(a) Law of conservation of mass : "In all physical and chemical changes, the total mass of the reactants is equal to that of the products" or "matter can neither be created nor destroyed." (b) Law of constant composition/definite proportion : "A chemical compound is always found to be made up of the same elements combined together in the same fixed ratio by weight". (c) Law of multiple proportions : "When two elements combine together to form two or more chemical compounds, then the weight of one of the elements which combine with a fixed weight of the other bear a simple ratio to one another". (d) Law of reciprocal proportions : The ratio of the weights of two elements A and B which combine with a fixed weight of the third element C is either the same or a simple multiple of the ratio of the weights of A and B which directly combine with each other.  (e) Gay-Lussac's law of gaseous volumes : "When gases react together, they always do so...

 The four main branches of chemistry are: (1) Organic chemistry;          (2) Inorganic chemistry; (3) Physical chemistry;         (4) Analytical chemistry. (1) Organic chemistry : It is concerned with the study of  compounds of carbon except carbonates, bicarbonates, cyanides,  isocyanides, carbides and oxides of carbon. It is actually the  study of hydrocarbons and their derivatives. (2) Inorganic chemistry : It deals with the study of all  known elements and their compounds except organic  compounds. It is concerned with the materials obtained from  minerals, air, sea and soil. (3) Physical chemistry : It is concerned with the physical  properties and constitution of matter, the laws of chemical  combination and theories governing reactions. The effect of  temperature, pressure, light, concentration, etc., on reactions  come under the scope of physical chemistry. (4) Analytical ...

Gold number of a protective colloid is the minimum weight of it in  milligrams which must be added to 10 mL of a substance (red gold sol)  so that no coagulation of the gold sol takes place when 1 mL of 10%  sodium chloride solution is rapidly added to it. or Weight of the dried protective agent in milligrams, which, when added  to 10 mL of a standard gold sol (0.0053 to 0.0058%), is just sufficient to  prevent a colour change from red to blue on the addition of 1 mL of 10%  sodium chloride solution, is equal to the gold number of protective  colloid.  Protective power ∝ 1/Gold number Note: Gold number is a practical value, it cannot be obtained  theoretically.

 (A) Every scientific observation involves some degree of uncertainty depending upon the limitation of instrument. To represent scientific data, role of significant figures has its own importance.  (B) Significant figures are equal to the number of digits in numbers with last digit uncertain and rest all are certain digits i.e. all the digits of datum including the uncertain one , are called significant figures.  (C) Rules for determination of significant figure:  (i) All non zero digits are significant.  Example : 3.14 has three significant figures  (ii) The zeros to the right of the decimal point are significant.  Example : 3.0 has two significant figures.  (iii) The zeros to the left of the first non zero digit in a number are not significant.  Example : 0.02 has one significant figure.  (iv) The zeros between two non zero digits are also significant.  Example : 6.01 has three significant figures.  (v) Exponential form : N...

USE THIS HANDOUT TO PRACTICE AND IMPROVE YOUR UNDERSTANDING OF IUPAC NOMENCLATURE OF ORGANIC COMPOUNDS. VISIT THE LINK FOR VIDEO ON THE TOPIC: IUPAC NOMENCLATURE VISIT THE LINK FOR THE HANDOUT: HANDOUT