Introduction
Chemistry is a branch of science which deals with study of matter and various changes it undergoes. It deals with the preparation, properties, reactions and structures of chemical elements and compounds. For convenience the study of chemistry is sub-divided into various branches such as:
(i) Inorganic chemistry (ii) Organic chemistry (iii) Physical chemistry
(iv) Analytical chemistry (v) Industrial chemistry
During the formation of molecules of compounds, atoms combine in certain fixed proportions. This is because of the fact that different atoms have different combining capacities. The combining capacity of an atom or radical is known as its valency.
In addition to atoms and molecules, a third type of particles occurs in substances. These particles, called ions, or atoms or group of atoms that carry an electrical charge. An ion is formed when electrons are removed from or added to an atoms or group of atoms. When electrons is/are removed the resulting ion is called a cation or basic radical. A cation is positively charged ion. (e.g\[N{{a}^{+}}\]. When electron is/are added the resulting ion is called an anion or acidic radicals. An anion is negatively charged ion e.g.,\[(C{{l}^{-}},O_{2}^{2-})\]An ion or radical is classified as monovalent, divalent, trivalent or tetravalent when the number of charges over it is 1,2,3 or 4 respectively.
- Formula of Elements and Compounds
Formula of dements: The molecule of an element is denoted by writing the symbol of the element and, to the right and below it, a number expressing the number of atoms in the molecule.
Formula of compound: A molecule of a compound maybe made up of atom of different elements linked up together chemically and in definite proportion by weight.
- Chemical formula: It is of two types:
(i) Molecular formulae: Chemical formulae that indicate the actual number and type of atoms in a molecule is called molecular formulae.
(ii) Empirical formulae: Chemical formulae that indicate only the relative number of atoms of each type in a molecule is called empirical formulae.
(i) Equivalent weight of element \[=\frac{Atomic\,\,weight\,\,of\,\,element}{Valency\,\,of\,\,element}\]
(ii) Eq. wt of an acid/base\[=\frac{Molecular\,\,mass}{Basicity\,\,of\,\,acid/Acidity\,\,of\,\,base}\]
(iii) Eq. wt of salts\[=\frac{Formula\,\,mass}{(Valency\,\,of\,\,cation)(No.of\,\,cations)}\]
- Expression of strength /concentration of Solution
(i) Mass percent = \[\frac{Weight\,\,of\,\,solute(gm)}{Weight\,\,of\,\,solution(gm)}\times 100\]
(ii) Normality \[=\frac{numer\,\,of\,\,gram\,\,equivalents\,\,of\,solute}{Volume\,\,of\,solution\,(lit.)}\]
(iii) Molarity =\[\frac{Number\,\,of\,\,gram\,\,moles\,\,of\,\,solute}{Volume\,\,of\,\,solution(lit.)}\]
(iv) Molality \[=\frac{Gram\,\,moes\,\,of\,\,solute}{weight\,\,of\,\,solent\,(kg)}\]
(v) Mole fraction: Mole fraction of solute \[={{X}_{A}}=\frac{{{n}_{A}}}{{{n}_{A}}+{{n}_{B}}}\]
Mole fraction of solvent \[={{X}_{B}}=\frac{{{n}_{B}}}{{{n}_{A}}+{{n}_{B}}}\]
\[{{X}_{A}}+{{X}_{B}}=1\]
- Chemical reaction: The process in which a substance undergoes change to produce new substances with new properties are known as chemical reaction. For example magnesium carbonate when heated produces magnesium oxide and carbon dioxide (i.e. new substances with new properties). A chemical change is generally accompanied by a change of state, change of colour, evolution of a gas or change of temperature etc.
- Chemical equation: The qualitative representation of a chemical reaction in a more...
