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Oxidation Number - Applications and Limitations

Introduction The concept of electron transfer is found unable to explain the redox changes or electron shift in case of covalent compounds. To explain these changes a new concept, called oxidation number is introduced. Oxidation number is defined as the charge that an atom of the element has in it's ion or appear to have when present in the combined state with other atoms. Or In other words, it is also defined as the charge that an atom appear to have in a compound when all other atoms are removed as ions from the compound. Applications of Oxidation Number The important applications of Oxidation no. are as follows: (a) Stock Notation The names of the compounds of metals showing more than one oxidation state are written by putting a Roman numeral like I, II, III.... indicating the oxidation state of the metal within the parenthesis after the symbol and name of the element. This system was introduced by Alfred Stock , a

Balancing a Redox Reaction by Half-Reaction method

In this method, the two half equations are balanced separately and then added together to give balanced equation.The following steps are involved in this method: Produce unbalanced equation for the reaction in ionic form. Separate the equation into half-reactions (i.e., oxidation half and reduction half). Balance the atoms other than H and O in each half reaction individually. For reactions occurring in acidic medium, add H2O to balance O atoms and H+ to balance H atoms. Add electrons to one side of the half reaction to balance the charges. If need be, make the no. of electrons equal in the two half reactions by multiplying one or both half reactions by appropriate number. Add the two half reactions to achieve the overall reaction and cancel the electrons on each side to get the net ionic equation. Verify that the equation contains the same type and number of atoms and the same changes on both sides of the equation. This last check reveals that the equation

Balancing a Redox Reaction by Oxidation no. method

In writing equations for oxidation-reduction reactions, just as for other reactions, the compositions and formulas must be known for the substances that reacts and for the products that are formed. The oxidation No. method is now best illustrated in the following steps: Write the correct formula for each reactant and product. Identify atoms which undergo change in oxidation number in the reaction by assigning the oxidation number to all elements in the reaction. Calculate the increase or decrease in oxidation number per atom and for the entire molecule/ion in which it occurs. If these are not equal then multiply by suitable no. so that these become equal. (If you realise that two substances are reduced and nothing is oxidised or vice-versa, something is wrong. Either the formulas of reactants or products are wrong or the oxidation no.s have not been assigned properly). Ascertain the involvement of ions if the reaction is taking place in water, add H+ or OH- ions t

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