CBSE Class 12 Sample Papers, Syllabus, Test Papers & NCERT Solutions

1. Chemicals play a very important role in improving the quality of human life. Many substances which are used in our daily life situations are chemical compounds. 2. Drugs are chemicals of low molecular masses (-100- 500 u). These interacts with macromolecular targets and produce a biological response. 3. If taken in doses higher than those recommended, most of the […]

1. A polymer is a large molecule of high molecular mass formed by the repetitive bonding of many small molecules called monomers. The process by which the monomers are transformed into polymers is called polymerisation. As polymers are single big size molecules, they are also called  macromolecules. 2. Classification of polymers on the basis of source: (a) Natural polymers: Proteins, […]

1. Carbohydrates is a class of compounds that include polyhydric aldehydes and ketones and large number of other polymeric molecules that yield these on hydrolysis, e.g., sugars, glycogen, cellulose, starch, etc. 2. Depending upon their behaviour on hydrolysis, carbohydrates are further divided into three types: Monosaccharides (e.g., glucose, fructose etc.), disaccharides (e.g., sucrose, maltose etc.) and polysaccharides […]

1. Amines are the derivatives of ammonia in which one or more hydrogen atoms have been replaced by alkyl groups. 2. Amines are classified as primary, secondary, or tertiary according as one, two or three hydrogen atoms in the ammonia molecule have been substituted by alkyl groups. 3. Preparation of amines: (i) By reduction of nitro compounds. (ii) An […]

1. The classes of organic compounds containing carbonyl group (CO) as the functional group are aldehydes, ketones, carboxylic acids and their derivates. These are collectively called carbonyl compounds. 2. Nature of carbonyl group: Oxygen atom in carbonyl group is far more electronegative than carbon atom. As a result, the oxygen atom tends to attract the electron cloud […]

1. Alcohols and phenols may be classified as monohydric, dihydric, trihydric or polyhydric according to number of hydroxyl groups they contain one, two, three or many respectively in their molecules. 2. Primary (1°), secondary (2°) and tertiary (3°) alcohols are those in which as the OH group is attached to a primary, secondary and tertiary carbon atoms […]

1. Haloalkanes are classified as fluoro, chloro, bromo or iodo compounds according to the type of halogen present and as mono-, di- tri-, tetra- haloalkanes, etc., according to the one, two, three, four, etc., halogen atoms respectively present in their molecule. 2. Alkyl halides are further classified as primary (1°), secondary (2°) and tertiary (3°) according to […]

1. Coordination compounds contain a central atom (or cation) which is coordinated to a suitable number of anions or neutral molecules and usually retain their identity in solution as well as in solid state. These may be a positively charged, negatively charged or a neutral species, [Co(NH3)6]3+, [NiCl4]2-, [Ni(CO)4] etc. 2. In 1893, Werner proposed a theory […]

1. The elements lying in the middle of Periodic Table between s-block and p-block elements (i.e between group 2 and 13) are known as d-block or transition elements. 2. There are three transition series each of 10 elements: (i) First transition series: It involves filling of 3d-orbitals. It starts from scandium (Z = 21) and goes upto zinc (Z […]

I Group 15 Elements: The Nitrogen Family 1. In group 15 of the Periodic Table, the elements, nitrogen (7N), phosphorus (15P), arsenic (33As), antimony (51Sb) and bismuth (83Bi) are present. 2. (a) The elements of this group can exhibit various oxidation states ranging between -3 to+ 5. (b) Maximum covalency of Nitrogen is four because it does […]

1. Minerals: The natural substance in which the metals or their compounds occur in the earth is called minerals. 2. Ores: The minerals from which the metals can be conveniently and economically extracted are called ores. 3. Native ores: These ores contain metals in the free state, e.g., silver, gold, platinum, etc. 4. Metallurgy: The whole process of obtaining […]

1. This phenomenon of attracting and retaining the molecules of a substance by a solid (or a liquid) on its surface resulting into a higher concentration of the molecules on the surface is known as adsorption. 2. The substance that is adsorbed is called adsorbate and the substance which adsorbs is called adsorbent. 3. Desorption is a process of removing an adsorbed substance […]

1. Chemical kinetics is the branch of chemistry which deals with the study of rates (or fastness) of chemical reactions, the factors affecting it and the mechanism by which the reactions proceed. 2. Rate of reaction is the change in concentration of reactants or products per unit time. For a general reaction, A+B –> C The rate […]

1. Electrochemistry is the branch of chemistry which deals with the relationship between electrical energy and chemical energy and inter-conversion of one form into another. 2. An electrochemical cell consists of two metallic electrodes dipped in electrolytic solutions. The cells are of two types: (a) Electrolytic cells (b) Galvanic cells 3. A galvanic cell consists of two half […]

1. A solution is a homogeneous mixture of two or 9. more chemically non-reacting substances. The components of a solution generally cannot be separated by filtration, settling or centrifuging. 2. A solution may be classified as solid, liquid or a gaseous solution. 3. Solubility is defined as the amount of solute in a saturated solution per 100g of […]

1. Solids are substances which have fixed shape and volume. 1’hey are characterised by rigidity, incompressibility, slow diffusion and mechanical strength. They are classified as: (a) Crystalline solids (b) Amorphous solids . 2. The crystalline solids are further classified as: (a) Metallic solids (b) Ionic solids (c) Covalent solids (d) Molecular solids 3. A regular three dimensional arrangement […]