MOLE CONCEPT AND GASES, MOLE CONCEPT AND SOLUTION,

 

MOLE CONCEPT AND GASES:

            One mole of any gas at room temperature and pressure always occupy 24dm3 (24000 cm³) volume.

                                                                      Volume of gas at r.t.p.

Number of moles of gas =                                                               

24dm³ (2400 cm³)

 

Whereas,

            One mole of any gas at standard temperature and pressure always occupy 22.4dm³

(22400 cm³) volume.

Volume of gas at s.t.p

Number of moles  of gas =                                                  

                                                            22.4dm³ (22400 cm³)

 

MOLE CONCEPT AND SOLUTION:

            Concentration of solution is mostly expressed in terms of molarity. It is the number is moles of solute and volume  of solution expressed in dm³.  Its unit are mole dm^-3.

 

           Number of moles of solute

Molarity =                                                     

Volume of solution in dm³

 

Mathematically;

           

            M =

            N = M x V (dm3)

            n =                            (1 dm³ = 1000 cm³)

 

If we put the value of mole in the Molarity expression.

 

      Mole

Molarity =                                         

    Volume

as;      

            mole = mass / Mr

therefore;

     Mass / Mr

Molarity =                                         

        Volume

Or

        mass

Molarity =                                         

   Volume x Mr

Or

Mass / volume = Molarity x Mr

Concentration (grams dm^-3) = Molarity x Mr

            Thus concentration of a solution has two units, one is mol.dm^-3 which is also called Molarity of the solution, and second is g.dm^-3 which is simple called concentration of the solution. In case of solution containing ions made up of single element, the formula become;

 

            Concentration (grams dm^-3) = Molarity x Ar

 

            There is another important relation which is used for calculation when concentrated solution is diluted to another concentration.

            M₁V₁ = M₂V₂

 

            Where M¹ and V¹ stands for Molarity and volume of concentrated solution and M² and V² stand for Molarity and volume of diluted solution or vice versa.