Preparation and standardization of various molar and normal solutions.

1. Preparation and standardization of
various molar and normal solutions-
Oxalic acid
Sodium hydroxide
Hydrochloric acid
Sulphuric acid
Potassium permanganate
Nidhi Sharma

2. Preparation and Standardization of Oxalic acid-
Oxalic acid is available in pure state and its standard solutions can be prepared by the direct
method. Molecular formula of oxalic acid is C2H2O4.2H2O.
Preparation of oxalic acid solution-
• Molecular weight of oxalic acid is 126gm.
• Equivalent weight of oxalic acid is 126/2= 63gm
• 63gm of oxalic acid dissolved in 1000ml water = 1N Oxalic acid
• 31.5gm of oxalic acid dissolved in 1000ml water = 0.5N Oxalic acid.
Standardization N/10 oxalic acid solution (Primary standard)-
• Place the oxalic acid solution in a flask and add few drops of phenolphthalein indicator.
• Pour 0.1N solution of NaOH in the burette but since it is still not standardized, the
concentration will be considered as unknown.
• Add NaOH solution dropwise to the analyte until the end point is reached.

3. Apply the equation-
N x V (oxalic acid) = N' x V' (NaOH).
where N,V, and V' are known.
Find out N' which will not be far from 0.1 (probably 0.13 to 0.97).

4. Preparation and Standardization of sodium hydroxide-
Sodium hydroxide is deliquescent (absorbs moisture from the atmosphere) solid.
It cannot be weighed accurately.
Molecular weight of NaOH = 40gm
Equivalent weight of NaOH = 40/1 =40gm
Preparation-
40 gm of NaOH dissolved in 1000 ml water = 1N NaOH
20gm of NaOH dissolved in 1000ml water = 0.5N NaOH
4 gm of NaOH dissolved in 1000ml water = 0.1N NaOH

5. STANDARDIZATION OF THE NaOH SOLUTION-
Weigh accurately 0.63 gm of oxalic acid into a 100 ml volumetric flask and make
up to 100 ml volume with distilled water. Pipette out 20 ml solution and titrated
0.1 NaOH using phenolphthalein as indicator. Continue the titration to get the
concordant value.
N1V1 =N2V2
N2 = N1V1/ V2
N1 = 0.1 N = Normality of Oxalic acid Solution,
N2 = ? = Normality of NaOH
V1 = 20 ml = Volume of Oxalic acid Solution,
V2 = 19.8 ml = Volume of NaOH
N2 = N1 V1/ V2

6. Preparation and Standardization of Hydrochloric acid-
Preparation of Hydrochloric acid-
• Take about 100 ml of water in a cleaned & dried 1000ml volumetric flask.
• Add about 8.5ml of Conc. Hydrochloric acid with continuous stirring.
• Add more about 700 ml of water, mix and allow to room temperature.
• Make up the volume 100ml with water. Mix solution thoroughly.
• Keep the solution for at least one hour and then carry out the standardization.
Standardization of Concentrated acids (HCl)-
• Weigh accurately about 1.5gm of anhydrous sodium carbonate, previously heated at about 2700oC for 1
hour.
• Dissolve it in 100ml of water and add 0.1ml of methyl red solution.
• Add the acid slowly from a burette, with constant stirring, until the solution becomes faintly pink.
• Heat the solution to boiling, cool & continue the titration.
• Heat again to boiling & titrate further as necessary until the faint pink colour is no longer affected by
continued boiling.
• 1ml of 1M hydrochloric acid is equivalent to 0.05299gm of Na2CO3

7. Calculate the molarity of solution by the following formula-
M = Na2CO3 in mg X 52.99
HCl in ml

8. Preparation and Standardization of Sulphuric acid-
Preparation of sulphuric acid (H2SO4)-
• 6ml of sulphuric acid is added to about 800ml of purified water.
• Makeup to 1000ml with purified water.
• Allow it to cool.
Standardization of Sulphuric Acid H2SO4-
• Weigh accurately about 0.2gm of anhydrous sodium carbonate, previously heated at about 2700C for 1
hour.
• Dissolve it in 100 ml of water and add 0.1 ml of methyl red solution (Indicator).
• Add the acid slowly from a burette, with constant stirring, until the solution becomes faintly pink.
• Heat the solution to boiling, cool & continue the titration.
• Heat again to boiling & titrate further as necessary until the faint pink colour is no longer affected by
continued boiling.
• 1ml of 0.1M sulphuric acid is equivalent to 0.0038gm of Na2CO3.
Calculate the molarity of solution by the following formula-
M = Na2CO3 in mg X 9.8
H2SO4 in ml

9. PREPARATION & STANDARDIZATION OF POTASSIUM PERMANGANATE-
Preparation of Potassium Permanganate-
Potassium Permanganate 0.1N- Dissolve 3.3 g of reagent grade potassium permanganate (KMnO4) in 1 L of
purified water and heat on a steam bath for two hrs. Cover and allow to stand for 24 hrs. Filter through a
fine porosity sintered glass crucible, discarding the first 25 ml. Store in a glass-stoppered, amber-colored
bottle. Avoid exposure to direct sunlight; cover the neck of the bottle with a small beaker as a protection
against dust. If manganese dioxide precipitates get forms on standing, refilter and re-standardize before
use.
Standardization of Potassium Permanganate-
• Take 20 ml of Oxalic acid solution.
• Add 5 ml of 1m Sulphuric acid.
• Warm the mixture to about 70oC.
• Titrate with potassium permanganate solution taken in the burette.
• End point is appearance of pink color that persist for 30sec.
N1 V1 =N2 V2
N2 = N1 V1/V2

10. THANK YOU