A Complete Guide to Lab Manual for Class 11 Chemistry NCERT
Lab Manual for Class 11 Chemistry NCERT
Chemistry is a fascinating subject that involves the study of matter and its interactions with other substances. It is also a practical subject that requires hands-on experience in the laboratory to understand the concepts and principles better. In this article, we will explore the lab manual for class 11 chemistry NCERT, which is a comprehensive guide for students to perform various experiments and activities in the chemistry lab.
Lab Manual For Class 11 Chemistry Ncert
Basic Laboratory Techniques
Before we dive into the specific experiments, let us first review some basic laboratory techniques that are essential for any chemistry student. These techniques include measuring mass and volume, using a burette and a pipette, preparing standard solutions, and performing titrations.
Measuring mass and volume
Mass is the amount of matter in an object, and volume is the amount of space occupied by an object. To measure mass, we use a balance, which compares the mass of an object with a known mass. To measure volume, we use a measuring cylinder, which has a graduated scale that indicates the volume of liquid in it.
Using a burette and a pipette
A burette is a long glass tube with a tap at the bottom and a scale on the side. It is used to deliver a precise volume of liquid from one container to another. A pipette is a slender glass tube with a bulb at one end and a narrow tip at the other. It is used to transfer a fixed volume of liquid from one container to another.
Preparing standard solutions
A standard solution is a solution whose concentration is known accurately. It is prepared by dissolving a known mass of solute in a known volume of solvent. The concentration of a standard solution can be expressed in different units, such as molarity (M), molality (m), normality (N), or percentage (%).
A titration is a technique that involves adding a standard solution to an unknown solution until a chemical reaction is complete. The point at which the reaction is complete is called the end point, which can be detected by using an indicator or a pH meter. The amount of standard solution added to reach the end point is called the titre value, which can be used to calculate the concentration or amount of substance in the unknown solution.
Characterization and Purification of Chemical Substances
In this section, we will learn how to characterize and purify chemical substances by using different methods, such as crystallization, melting point determination, boiling point determination, and chromatography.
Crystallization is a process that involves separating a solid substance from its impurities by dissolving it in a suitable solvent and then cooling the solution to form crystals. The crystals are then filtered, washed, and dried. The purity of the crystals can be checked by their shape, size, color, and transparency.
Melting point determination
Melting point is the temperature at which a solid substance changes into a liquid state. It is a characteristic property of a pure substance and can be used to identify it. To determine the melting point of a substance, we use a melting point apparatus, which consists of a capillary tube, a thermometer, and a heating device. The substance is packed in the capillary tube and placed in the heating device along with the thermometer. The temperature is gradually increased until the substance melts completely. The temperature at which the substance starts to melt and the temperature at which it completely melts are recorded as the melting point range.
Boiling point determination
Boiling point is the temperature at which a liquid substance changes into a gaseous state. It is also a characteristic property of a pure substance and can be used to identify it. To determine the boiling point of a substance, we use a boiling point apparatus, which consists of a round-bottomed flask, a thermometer, and a heating device. The substance is placed in the flask and heated until it boils. The temperature at which the substance boils is recorded as the boiling point.
Chromatography is a technique that involves separating a mixture of substances based on their different affinities for two phases: a stationary phase and a mobile phase. The stationary phase can be a solid or a liquid, and the mobile phase can be a liquid or a gas. The mixture is applied on the stationary phase and then the mobile phase is passed through it. The substances in the mixture move along with the mobile phase at different rates depending on their attraction for the stationary phase. The separation of the substances can be observed by their different positions or colors on the stationary phase.
Experiments Related to pH Change
In this section, we will learn how to perform experiments related to pH change, such as using indicators, studying the pH of different solutions, effect of dilution on pH, and buffer solutions.
An indicator is a substance that changes its color depending on the acidity or basicity of a solution. It can be used to determine whether a solution is acidic, basic, or neutral. Some common indicators are litmus paper, phenolphthalein, methyl orange, and universal indicator.
Studying the pH of different solutions
pH is a measure of how acidic or basic a solution is. It is defined as the negative logarithm of the hydrogen ion concentration in moles per liter. The pH scale ranges from 0 to 14, where 7 is neutral, below 7 is acidic, and above 7 is basic. To study the pH of different solutions, we can use indicators or pH meters.
Effect of dilution on pH
Dilution is the process of adding more solvent to a solution to decrease its concentration. When we dilute an acidic or basic solution with water, we decrease the number of hydrogen ions or hydroxide ions per unit volume, respectively. This affects the pH of the solution depending on whether it is a strong acid or base, or a weak acid or base.
A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added to it. It usually consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. A buffer solution maintains its pH by neutralizing any excess acid or base added to it.
In this section, we will learn how to perform experiments related to chemical equilibrium, such as Le Chatelier's principle, common ion effect, and solubility product.
