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Extrascore Sample Questions - Answers Q.1: What are the µlaws of chemical combination¶? Ans: There are two important laws of chemical combination established by Lavoisier,are as follows: (i) Law of Conservation of Mass The law of conservation of mass states that mass can neither be created nor destroyedin a chemical reaction.(ii) Law of Constant Proportions The Law of Constant Proportions which is also known as the Law of DefiniteProportions, was established by Proust. According to this law, in a chemical substancethe elements are always present in definite proportion by mass. All pure samples of acompound contain the same elements combined together in the same proportion bymass. For example, a sample of water would always contain hydrogen and oxygen inthe ratio of 1:8 by mass irrespective of the source of water Q.4: What are the postulates of Dalton¶s Atomic Theory of matter ? Ans: According to Dalton¶s atomic theory, all matter, whether an element, a compoundor a mixture is composed of small particles called atoms. The different postulates of Dalton¶s atomic theory are stated as follows: (1) All matter is made of very tiny particles called atoms. (2) Atoms are indivisible particles, which can not be created or destroyed in a chemicalreaction. (3) Atoms of a given element are identical in mass and chemical properties. (4) Atoms of different elements have different masses and chemical properties. (5) Atoms combine in the ratio of small whole numbers to form compounds. (6) The relative number and kinds of atoms are constant in a given compound.Q.5: What is the full form of IUPAC? What is the present accepted norm of IUPAC for naming symbols of elements? Ans: The full name of IUPAC is International Union of Pure and Applied Chemistry.Many of the symbols are the first one or two letters of the element¶s name in English.The first letter of a symbol is always written as a capital letter (upper case) and
Extrascore Sample Questions - Answers Q.1: What are the µlaws of chemical combination¶? Ans: There are two important laws of chemical combination established by Lavoisier,are as follows: (i) Law of Conservation of Mass The law of conservation of mass states that mass can neither be created nor destroyedin a chemical reaction.(ii) Law of Constant Proportions The Law of Constant Proportions which is also known as the Law of DefiniteProportions, was established by Proust. According to this law, in a chemical substancethe elements are always present in definite proportion by mass. All pure samples of acompound contain the same elements combined together in the same proportion bymass. For example, a sample of water would always contain hydrogen and oxygen inthe ratio of 1:8 by mass irrespective of the source of water Q.4: What are the postulates of Dalton¶s Atomic Theory of matter ? Ans: According to Dalton¶s atomic theory, all matter, whether an element, a compoundor a mixture is composed of small particles called atoms. The different postulates of Dalton¶s atomic theory are stated as follows: (1) All matter is made of very tiny particles called atoms. (2) Atoms are indivisible particles, which can not be created or destroyed in a chemicalreaction. (3) Atoms of a given element are identical in mass and chemical properties. (4) Atoms of different elements have different masses and chemical properties. (5) Atoms combine in the ratio of small whole numbers to form compounds. (6) The relative number and kinds of atoms are constant in a given compound.Q.5: What is the full form of IUPAC? What is the present accepted norm of IUPAC for naming symbols of elements? Ans: The full name of IUPAC is International Union of Pure and Applied Chemistry.Many of the symbols are the first one or two letters of the element¶s name in English.The first letter of a symbol is always written as a capital letter (upper case) and