Sodium Carbonate

 Determination of strength of 0.1(N) H₂SO₄ Solution by standard 0.1(N) Sodium carbonate (Na₂CO₃) solution.

PRINCIPLE :

                This can be considered as the neutralization reaction between a strong base (e,g. 0.1(N) Na₂CO₃)  and strong acid (e.g. 0.1(N) HCl, 0.1(N) H₂SO₄ etc.) of course CH₃COOH is a weak and organic acid. The following reaction takes place between them.

                                                       

                                          H⁺     +     OH ^-      ––––––>       H₂O

To determine the strength of the acid the following equation is used :-

                               

                           V₁S₁ = V₂S₂     where, S₁ = Strength of acid solution

                                                           V₁ = Volume of acid solution

                                                           S₂ = Strength of base solution

                                                           V₂ = Volume of base solution

CHEMICALS :

              a)  0.1 (N)  H₂SO₄   (Secondary standard solution)

            b) 0.1 (N)  Na₂CO₃     (Primary standard solution)

            c)  Indicator  -  methyl orange ( for H₂SO₄ , HCl  )

                                  -  Phenolphthalein  (for CH₃COOH)

            

APPARATUS :

a)     Conical flask

b)    Pipette

c)     Burette

d)    Funnel

e)     Volumetric flask

f)      Beaker

g)     Measuring cylinder

                                                                                                               

PROCEDURE :

                   i) Filling the burette : A clear and dried burette is filled  with 0.1 (N) acid solution and mark is adjusted with respect to zero .

                   ii) Placement of 0.1(N) acid solution in conical flask by pipette :-  A clear and dried conical flask is used to take 0.1(N) Na₂CO₃ solution from the volumetric flask to the conical flask .Take  10ml of  0.1(N) Na₂CO₃ solution in aconical flask, add 10ml of distilld water and 2-3 drops of  methyl orange. The color becomes yellow. Add 10ml distilld water and 3-4 drops Phenolphthalein for CH₃COOH . This color becomes red .

                  iii) wipe out the bottom of the conical flask and place a peace of white paper below it. Take initial burette reading. Now acid drops of acid solution from the burette to the conical flask along with gently shaking. A drop of acid solution will make it orange color but this color will fade  away rapidly.when the end point reaches, then the color becomes orange. Taken the final burette reading and fill the table for each acid .

                                                  Table for 0.1(N) H₂SO₄  :-

Solution             No.	Volume of  base	Initial burette reading	F.B.R	Difference	Mean
1	10
1	10
1	10

         Where,  

                      V₁ = Volume of acid              =                              ml

                      S₁ = Strength of acid ( ? )      =                               (N)

                      V₂ = Volume of base              =                              ml

                      S₂ = Strength of base              =                              (N)         

                                                                                                                

             V₁ S₁  =   V₂ S₂

         

      Or,                 V₂ S₂

            S₁   =   ----------------  =  ------------------  =                      (N)

                                V₁   

    

                Strength of acid ( H₂SO₄ )   =                    (N)

                 

                                                                                              

RESULT :-

                (a)   Strength  of  H₂SO₄    0.1(N)   =                  (N)

        

PRECAUTION :-

                  i)   Taken necessary step to prevent from the stop cork of  burette.

               ii)   Acid Solution from burette should be added slowly.

               iii)   Not more then 3-4 drops of methyl orange should be used.

               iv)   Difference of acid Solution between two titrations should not vary  more than 0.2ml . If it is high , repeat the titration.

               v)    In case of titrations of CH₃COOH used Phenolphthalein Indicator.