Mole concept:Just as in our daily life, we use the term dozen to denote the number 12 while dealing with things such as pencils and note-books etc. Similarly,in chemistry,we use the term mole to denote 6.022*1023 particles such as atom,molecules or ions etc.This number 6.022*1023,is called avagardo's number.
avagadro's number may be defined as the number of atoms present in one gram of the element or the number of molecules present in one gram molecule of the substance.
Definition of mole: A mole may be defined as the amount of any substance which contains avogadro's number (6.022*1023) of particles (atoms,molecules,ions or electrons etc. of that substance and has mass equal to one gram atomic mass or one gram molecular mass etc. as the case may be.
Solutions:A solution is a homogeneous mixture of two or more pure substances whose composition can be varied within certain limits.
solute+solvent-solution
the substance which is dissolved and is present in lesser quantity is called solute and the substance in which solute is dissolved and is present in greater quantity is called solvent.
Ways of expressing concentration of a solution.
The concentration of a solution can be expressed in a number of ways:
(1).Strength:The amount of solute in grams present in one litre of the solution.
(2).Molarity (M):The number of moles of solute dissolved per litre of the solution.
(3).Molality (m):The number of moles of solute dissolved in 1000g(or kg )of the solvent.
(4).Normality(N):The number of gram equivalents of the solute dissolved per litre of the solution.
(5).Mole Fraction:The ratio of the number of moles of one component to the total number of moles of all the components present in the solution.
(6).Mass Fraction: The ratio of the mass of one component to the total mass of all the components present in the solution.