Le Chatelier's principle
Le Chatelier's principle states that when a system at equilibrium is subjected to a change in concentration, temperature, or pressure, it shifts its equilibrium position to counteract the change and restore equilibrium. For example, if we increase the concentration of reactants in an equilibrium reaction, the system will shift towards the products to decrease the concentration of reactants.
Common ion effect
Common ion effect
The common ion effect is the phenomenon that occurs when two solutions containing ions in common are mixed together and affect each other's solubility or degree of ionization. For example, if we add sodium acetate (NaCH3COO) to acetic acid (CH3COOH), we will increase the concentration of acetate ions (CH3COO) in the solution. This will shift the equilibrium of the weak acid to the left, reducing its ionization and lowering its pH.
Solubility product is a constant that represents the product of the concentrations of the ions of a sparingly soluble salt in a saturated solution at a given temperature. It is denoted by Ksp. For example, the solubility product of silver chloride (AgCl) is given by Ksp = [Ag][Cl], where [Ag] and [Cl] are the concentrations of silver and chloride ions in moles per liter. The solubility product can be used to calculate the solubility of a salt or to predict whether a precipitation reaction will occur or not.
In this section, we will learn how to perform salt analysis, which is a systematic method of identifying the cations and anions present in a given salt. Salt analysis involves two steps: preliminary tests and confirmatory tests.
Preliminary tests are simple tests that give us some clues about the nature and composition of the salt. They include physical appearance, solubility, flame test, action of heat, action of dilute acids, and action of concentrated acids.
Confirmatory tests for cations and anions
Confirmatory tests are specific tests that confirm the presence or absence of a particular ion in the salt. They are based on the formation of characteristic precipitates, colors, odors, or gases when a suitable reagent is added to the salt solution. For example, to confirm the presence of lead (Pb) ion in a salt, we can add potassium iodide (KI) solution to it and observe a yellow precipitate of lead iodide (PbI2). To confirm the presence of sulphate (SO4) ion in a salt, we can add barium chloride (BaCl2) solution to it and observe a white precipitate of barium sulphate (BaSO4).
Organic Chemistry Experiments
In this section, we will learn how to perform organic chemistry experiments, such as detection of elements in organic compounds and functional group tests.
Detection of elements in organic compounds
To detect the presence of carbon (C), hydrogen (H), nitrogen (N), sulphur (S), and halogens (F, Cl, Br, I) in an organic compound, we can use different methods, such as Lassaigne's test, sodium fusion test, sodium extract test, or carius method.
Functional group tests
A functional group is a specific group of atoms or bonds that determines the chemical properties and reactions of an organic compound. Some common functional groups are alcohols (-OH), aldehydes (-CHO), ketones (>C=O), carboxylic acids (-COOH), esters (-COO-), amines (-NH2), amides (-CONH2), etc. To identify the functional group present in an organic compound, we can use different reagents that react with it and produce characteristic changes in color, odor, or precipitate. For example, to test for aldehydes, we can use Fehling's solution or Tollens' reagent. To test for carboxylic acids, we can use sodium bicarbonate or litmus paper.
In this article, we have discussed the lab manual for class 11 chemistry NCERT, which covers various topics and experiments related to chemistry. We have learned about the basic laboratory techniques, the characterization and purification of chemical substances, the experiments related to pH change, the chemical equilibrium, the salt analysis, and the organic chemistry experiments. We have also seen how to use different indicators, reagents, and apparatus to perform these experiments and observe the results. We hope that this article has helped you to understand the lab manual better and to prepare for your practical exams.
Q1: What is the difference between a standard solution and a normal solution?
A1: A standard solution is a solution whose concentration is known accurately, while a normal solution is a solution whose concentration is expressed in terms of normality (N), which is the number of gram equivalent weights of solute per liter of solution.
Q2: What is the difference between a melting point and a freezing point?
A2: A melting point is the temperature at which a solid substance changes into a liquid state, while a freezing point is the temperature at which a liquid substance changes into a solid state. For pure substances, the melting point and the freezing point are the same.
Q3: What is the difference between an acid and a base?
A3: An acid is a substance that releases hydrogen ions (H) or hydronium ions (H3O) in water, while a base is a substance that releases hydroxide ions (OH) in water. An acid has a pH below 7, while a base has a pH above 7.
Q4: What is the difference between a reversible reaction and an irreversible reaction?
A4: A reversible reaction is a reaction that can proceed in both directions, i.e., from reactants to products and from products to reactants. An irreversible reaction is a reaction that can proceed in only one direction, i.e., from reactants to products. A reversible reaction can reach a state of equilibrium, while an irreversible reaction cannot.
Q5: What is the difference between an organic compound and an inorganic compound?
A5: An organic compound is a compound that contains carbon atoms bonded to other carbon atoms or to hydrogen atoms, usually with some other elements such as oxygen, nitrogen, sulphur, or halogens. An inorganic compound is a compound that does not contain carbon atoms bonded to other carbon atoms or to hydrogen atoms, except for some exceptions such as carbon dioxide, carbon monoxide, carbonates, etc. 71b2f0854b