Factors Affecting Rate of a Chemical Reaction-Nature of the Reactant, Concentration of the Reactants, Temperature of the Reactants, Presence of a Catalyst, Pressure factor
Rate of reaction is the pace at which the products of a chemical reaction are created from the reactants. It provides some information about the time frame in which a reaction can be accomplished. For example, the reaction rate of cellulose combustion in fire is extremely high, and the reaction is finished in less than a second.
What is Reaction Rate?
The rate of reaction, often known as the reaction rate, refers to the pace at which reactants are converted into products. When we talk about chemical processes, we know that the rate at which they occur varies greatly.
Some chemical reactions are virtually instantaneous, while others take time to achieve their final equilibrium. The rate of a reaction, according to the general definition, is the rate at which a reaction occurs.
Wood combustion, for example, has a high reaction rate because the process is fast, whereas iron rusting has a low reaction rate since the process is sluggish.
Table of Contents
Factors Affecting the Rate of Reaction
Chemical reactions occur only when reactant molecules clash with one another. The Collision hypothesis of Chemical Kinetics describes this. According to the collision, for a reaction to occur, the reactants must collide with sufficient energy that is greater than the activation energy Ea. However, other factors can affect the rate of reaction, such as increasing the fraction of molecules with energies greater than the activation energy Ea. The rate of a reaction is influenced by four elements. They are as follows:
Nature of the Reactant
Chemical reactions occur almost instantly in an aqueous solution. Because the chemical bonds of reactant molecules are broken down. The ions’ attractive forces are disrupted, and the ions are hydrated by the water molecules. Furthermore, most ions have equal attractive forces in all directions. In most circumstances, no covalent connections must be disrupted in these situations. Reactions between molecules that require covalent bonds to be broken, on the other hand, tend to be very sluggish. As a result, the pace of reaction is influenced by the structural properties of the reactant molecules, such as bond polarity, geometry, overall size, and orientation.
Concentration of the Reactants
We know that the rate of most reactions increases as the concentration of the reactants increases. Increasing a reactant’s concentration means increasing the number of reactant molecules in the same volume. For many (but not all) reactions, there is a direct link between concentration and rate of reaction. As a result, when the concentration doubles, the rate of reaction doubles as well. This is explained by the collision hypothesis, which states that doubling the number of reactant molecules results in twice as many collisions occurring at the same time.
Temperature of the Reactants
In almost all circumstances, the rate of a reaction increases as the temperature rises. The pace of reaction doubles per 10° increase in temperature! This is a really strong effect. For example, a temperature increase from 20° to 80° (six 10° increments) will result in a reaction rate that is 26 = 64 times faster. That is a significant rate change. The Collision theory can also explain this: the average kinetic energy of all molecules is a direct function of temperature. Because the molecules collide with more energy, their activation energy lowers.
Presence of a Catalyst
A catalyst is a chemical that speeds up a reaction without really participating in it. Catalysts work by giving an alternative chemical pathway. It is the one that uses the least amount of energy to transform the reactants into products. Some catalysts accelerate more than one sort of reaction, but others, such as enzymes in our cells, are specific to a particular reaction or even a single type of reactant molecule. As a result, a catalyst accelerates the process.
Pressure factor
The concentration of gases increases as pressure increases, increasing the rate of reaction. The reaction rate accelerates in the direction of fewer gaseous molecules and slows in the opposite direction. As a result, it is clear that pressure and concentration are related and that they both influence the rate of response.
Sample Questions (FAQs)
Question 1: How does concentration affect the rate of reaction?
Answer:
Collision theory states that increasing the number of reactant molecules increases the number of collisions that occur for a reaction to occur. Similarly, raising the concentration, or the amount of reactant molecules in the solution, will increase the number of collisions that occur in the solution. As a result, the rate of the reaction will accelerate.
Question 2: What is the difference between the chemical kinetics of the reaction and the chemical balancing of the equation?
Answer:
The chemical kinetics of the reaction provides information on the mechanism and pace of the reaction, whereas a balanced chemical equation provides information about the stoichiometry of the reaction.
Question 3: Why does the reaction rate increase with increasing temperature?
Answer:
As the temperature of the reaction rises, the average kinetic energy of the ions and molecules rises as collisions between the ions and molecules become more frequent.
Question 4: What is the difference between chemical thermodynamics and chemical kinetics?
