Class 11 chemistry ch 8

CLASS 11 chemistry chapter 8 

Chapter 8 Redox Reactions

Redox Reaction Basic Formulas 

Chapter 8 Free

Oxidation

Reduction

1.  Addition of oxygen 1.  Removal of oxygen

2.  Removal of hydrogen 2.  Addition of hydrogen

3.  Addition of an electronegative element 3.  Removal of an electronegative element

4.  Removal of an electropositive element 4.  Addition of an electropositive element

5.  Loss of electron 5.  Gain of electron

Oxidation number denotes theoxidation state of an element in a compound ascertained according to a setof rules formulated on the basis thatelectron in a covalent bond belongsentirely to more electronegative element.

Calculation of oxidation number

1.  O. S. of all the elements in their elemental form (in standard state) is taken as zero O. S. of elements in Cl2, F2, O2, P4, O3, Fe(s), H2, N2, C(graphite) is zero.

2.   Common O. S. of elements of group one (1st) is one. Common O. S. of elements of group two (2nd) is two.

3.  For ions composed of only one atom, theoxidation number is equal to the chargeon the ion.

4.  The oxidation number of oxygen in most compounds is –2.While in peroxides (e.g., H2O2, Na2O2), eachoxygen atom is assigned an oxidationnumber of –1, in superoxides (e.g., KO,RbO2) each oxygen atom is assigned anoxidation number of –(½).

5.  In oxygendifluoride (OF2) and dioxygendifluoride (O2F2), the oxygen is assignedan oxidation number of +2 and +1,respectively.

6.  The oxidation number of hydrogen is +1 but in metal hydride its oxidation no. is–1.

7.  In all its compounds, fluorine has anoxidation number of –1.

8.  The algebraic sum of the oxidation numberof all the atoms in a compound must bezero.

9.  In polyatomic ion, the algebraic sumof all the oxidation numbers of atoms ofthe ion must equal the charge on the ion. 

Stockotation:the oxidationnumber is expressed by putting a Romannumeral representing the oxidation numberin parenthesis after the symbol of the metal inthe molecular formula. Thus aurous chlorideand auric chloride are written as Au(I)Cl andAu(III)Cl3. Similarly, stannous chloride andstannic chloride are written as Sn(II)Cl2andSn(IV)Cl4.

Oxidation: An increase in the oxidationnumber 

Reduction: A decrease in the oxidationnumber

Oxidising agent: A reagent which canincrease the oxidation number of an elementin a given substance. These reagents are calledas oxidants also.

Reducing agent: A reagent which lowers the oxidation number of an element in a givensubstance. These reagents are also called asreductants.

Redox reactions: Reactions which involvechange in oxidation number of the interactingspecie

Equilibrium of oxidation and reduction reactions.

 Oxidation number method.

 Write a pure ionic equation: for potassium dichromate (VI), K2Cr2O7 with sodium sulfate, for Na2SO3 reaction, give chromium ion (III) և sulfate ion with an acid solution.

 Step 1. The structural equation of ion is as follows.  Cr2O72– (aq) + SO32– (aq) → Cr3 + (aq) + SO42– (aq)

 Step 2. Define the oxidation numbers for Cr և S + 6 -2 +4 -2 + 2 +6 -2 Cr2O72– (aq) + SO32– (aq) → Cr3 + (aq) + SO42– (aq)

 Step 3. Calculate the increase in the amount of oxidation. Decrease և equalize it.  +6 -2 +4 -2 + +3 +6 Cr2O72– (aq) + 3SO32– (aq) → 2Cr3 + (aq) + 3SO42– (aq)

 Step 4. Balance the charge by adding H + acid to Cr2O72– (aqueous) + 3SO32- (aq) 8H + → 2Cr3 + (aq) + 3SO42– (aq)

 Step 5. Balance the oxygen atom by adding a water molecule.  Cr2O72– (aq) + 3SO32– (aq) 8H + → 2Cr3 + (aq) + 3SO42– (aq) + 4H2O (l)

 The response method is half the battle

 Balance the equation explaining the oxidation of Fe2 + ions with February 3 + ions with dichromate ions (Cr2O72 - acidic environment, where Cr2 O72 ions are reduced to Cr3 + ions.

 Step 1. Produce an unbalanced equation for ionic treatment.  Fe2 + (aq) + Cr2O72– (aq) → Fe3 + (aq) + Cr3 + (aq)

 Step 2. Separate the equation for half of the reactions.

 Step 3. Balancing the non-O և H atoms of each half-wave reaction.  Cr2O72– (aq) → Cr3 + (aq)

 Step 4. For reactions in an acidic environment, add H2O to the atoms of O և H to compensate for the offset H.Cr2O72– (aq) +14 H + → Cr3 + (aq) + 7H2O (l)

 Step 5. Add electrons in the middle of the reaction to balance the charges.  If necessary, make the number of electrons equal to the binary reactions by multiplying one or two halves of the interaction by the corresponding coefficients.  Fe2 + (aq) → Fe3 + (aq) + e– Cr2O72– (aq) + 14H + (aq) + 6e– → 2Cr3 + (aq) + 7H2O (l) 6Fe2 + (aq) → 6 Fe3 + (aq  )) +6 e–

 Step 6. We add two halves of the reaction to achieve a total response հեռ to remove the electrons on each side.  This gives a pure ionization as follows.  6Fe2 + (aq) + Cr2O72– (aq) + 14H + (aq) → 6Fe3 + (aq) + 2Cr 3+ (aq) + 7H2O (l)

 Decreased spores are defined as a joint oxidized and reduced number of asopenes: an oxidation or reduction reaction.  Introducing Zn2 + / Zn և Cu2 + / Cu.

 v Electrochemical cells are devices used to obtain an electric current through a chemical reaction.

 Electrochemical cells

 Electrochemical cells are devices used to obtain an electric current through a chemical reaction.

 The voltage across each electrode is known as the voltage across the electrode.  If each type of concentration involved in the electrode reaction is a unit (if any gas appears in the reaction of the electrodes, it is limited to one atmospheric pressure), and further treatment is performed at 298 A, then it is said that the potential of each electrode is standard electric.  is voltage.

 • SHE is used to measure the load voltage, and its standard load voltage is taken as 0.00 V.

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 Chapter ցուց List of Materials:

 The head has some basic concepts of chemistry

 Chapter 2 Atom structure

 Chapter 3 Classification of Periodic Elements into the Properties of Elements

 Chapter IV Chemical bond: Molecular structure

 Chapter 5 Articles:

 Chapter 6 m Hermodynamics

 Chapter Eleven P-Block Element

 Chapter Seven Remains

 Chapter 8 Redox Reactions:

 Chapter X - block element

 Chapter Twelve Organic Chemistry.  Some basic principles and methods

 Chapter 13 Carbohydrates

 Chapter Fourteen Environmental Chemistry

 Download lesson 6 to 12 in PDF format