REDOX REACTIONS: REDOX REACTIONS IN TERMS OF ELECTRON TRANSFER REACTIONS

Half reactions that involve loss of electrons are called oxidation reactions. Similarly, the. half reactions that involve gain of electrons are called reduction reactions We have already learnt that the reaction. Is redox reaction because in this reaction sodium is oxidised due to the addition of either oxygen or more electronegative element to sodium. Simultaneously, chlorine, is reduced, the electro positive element sodium has been added as sodium chloride, which is ionic compound and perhaps better written as Na+Cl-- s. Development of charges on the species produced suggests us to rewrite the reaction 10 in the following manner :Each of the above processes can be considered as two separate steps, one involving the loss of electrons and the other the gain of electrons. Each of the above steps is called a half reaction, which explicitly shows involvement of electrons. Sum of the half reactions gives the overall reaction :

In reactions 10 sodium, which is oxidised, acts as a reducing agent because it donates electron to each of the elements interacting with it and thus helps in reducing them. Chlorine is reduced and act as oxidising agent because it accept electrons from sodium. Competitive Electron Transfer Reactions. Place a strip of metallic zinc in an aqueous solution of copper nitrate for about one hour. You may notice that the strip becomes coated with reddish metallic copper and the blue colour of the solution d is appears. Formation of Zn2+ ions among the products can easily be judged when the blue colour of the solution due to Cu2+ has disappeared. If hydrogen sulphide gas is passed through the colour less solution containing Zn2+ ions, appearance of white zinc. sulphide, Zn S can be seen on making the solution alkaline with ammonia. The state of equilibrium for the reaction represented by equation 11. For this purpose, let us place a strip of metallic copper in a zinc sulphate solution. No visible reaction is noticed and. attempt to detect the presence of Cu2+ ions by passing H2S gas through the solution to produce the black colour of cup ric sulphide,Cu S, does not succeed.

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