Answer:
Chemical kinetics, often known as reaction kinetics, is concerned with the investigation of reaction rates. Chemical thermodynamics is the study of the interaction of heat and work with chemical processes or physical state changes within the limitations of thermodynamic rules.
Question 5: How do Catalysts speed up reactions?
Answer:
The catalyst speeds up the reaction by allowing a novel reaction pathway to occur at a lower activation energy. It does not consume in the process and also does not alter in chemical properties.
Neeraj Anand, Param Anand
Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations.
In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS".
He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.
Below is the CBSE Class 12 Syllabus along with the marking scheme and time duration of the Chemistry exam.
S.No
Title
No. of Periods
Marks
1
Solutions
10
7
2
Electrochemistry
12
9
3
Chemical Kinetics
10
7
4
d -and f -Block Elements
12
7
5
Coordination Compounds
12
7
6
Haloalkanes and Haloarenes
10
6
7
Alcohols, Phenols and Ethers
10
6
8
Aldehydes, Ketones and Carboxylic Acids
10
8
9
Amines
10
6
10
Biomolecules
12
7
Total
70
CBSE Class 12 Chemistry Practical Syllabus along with Marking Scheme
The following is a breakdown of the marks for practical, project work, class records, and viva. The total number of marks for all parts is 15. The marks for both terms are provided in the table below.
Evaluation Scheme for Examination
Marks
Volumetric Analysis
08
Salt Analysis
08
Content-Based Experiment
06
Project Work and Viva
04
Class record and Viva
04
Total
30
CBSE Class 12 Chemistry Syllabus (Chapter-wise)
Unit -1: Solutions
Raoult's law.
Colligative properties - relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure, determination of molecular masses using colligative properties, abnormal molecular mass.
Solutions, Types of solutions, expression of concentration of solutions of solids in liquids, solubility of gases in liquids, solid solutions.
Van't Hoff factor.
Unit -2: Electrochemistry
Redox reactions, EMF of a cell, standard electrode potential
Nernst equation and its application to chemical cells
Relation between Gibbs energy change and EMF of a cell
Kohlrausch's Law
Electrolysis and law of electrolysis (elementary idea)
Dry cell-electrolytic cells and Galvanic cells
Conductance in electrolytic solutions, specific and molar conductivity, variations of conductivity with concentration.
Lead accumulator
Fuel cells
Unit -3: Chemical Kinetics
Rate of a reaction (Average and instantaneous)
Rate law and specific rate constant
Integrated rate equations and half-life (only for zerfirst-order order reactions)
Concept of collision theory (elementary idea, no mathematical treatment)
Factors affecting rate of reaction: concentration, temperature, catalyst;
Order and molecularity of a reaction
Activation energy
Arrhenius equation
Unit -4: d and f Block Elements
Lanthanoids- Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences.
Actinoids- Electronic configuration, oxidation states and comparison with lanthanoids.
General introduction, electronic configuration, occurrence and characteristics of transition metals, general trends in properties of the first-row transition metals – metallic character, ionization enthalpy, oxidation states, ionic radii, color, catalytic property, magnetic properties, interstitial compounds, alloy formation, preparation and properties of K2Cr2O7 and KMnO4.
Unit -5: Coordination Compounds
Coordination compounds - Introduction, ligands, coordination number, color, magnetic properties and shapes
The importance of coordination compounds (in qualitative analysis, extraction of metals and biological system).
IUPAC nomenclature of mononuclear coordination compounds.
Bonding
Werner's theory, VBT, and CFT; structure and stereoisomerism
Unit -6: Haloalkanes and Haloarenes
Haloarenes: Nature of C–X bond, substitution reactions (Directive influence of halogen in monosubstituted compounds only). Uses and environmental effects of - dichloromethane, trichloro methane, tetrachloromethane, iodoform, freons, DDT.
Haloalkanes: Nomenclature, nature of C–X bond, physical and chemical properties, optical rotation mechanism of substitution reactions.
Unit -7: Alcohols, Phenols and Ethers
Phenols: Nomenclature, methods of preparation, physical and chemical properties, acidic nature of phenol, electrophilic substitution reactions, uses of phenols.
Ethers: Nomenclature, methods of preparation, physical and chemical properties, uses.
Alcohols: Nomenclature, methods of preparation, physical and chemical properties (of primary alcohols only), identification of primary, secondary and tertiary alcohols, mechanism of dehydration, and uses with special reference to methanol and ethanol.
Unit -8: Aldehydes, Ketones and Carboxylic Acids
Carboxylic Acids: Nomenclature, acidic nature, methods of preparation, physical and chemical properties; uses.
