oxidant and reductant

1. Oxidant and reductant

2. • An oxidant is a substance that accepts or receives electron from another substance, hence, is consequently reduced. Since it accepts electrons it is also called an electron acceptor. • Introduction Oxidants produced by phagocytes as observed in vivo act as tumor promoters or co-carcinogens rather than as complete carcinogens maybe because of the high levels of endogenous antioxidant defenses. They may also be involved in the oxidative damage in joints as they can cause an autoimmune response. • •

3. Chemical Oxidation • Chemical oxidation occurs when one or more electrons are lost within a substance through contact with and reaction to an oxidant. An example of this is when iron comes in contact with oxygen (an oxidant) and moisture. The reaction corrodes the iron and produces a red-orange residue. This is an oxidation process is called rusting. Oxidation on a chemical level is also used commercially through "oxidation technologies." These technologies are derived from catalyzing the oxidation of contaminated soil, wastewater and other material. various substances to treat

4. Biological oxidation • Like chemical oxidation, biological oxidation occurs when electrons are removed from a substance. However, the processes diverge with biological oxidation taking place on a different atomic or molecular level. For instance, glucose is oxidized when hydrogen atoms are removed and combined with an oxidant during the process of cellular respiration. This type of biological oxidation is a beneficial process that creates energy for an organism.

5. Biological oxidation • Other forms of biological oxidation can be harmful to an organism. These interactions involve oxidants that damage biological material such as DNA and protein, contributing to degenerative diseases. These oxidants are created by natural processes such as metabolism. Negative forms of oxidation such as this, have generated a plethora of health information pertaining to substances that can help offset the interactions. These counteracting substances are called antioxidants.

6. Oxidation reaction • Oxidation reactions can be defined in terms of addition of oxygen or the removal of hydrogen. There are a number of reactions in which oxygen is added, or in which hydrogen is removed. • Oxidation:- Loss of electron Zn →Zn2+ +2e- • Examples: Addition of Oxygen: CuO(s) H2(g) → Cu(s) H2O(l) CuO adds oxygen to H2; CuO is therefore the oxidizing agent or oxidant, it oxidizes the H2to H2O.

7. •Removal of Hydrogen: (a). H2S(g) + Cl2(g) → 2HCl(g) + S(s) Chlorine is the oxidant, it removes hydrogen from H2S, thereby oxidizing it to sulphur. (b). 2H2O(l) + 2F2(g) → 4HF(aq) + O2(g) Fluorine removes hydrogen from the water, therefore, fluorine is the oxidant. The water is oxidized to oxygen.

8. Reduction Reaction • Reduction reactions can be defined as reactions that involve the removal of oxygen or the addition of hydrogen. • Reduction: Gain Of electron • Example : (Zn2+) + (2e-) →Zn • Removal of Oxygen: CuO(s) H2(g) → Cu(s) H2O(l) • Hydrogen removes oxygen from CuO, thereby reducing it to Cu. Hydrogen is therefore the reducing agent or reductant •

9. • Addition of Hydrogen: . (a). H2S(g) Cl2(g) → 2HCl(g) S(s) H2S adds hydrogen to Cl2(g). H2S is the reducing agent. It reduces Cl2(g) to HCl(g). (b). 2H2O(l) 2F2(g) → 4HF(aq) O2(g) H2O here adds hydrogen to F2, thereby reducing it to HF. H2O is the reductant in this reaction.

10. Note : • In a redox reaction, an oxidizing agent is the substance which accepts electrons and become reduced. • A reducing agent is the substance which donates electrons and become oxidized. • Oxidation leads to increase in oxidation number. • Reduction leads to decrease in oxidation number. • The reducing agent (reductant), which is oxidized increases in oxidation number (i.e., loss of electrons increases oxidation number) •

11. • Metals are usually reducing agents – they have high electropositivity. They reduce their counterparts in redox reactions by donating electrons to them, while they themselves become oxidized (i.e. increase in oxidation number). Example, K, Na, Ca and Mg. • • Non-metals have high electronegativity (i.e. they accept electrons readily). They therefore act as oxidizing agents, and become reduced. Examples, F2, O2, Cl2.