have the same number of atoms of each element on both sides of the equation. Showroom appropriate coefficients (stoichiometric coefficients) in front of the chemical formulas. Never change a formula when balancing an equation. Balance each half reaction separately.

a) Balance all other atoms except hydrogen và oxygen. We can use any of the species that appear in the skeleton equations for this purpose. Keep in mind that reactants should be added only to lớn the left side of the equation và products khổng lồ the right.

b) Balance the oxygen atoms. Kiểm tra if there are the same numbers of oxygen atoms on the left and right side, if they aren"t equilibrate these atoms by adding water molecules.

c) Balance the hydrogen atoms. Kiểm tra if there are the same numbers of hydrogen atoms on the left và right side, if they aren"t equilibrate these atoms by adding protons (H+).

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Step 4. Balance the charge. Khổng lồ balance the charge, add electrons (e-) khổng lồ the more positive side lớn equal the less positive side of the half-reaction. It doesn"t matter what the charge is as long as it is the same on both sides.

Step 5. Make electron gain equivalent khổng lồ electron lost. The electrons lost in the oxidation half-reaction must be equal the electrons gained in the reduction half-reaction. To lớn make the two equal, multiply the coefficients of all species by integers producing the lowest common multiple between the half-reactions.

Step 6. địa chỉ cửa hàng the half-reactions together. The two half-reactions can be combined just lượt thích two algebraic equations, with the arrow serving as the equals sign. Recombine the two half-reactions by adding all the reactants together on one side and all of the products together on the other side.

Step 7. Simplify the equation. The same species on opposite sides of the arrow can be canceled. Write the equation so that the coefficients are the smallest set of integers possible.

Finally, always check to see that the equation is balanced. First, verify that the equation contains the same type and number of atoms on both sides of the equation.

Fe3*1 3*10
N3*2 + 8*1 3*3 + 5*10
O3*6 + 8*3 3*9 + 5*1 + 10*10
H8*1 + 12*1 10*20

The difference between atoms on the left & right side of the equation is not equal to lớn zero.

The error most likely occurred while balancing atoms in the partial equations of oxidation và reduction (Step 3.a). You can resolve this by writing the equation in ionic form. For example, the program won"t correctly balance a equation such as Na2S2O3 + I2 = Na2S4O6 + NaI while the same equation with only NaI written in ionic khung (Na2S2O3 + I2 = Na2S4O6 + Na+ + I-) will be balanced with ease. Carefully reviews the procedure. The wise man learns from the mistakes of others.

Balance the equation with the ARS method → Fe(NO3)2 + HNO3 = Fe(NO3)3 + NO + H2O.

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Citing this page:

Generalic, Eni. "Balancing redox reactions by the ion-electron method." EniG. Periodic Table of the Elements. KTF-Split, 25 Jan. 2022. Web. Date of access. .


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