A reaction in which a reducing agent loses electrons while it is oxidized and the oxidizing agent gains electrons while it is reduced is called as redox (oxidation – reduction) reaction. An unbalanced redox reaction can be balanced using this calculator.

Calculator of Balancing Redox Reactions

Redox Reaction is a chemical reaction in which oxidation and reduction occurs simultaneously and the substance which gains electrons is termed as oxidizing agent.
Refer the following table which gives you oxidation numbers.

Table of Common Ions

Positive Ions

Valency 1 Valency 2 Valency 3
Lithium Li+ Magnesium Mg2+ Aluminium Al3+
Sodium Na+ Calcium Ca2+ Iron III Fe3+
Potassium K+ Strontium Sr2+ Chromium Cr3+
Silver Ag+ Barium Ba2+
Hydronium H3O+ Copper II Cu2+
Hydrogen H+ Lead II Pb2+
Ammonium NH4+ Zinc Zn2+
Copper I Cu+ Manganese II Mn2+
Mercury I Hg+ Iron II Fe2+
Tin II Sn2+

Negative Ions

Valency 1 Valency 2 Valency 3
Fluoride F Oxide O2- Phosphate PO43-
Chloride Cl Sulphide S2-
Bromide Br Carbonate CO32-
Iodide I Sulphate SO42-
Hydroxide OH Sulphite SO32-
Nitrate NO3 Dichromate Cr2O72-
Bicarbonate HCO3 Chromate CrO42-
Bisulphate HSO3 Oxalate C2O42-
Nitrite NO2 Thiosulphate S2O32-
Chlorate ClO3 Tetrathionate S4O62-
Permanganate MnO4 Monohydrogen Phosphate HPO42-
Hypochlorite OCl
Dihydrogen Phosphate H2PO4

 

Example: 1

Balance the given redox reaction:

H2+ + O22- -> H2O

Considering the equation above, we have 2 hydrogen (H) with the total charge +1[Refer the charges of the elements in the above table] and 2 oxygen (O) with the total charge -2 on the L.H.S and 2 hydrogen (H) with total charge +2 and only 1 oxygen (O) with the total charge -2 on the R.H.S. Hence with the unequal number of oxygen molecule charges, the chemical equation is said to be unbalanced.

How to balance an unbalanced chemical equation?

Let us learn here how to balance the above unbalanced equation using half reaction method with step by step procedure.

Given,

H+12 + O-22 -> H+12 O-2

To balance the unbalanced oxygen molecule charges, we add 2 in front of the product on R.H.S.
We get,

 

H+12 + O-22 -> (2) H+12 O-2

Now, we have 2 Oxygen’s with the total charge -2 but 4 Hydrogen’s with the total charge +4 on the R.H.S.
In order to balance the same, we add an another 2 in front of Hydrogen on the L.H.S

 

(2) H+12 + O-22 -> (2) H+12 O-2

Now, the equation is balanced with 4 Hydrogen’s (H) with total charge +4 and 4 Oxygen’s with total charge -4 on both sides.

Example: 2

Cr+3 + Cl-1 = Cr+3 + Cl-12

Considering the equation above, we have 1 chromium (Cr) with the total charge +3[Refer the charges of the elements in the above table] and 1 chloride (Cl) with the total charge -1 on the L.H.S and 1 chromium (Cr) with total charge +3 and only 2 chloride(Cl) with the total charge -1 on the R.H.S. Hence with the unequal number of oxygen molecule charges the chemical equation is said to be unbalanced.

How to balance an unbalanced chemical equation?

Let us learn here how to balance the above unbalanced equation with step by step procedure.

Given:

Cr+3 + Cl-1 = Cr+3 + Cl-12

To balance the unbalanced chloride molecule charges, we add 2 in front of the chloride on L.H.S.
We get,

Cr+3 + (2)Cl-1 = Cr+3 + Cl-12

Now, the equation is balanced with 2 Chloride’s (Cl) with total charge -2 and 3 Chromium’s with total charge +3 on both sides.
This is how the redox equations are balanced.

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