REDOX REACTIONS  

Oxidation : i. The addition of oxygen to a substance is called oxidation. ii. The removal of hydrogen from a substance is also called oxidation. Reduction : i. The addition of hydrogen to a substance is called reduction. ii. The removal of oxygen from a substance is also called reduction. Moreover, oxidation and reduction occurs  together. Oxidisingagent : i. The substance which gives oxygen for oxidation is called an oxidisingagent. ii. The substance which removes hydrogen is also called an oxidisingagent. Reducing agent : i. The substance which gives hydrogen for reduction  is called a  reducing agent. ii. The substance which removes oxygen  is also called a reducing agent. The oxidation and reduction reactions are  also  called redoxreactions.

Dr. DarshanaBawankule2020                    Les. Chemical reactions and Equations 57

REDOX REACTIONS • Examples : 1. When copper oxide is heated with hydrogen, then copper metal and water are formed: CuO +     H2 Heat    Cu      +      H2O Copper oxide   Hydrogen        Copper       Water In the above reaction, CuOis changing into Cu. That is oxygen is being removed from copper oxide. i. So by definition, removal of oxygen from a substance is called reduction, so we can say that copper oxide is reduced to copper. ii. H2 is changing into H2O. That is, oxygen is being added to hydrogen. So by definition, addition of oxygen to a substance is called oxidation. So hydrogen is being oxidisedto water. Removal of oxygen: Reduction  

CuO +     H2 Heat    Cu      +      H2O

Addition of oxygen : Oxidation Copper oxide is the oxidisingagent & hydrogen is the reducing agent.

Dr. DarshanaBawankule2020                    Les. Chemical reactions and Equations 58

REDOX REACTIONS

i. Substance oxidised : H2 ii. Substance  reduced : CuO iii. Oxidisingagent       : CuO iv. Reducing agent       : H2 The substance which gets reduced (CuO) is the oxidisingagent and the substance which gets oxidisedis the reducing agent. The reaction between copper oxide and hydrogen to form copper and water is an oxidation-reduction reaction which is also a displacement reaction.

2. When hydrogen sulphidereacts with chlorine, then sulphurand hydrogen chloride is formed: H2S            +      Cl2 S         +        2HCl Hydrogen sulphide Chlorine           Sulphur Hydrogen chloride i. Substance oxidised : H2S ii. Substance reduced    : Cl2 iii. Oxidisingagent           : Cl2 iv. Reducing agent           : H2S

Dr. DarshanaBawankule2020                    Les. Chemical reactions and Equations REDOX REACTIONS  

Oxidation : i. The addition of oxygen to a substance is called oxidation. ii. The removal of hydrogen from a substance is also called oxidation. Reduction : i. The addition of hydrogen to a substance is called reduction. ii. The removal of oxygen from a substance is also called reduction. Moreover, oxidation and reduction occurs  together. Oxidisingagent : i. The substance which gives oxygen for oxidation is called an oxidisingagent. ii. The substance which removes hydrogen is also called an oxidisingagent. Reducing agent : i. The substance which gives hydrogen for reduction  is called a  reducing agent. ii. The substance which removes oxygen  is also called a reducing agent. The oxidation and reduction reactions are  also  called redoxreactions.

Dr. DarshanaBawankule2020                    Les. Chemical reactions and Equations 57

REDOX REACTIONS • Examples : 1. When copper oxide is heated with hydrogen, then copper metal and water are formed: CuO +     H2 Heat    Cu      +      H2O Copper oxide   Hydrogen        Copper       Water In the above reaction, CuOis changing into Cu. That is oxygen is being removed from copper oxide. i. So by definition, removal of oxygen from a substance is called reduction, so we can say that copper oxide is reduced to copper. ii. H2 is changing into H2O. That is, oxygen is being added to hydrogen. So by definition, addition of oxygen to a substance is called oxidation. So hydrogen is being oxidisedto water. Removal of oxygen: Reduction  

CuO +     H2 Heat    Cu      +      H2O

Addition of oxygen : Oxidation Copper oxide is the oxidisingagent & hydrogen is the reducing agent.

Dr. DarshanaBawankule2020                    Les. Chemical reactions and Equations 58

REDOX REACTIONS

i. Substance oxidised : H2 ii. Substance  reduced : CuO iii. Oxidisingagent       : CuO iv. Reducing agent       : H2 The substance which gets reduced (CuO) is the oxidisingagent and the substance which gets oxidisedis the reducing agent. The reaction between copper oxide and hydrogen to form copper and water is an oxidation-reduction reaction which is also a displacement reaction.

2. When hydrogen sulphidereacts with chlorine, then sulphurand hydrogen chloride is formed: H2S            +      Cl2 S         +        2HCl Hydrogen sulphide Chlorine           Sulphur Hydrogen chloride i. Substance oxidised : H2S ii. Substance reduced    : Cl2 iii. Oxidisingagent           : Cl2 iv. Reducing agent           : H2S

Dr. DarshanaBawankule2020                    Les. Chemical reactions and Equations