Principle: In this experiment we shall determine the strength of NaOH solution by a standard solution of Oxalic Acid. This is done by means of “Titration”. Where Oxalic acid is a weak acid and primary standard substance, and Noah is a strong base and secondary standard substance . In this titration the reaction will be happen.
HOOC-COOH + 2 NaOH ——> NaOOC-COONa + 2H2O
For complete titration one mole of Oxalic acid and two mole Sodium Hydroxides are required. So the equivalent weight of Oxalic acid is equal to half of its molecular weight. If V1 is the volume of the standard Oxalic acid solution and its strength is S1 which is required for complete titration, otherhand volume of NaOH is V2 and its strength is S2
The formula required to determine the strength of NaOH solution is:-
V acid X S acid = V base X S base
or , V a X Sa = V b X S b
where ‘V’ represents volume and ‘S’ represents strength.
Apparatus: Digital balance, Measuring Flask, Wash bottle, Conical Flask, Pipette Burette, Stand and Cramps.
Chemical: Sodium hydroxide (NaOH), Oxalic Acid ( H2C2O4 ), phenolphthalein, Distilled water.
Preparation of Oxalic Acid solution:
Molecular weight of C2O4H2. 2H2O = 12 X 2 + 16 X 4 + 1 X 2 + 18 X 2
= 126
Equivalent weight = 126 / 2
= 63
1000 ml 1N solution C2O4H2 present = 63 g
100 ml 0.1N solution C2O4H2 present = 63 x 100 x 0.1 / 1000
= 0.63 g
Concentration of Oxalic acid solution = 0.63 /0.63 X 0.1 N
= 0.1 N
1. We took 0.63 g Oxalic acid and Transferred to 100ml measuring flask. It was dissolved it with distilled water. Shake the mixture so that the solute mixed completely. The solution made up to the mark.
2. We took clean burette rinsed and then filled it with Sodium Hidroxide solution. Then, the burette was stood by stand and cramps.
3. We took a pipette of 10ml which was cleaned and washed with distilled water and then rinsed with Oxalic acid solution.
4. Took 10ml solution of Oxalic acid in a conical flask from the measuring flask (Beaker if the solution pour in the beaker)with the help of an appropriate pipette.
5. Diluted with a little of water and drop 1 to 2 drops phenolphthalein indicator.
6. Then, we placed the flask upon a white paper under the burette tip.
7. Place the burette such way that its tip 1 inch up from the mouth of the conical flask. But not touch it.
8. Noted the burette reading.
9. Slowly run the NaOH solution into the Oxalic acid solution and continuously rotated the conical flask. But not touch with the tip of burette.
10. Add slowly until the solution comes colorless to light pink colors. This is the end point of the titration.
11. Noted the burette reading in the data table.
12. The difference between the initial and final burette reading gives the volume of the NaOH solution required to completely neutralize 10ml oxalic acid solution.
13. The Procedure is repeated three or four times
Table: Determination volume of NaOH
Calculation: We know, V1S1 =V2S2 Here, V1 = Volume of C2O4H2
Or, S2 = V1S1 /V2 S1 =Conc. of C2O4H2 solution
V2 =Volume of NaOH,
S2 = Conc. of NaOH =?
Result : Concentration of NaOH solution …………….. N .