RBSE Class 11 Chemistry Notes Chapter 8 Redox Reactions

These comprehensive RBSE Class 11 Chemistry Notes Chapter 8 Redox Reactions will give a brief overview of all the concepts.

RBSE Class 11 Chemistry Chapter 8 Notes Redox Reactions

→ In redox or oxidation-reduction reactions, one substance is oxidised and other substance is reduced.

→ Oxidation: The term oxidation is defined as the addition of oxygen/electronegative element to a substance or removal of hydrogen/ electropositive element from a substance. Oxidation is also known as de-electronation.

→ Reduction: The term reduction means removal of oxygen or electronegative element from a substance or addition of hydrogen or electro-positive element to a substance. In reduction, electrovalency of an element decreases. Reduction is also known as electronation.

→ Oxidising Agent: Oxidising agent is a substance which oxidises a substance and accepts electronsor itself gets reduced.

→ Reducing Agent: Reducing agent is a substance which reduces a substance and itself gets oxidised by losing electrons.

→ Oxidation Reaction: That chemical reaction in which there is exponential decrease in oxidation number of atoms, ions, element or molecule is called oxidation reaction.

→ Reduction Reactions: That chemical reaction in which there is exponential increase in oxidation number of atoms, ions, element or molecule is called oxidation reaction.

→ Redox Reactions: Those reactions in which oxidation and reduction takes place simultaneously are called redox reactions.

→ Oxidising Reducing Agents: Those substances which can act both as oxidants and reductants are called oxidising reducing agents.

→ Reduction Half Reactions: In these reactions, gain of electrons takes place.

→ Oxidation Half Reactions: In these reactions, loss of electrons takes place.

→ Oxidation Number: The effective charge oh the , atoms of a substance which are assigned in accordance with a consistent set of rules is called oxidation number. It is also known as oxidation state. Its value may be positive, negative or zero.

→ An element has different oxidation number in different compounds and conditions.

→ Increase in oxidation number increases strength of an acid whereas strength of base decreases.

→ To balance redox reactions, two methods are used:

• Ion electron method: Based on the principle that number of electrons accepted is equal to number of electrons lost,
• Oxidation number method: Based on the principle that increases in oxidation number is equal to decreases in oxidation number.

→ Equivalent Mass of Oxidising Agent = Atomic mass or molecular mass or ionic mass of oxidising agent/Electrons accepted or change in oxidation number.

→ Equivalent Mass of Reducing Agent = Atomic mass or molecular mass or ionic mass of reducing agent/Electrons lost or change in oxidation number.

→ Electrochemical cell: The appliance in which redox reactions takes place indirectly and release energy is reflected in the form is electrical energy is called electrochemical cell.

→ Electrode Potential: The potential difference between a metal and its ion when a metal electrode is dipped in a salt solution, is known as electrode potential.

→ Standard Electrode Potential: If the concentration of solution is 1 mole and temperature is 298 K. then potential difference is called standard electrode potential.

→ Electrochemical Series: The arrangement of elements in order of increasing reduction potential values is called electrochemical series. It is also known as activity series.On moving down the series, reactivity decreases and metallic property decreases.

→ To verify that a given reaction is feasible or not can be found out by calculating the difference between standard electrode potentials of two half cells. If the value of E0 is positive, reaction is feasible and if E 0 value is negative, reaction is not possible.

→ Important Facts:

• In oxidation reaction, loss of electrons takes place.
• In reduction reaction, gain of electrons takes place.
• Reducing agent is a species which loses electrons.
• Oxidising agent is a species which accepts electrons.
• In redox reactions, oxidation and reduction takes place simultaneously.
• Oxidation numbers are assigned in accordance with a consistent set of rules.
• During reduction, there is decrease in oxidation number.
• During oxidation, there is increase in oxidation number.
• Electrochemical cell is a device change is free energy is reflected in the form of electrical energy. In this, indirect redox reactions tak'es place.
• In an electro-chemical series, metals are arranged in the order of their standard reduction potentials.