Volumetric Analysis Class 11

Experiment:- 2

1. AIM :- To prepare M/ 20  solution sodium carbonate solution.

2. REQUIREMENTS :-

2 (A) Apparatus Required

Watch glass, chemical balance, weight box, 250 mL beaker, glass rod, 250 mL measuring flask and wash bottle.

2(B) Chemicals Required

Anhydrous sodium carbonate (solid) and distilled water.

3 PRINCIPLE / THEORY :- It is based on the principle which involves quantitative estimation of the amount of any substance present in a solution through volume measurements.

Sodium carbonate is a primary standard. Its molecular mass is 106. To prepare M / 20 Na2C03 solution, 10.6 g of Na2C03 should be dissolved per litre of the solution. 

So to prepare 250 mL of M / 20 Na2C03 solution.

M = w / GMM × V (in Litre)

M = Molarity of solution 

W = Weight of solute ( Sodium carbonate )

GMM = Gram Molecular Mass of solute (Sodium carbonate  )

5.CALCULATION :

To prepare M/20 Sodium carbonate  solution,10.6  g of Sodium carbonate  is to be dissolved in distilled water to prepare 1 litre of solution. 

Therefore, to prepare 250 ml (in 250 ml volumetric flask) of M/20, the required weight of Sodium carbonate (Na2CO3)  is – 

M = w /  GMM × V (in Litre)

M = w x 1000 /  GMM  x V (in ml)

and 

w = M x GMM x V (in ml) / 1000

w = 1/20 mol/L x 106 g  / mol  x 250 ml  / 1000

w = 1.325  g

To Sodium carbonate prepare M/20 sodium carbonate (Na2C03) solution in 250 ml volumetric flask 1.325  g of sodium carbonate is required.

6.PROCEDURE

A.Take a watch glass. Clean it properly with distilled water and then dry it.

B. Weigh the clean dry watch glass using a chemical balance and record its weight in the practical notebook.

C.  Weigh 1.325 g of sodium carbonate on the watch glass and record this weight in the notebook.

D. Transfer oxalic acid to a clean in 250 ml.of volumetric flask  carefully with the help of funnel and wash bottle. Wash the watch glass with distilled water to ensure all the crystals sticking to the watch glass are transferred into a volumetric flask. Finally wash the funnel thoroughly with distilled water so that sodium carbonate solution is sticking to the funnel.

Dissolve sodium carbonate by Stopper the flask and shake volumetric flask.The total volume of  solution for this purpose should not be more than 250 ml therefore fill the distilled water in 250 ml volumetric flask up to the mark of ring.

The final addition of water must be drop wise. The lower level of the meniscus touches the mark on the measuring flask. Label it as M/20 sodium carbonate solution.

7.PRECAUTIONS

1.Weighing of the sodium carbonate crystals should be accurate.

2.washing of the watch glass and beaker should be done thoroughly with distilled water.

3. The lower meniscus should be on the mark because oxalic acid solution is colourless

4. Last few drops of distilled water should be added using a pipette or dropper or wash bottle.

Volumetric Analysis (Titration)

EXPERIMENT NO. 3 

1.AIM  / Objective :-

                            To determine the strength of the given sodium hydroxide solution. You are provided with M / 20 oxalic acid solution. 

PRINCIPLE:-  It is based on the principle of volumetric analysis in which volume of the given solution is required to react quantitatively with the solution of another substance of known concentration. The process involved in volumetric analysis is called titration.

2.THEORY :- Oxalic acid solution is titrated against sodium hydroxide solution using phenolphthalein as indicator.

3.CHEMICAL EQUATION :-

    COOH   

    I

    COOH . 2 H2O + 2Na0H –>       

    COONa

    I

    COONa + 4H20

Oxalic acid is a dibasic acid and sodium hydroxide is a monoacidic base.

4.INDICATOR :- Phenolphthalein.

5.END POINT :-  Colourless to pink (Alkali in burette).

6.REQUIREMENTS

6 a-Apparatus Required:- Burettee, Pipettee, conical flask, funnel, dropper and buretteestand.

Chemicals Required :- Oxalic acid,     hydroxide and phenolphthalein.

7. PROCEDURE

A.Wash burette with water and then rinse it with the given sodium hydroxide solution. Clamp it vertically in the burette stand.

B. Fill the burette with sodium hydroxide solution and note the reading of the lower h; meniscus of NaOH solution. There should be no air bubble in the stopcock.

C.Rinse the pipette with the given oxalic acid solution.

D.Pipette out 20 mL of the given oxalic acid solution in a conical flask.

E.  Add J to 2 drops of phenolphthalein indicator with dropper and place just below the nozzle of the burette over a white glazed tile.

F. Note down the lower meniscus of the solution on the burette and record it as the initial burette reading.

G. Start adding NaOH solution drop wise from the burette. Swirl the solution in the conical flask until colour of the solution changes to permanent pink colour. Read the lower meniscus of the solution in the burette and record it as final reading.

H.Repeat the procedure till three concordant readings are obtained.

8.OBSERVATIONS

Molarity of the given oxalic acid solution = M/20

Volume of oxalic acid solution taken for each titration = 20 mL (V1).

Solution in the burette = NaOH.

Solution in the conical flask = Oxalic acid solution.

Observation Table :-

S.No.	Volume of oxalic acid (in pipettee) in ml		Burettee Reafing		Volume of NaOH used in ml	Concordant Reading in ml
			Initial	Final	Final -Initial
1
2
3

Concordant volume = x mL.

9.CALCULATIONS

According to the equation, 1 mole Of oxalic acid reacts with 2 moles of sodium hydroxide.

Voxalic acid  x  No. of moles of oxalic acid in the balanced equation NaOH    No. of moles of NaOH in the balanced equation

Molarity of the given oxalic acid solution =  M / 20

20 x 1 / 20 /

—————-=    1/2

x x M (NaOH)

M(NaOH)= 2/× mol /L    

Strength of NaOH = Molarity x Molar mass

= 2/x x 40 = 80/x g/ml

10.RESULT :- The strength of the given sodium hydroxide solution is x/80 gL

11.PRECAUTIONS

A.Rinse the burette with the solution to be taken in the burette.

B. Rinse the pipette with the solution to be taken in the conical flask.

C.Wash the conical flask with distilled water after every titration.It is not needed of you do not pour more from burettee after end point.

D Do not rinse the conical flask.