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ACIDIMETRY AND ALKALIMETRY, , 1. ESTIMATION OF SULPHURIC ACID, Expt. No.: Date:, Aim, Estimate the amount of sulphuric acid present in 100 mL of a given solution supplied in, , bottle (A) using Standard solution of HCl of strength 0.1N provided in bottle (C) and an, approximately decinormal solution of NaOH in bottle (B)', Principle, , The titration is based on the neutralisation reaction between hydrochloric acid and sodium, hydroxide in titration — I and sulphuric acid and sodium hydroxide in titration II., , , , , , , , , , , , , , , , , , Procedure, Short Procedure, DESCRIPTION TITRATION - I TITRATION - II, Burette solution Hydrochloric acid(C) Sulphuric acid(A), Pipette solution Sodium hydroxide (B) Sodium hydroxide(B), Indicator * Phenolphthalein * Phenolphthalein, End point Disappearance of pale pink | Disappearance of pale pink, colour colour, Equivalent mass of sulphuric acid = 49, , , , , , , , , , + - For convenience solutions A and C may be common for all students, and the link solution can be with varying concentration .may be given, , for practice, , *-Methyl orange can also be used, , Titration —I, Standardisation of sodium hydroxide solution, , The burette is washed with water, rinsed with distilled water and then with the given, hydrochloric acid solution. It is filled with same acid up to zero mark. The initial reading of the, burette is noted. A 20 mL pipette is washed with water, rinsed with distilled water and then with the, given sodium hydroxide solution. 20 mL of sodium hydroxide solution is pipetted out into a clean, conical flask. Two drops of phenolphthalein indicator is added into the flask. The solution turns to, pale pink in colour. The solution is titrated against standard hydrochloric acid taken in the burette., The end point of the titration is the disappearance of pale pink colour to give colourless solution., The titration is repeated to get the concordant titre value. From the titre value, the normality of, sodium hydroxide solution is calculated., , 126
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TITRATION -I, , Hydrochloric acid Vs Sodium hydroxide, , , , , , , , , , , , , , , , , , , , , , , , Volume of Sodium Burette Volume of, Si. | hydroxide solution Reading Hydrochloric acid, No (V2 mL) Initial | Final solution (Vi) Indicator, (mL) | (mL) (V1 mL), 20 0 Phenolpht, 20 0 halein, 20 0, Concordant titre value = mL, Calculation:, , Volume of Hydrochloric acid solution (V1) =, , Normality of Hydrochloric acid solution (Ni) = =, Volume of Sodium hydroxide solution (V2) =, , Normality of Sodium hydroxide (N2), , By the principle of Volumetric Analysis,, , Therefore, N2 = --, , , The normality of Sodium hydroxide solution (N2) =, , Titration II, , Estimation of sulphuric acid, , The burette is washed with water, rinsed with distilled water and then with the given sulphuric acid, solution. It is filled with same acid up to zero mark. The initial reading of the burette is noted. Since, the pipette solution is the same, no need to wash the pipette again. 20 mL of sodium hydroxide, solution is pipetted out into a clean conical flask. Two drops of phenolphthalein indicator is added, into the flask. The solution turns to pale pink in colour. The solution is titrated against sulphuric, acid taken in the burette. The end point of the titration is the disappearance of pale pink colour to, give colourless solution. The titration is repeated to get the concordant titre value. From the titre, value, the normality of sulphuric acid solution is calculated. From the normality the amount of, , mL, O.1N, 20 mL, , ViNi= V2N2, , sulphuric acid present in 100 mL of the solution is estimated., , 127