Aldehydes and Ketones: Nomenclature, nature of carbonyl group, methods of preparation, physical and chemical properties, mechanism of nucleophilic addition, the reactivity of alpha hydrogen in aldehydes, uses.
Unit -9: Amines
Diazonium salts: Preparation, chemical reactions and importance in synthetic organic chemistry.
Amines: Nomenclature, classification, structure, methods of preparation, physical and chemical properties, uses, and identification of primary, secondary and tertiary amines.
Unit -10: Biomolecules
Proteins -Elementary idea of - amino acids, peptide bond, polypeptides, proteins, structure of proteins - primary, secondary, tertiary structure and quaternary structures (qualitative idea only), denaturation of proteins; enzymes. Hormones - Elementary idea excluding structure.
Vitamins - Classification and functions.
Carbohydrates - Classification (aldoses and ketoses), monosaccharides (glucose and fructose), D-L configuration oligosaccharides (sucrose, lactose, maltose), polysaccharides (starch, cellulose, glycogen); Importance of carbohydrates.
Nucleic Acids: DNA and RNA.
The syllabus is divided into three parts: Part A, Part B, and Part C. Part A consist of Basic Concepts of Chemistry, which covers topics such as atomic structure, chemical bonding, states of matter, and thermochemistry. Part B consists of Topics in Physical Chemistry, which includes topics such as chemical kinetics, equilibrium, and electrochemistry. Part C consists of Topics in Organic Chemistry, which covers topics such as alkanes, alkenes, alkynes, and aromatic compounds.
Basic Concepts of Chemistry:
Atomic structure: This section covers the fundamental concepts of atomic structure, including the electronic configuration of atoms, the Bohr model of the atom, and the wave nature of matter.
Chemical bonding: This section covers the different types of chemical bonds, including ionic, covalent, and metallic bonds, as well as the concept of hybridization.
States of the matter: This section covers the three states of matter - solid, liquid, and gas - and the factors that influence their properties.
Thermochemistry: This section covers the principles of thermochemistry, including the laws of thermodynamics and the concept of enthalpy.
Chapters in Physical Chemistry:
Chemical kinetics: This section covers the study of the rate of chemical reactions and the factors that influence it, including the concentration of reactants, temperature, and the presence of catalysts.
Equilibrium: This section covers the principles of chemical equilibrium, including the concept of Le Chatelier's principle and the equilibrium constant.
Electrochemistry: This section covers the principles of electrochemistry, including the concept of half-cell reactions, galvanic cells, and electrolysis.
Chapters in Organic Chemistry:
Alkanes: This section covers the properties and reactions of alkanes, including their structure, isomerism, and combustion.
Alkenes: This section covers the properties and reactions of alkenes, including their structure, isomerism, and addition reactions.
Alkynes: This section covers the properties and reactions of alkynes, including their structure, isomerism, and addition reactions.
Aromatic compounds: This section covers the properties and reactions of aromatic compounds, including their structure, isomerism, and electrophilic substitution reactions.
In addition to the topics covered in the syllabus, the CBSE Class 12 Chemistry exam also tests students on their analytical and problem-solving skills, as well as their ability to apply the concepts learned in the classroom to real-world situations.
Students can also check out the Tips for the Class 12 Chemistry Exam. They can easily access the Class 12 study material in one place by visiting the CBSE Class 12 page at ANAND CLASSES (A School Of Competitions). Moreover, to get interactive lessons and study videos, download the ANAND CLASSES (A School Of Competitions) App.
Frequently Asked Questions on CBSE Class 12 Chemistry Syllabus
Q1
How many chapters are there in the CBSE Class 12 Chemistry as per the syllabus?
There are 10 chapters in the CBSE Class 12 Chemistry as per Syllabus. Students can learn all these chapters efficiently using the study materials provided at ANAND CLASSES (A School Of Competitions).
Q2
What is the marking scheme for CBSE Class 12 Chemistry practical exam according to the syllabus?
The marking scheme for CBSE Class 12 Chemistry practical exam, according to the syllabus, is 8 marks for volumetric analysis, 8 marks for salt analysis, 6 marks for the content-based experiment, 4 marks for the project and viva and 4 marks for class record and viva.
Q3
Which is the scoring chapter in Chemistry as per CBSE Class 12 syllabus?
The chapter Electrochemistry in Chemistry is the scoring chapter as per CBSE Class 12 syllabus.
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