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Before going to take that test you need to prepare that chapter. To help in your preparation we have added classroom pdf notes of Some basic Concepts of Chemistry chapter. This is one of the most important chpaters of chemistry. This is the most basic chapter of chemistry. Without studying mole concept it is impossible to learn chemistry. In these notes we have covered all the topics of mole concepts.
To give you a quick glance of the chapter. But, if otherwise, the terminal zeros are not significant if there is no decimal point. For example, has only one significant figure, but Such numbers are better represented in scientific notation. We can express the number for one significant figure for two significant figures and for three significant figures. Law of Conservation of Mass. Antoine Lavoisier established the Law of Conservation of Mass.
It states that matter can neither be created nor destroyed. Law of Definite Proportions states that a given compound always contains exactly the same proportion of elements by weight. Law of Multiple Proportions states that if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in the ratio of small whole numbers.
He observed that when gases combine or are produced in a chemical reaction they do so in a simple ratio by volume provided all gases are at same temperature and pressure. In , Avogadro proposed that equal volumes of gases at the same temperature and pressure should contain equal number of molecules.
Atoms of different elements differ in mass. These are neither created nor destroyed in a chemical reaction. One atomic mass unit is defined as a mass exactly equal to one twelfth the mass of one carbon — 12 atom.
Molecular mass is the sum of atomic masses of the elements present in a molecule. It is obtained by multiplying the atomic mass of each element by the number of its atoms and addingthem together.
Molecular mass expressed in grams is called gram molecular mass Formula Mass: Sum of atomic masses of all atoms in a formula unit of the compound.
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. This number of entities in 1 mol is so important that it is given a separate name and symbol.
An empirical formula represents the simplest whole number ratio of various atoms present in a compound whereas the molecular formula shows the exact number of different types of atoms present in a molecule of a compound. Molecular formula shows the exact number of different types of atoms present in a molecule of a compound.
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