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Chemistry 12

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Biomolecules

1. Biomolecules: Macromolecules which are naturally occurring in biological systems are called biomolecules. Examples: polysaccharides (starch, cellulose, etc.), proteins, enzymes, vitamins, hormones, etc. 2. Carbohydrates: These are optically active polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis, e.g ., glucose, sucrose, cellulose, starch, etc. 3. Classification of carbohydrates: ( a ) Monosaccharides: The simple carbohydrates that cannot be broken further into smaller units on hydrolysis, e.g. , glucose and fructose, ribose, etc. ( b ) Oligosaccharides: These are the carbohydrates which on hydrolysis give two to ten units of monosaccharides, e.g ., sucrose, maltose, raffinose, stachyose, etc. ( c ) Polysaccharides: These are the carbohydrates which produce a large number of monosaccharide units on hydrolysis, e.g ., starch, cellulose, etc. Importance of carbohydrates: ( i ) C...

Wave optics

1. Wave Nature of Light: Huygen’s Theory There are some phenomena like interference, diffraction and polarisation which could not be explained by Newton’s corpuscular theory. These were explained by wave theory first proposed by Huygen. The assumptions of Huygen’s wave theory are: ( i ) A source sends waves in all possible directions. The locus of particles of a medium vibrating in the same phase is called a wavefront. For a point source, the wavefront is spherical; while for a line source the wavefront is cylindrical. A distant wavefront is plane. ( ii ) Each point of a wavefront acts as a source of secondary wavelets. The envelope of all wavelets at a given instant gives the position of a new wavefront. 2. Wavefront A wavefront is defined as the locus of all the particles which are vibrating in the same phase. The perpendicular line drawn at any point on the wavefront represents the direction of propagation of the wave at that point and is called the ‘ ray ’....

D & F Block

1. d -Block Elements: The d -block elements are those elements in which the last electron enters the d –subshell of penultimate shell. The general electronic configuration of these elements is ( n – 1) d 1–10 ns 1–2 , where n is outermost shell. The d -block consisting of groups 3–12 occupies the large middle section of the periodic table. 2. Transition Elements: The elements of d -block are known as transition elements as they possess properties that are transitional between the s and p block elements. A transition element is defined as an element which has incompletely filled d -orbitals in its ground state or any one of its oxidation states. There are four series of transition elements spread between group 3 and 12. First transition series or 3 d -series: Scandium ( 21 Sc) to Zinc ( 30 Zn) Second transition series or 4 d -series: Yttrium ( 39 Y) to Cad...

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Chemistry 12

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