Sodium hydroxide against oxalic acid titration

(Write on both sides the ruled and unruled Sheet)

Aim:

Prepare M/20 oxalic acid solution, and using this solution determine the strength of the given sodium hydroxide (NaOH) solution

(Write on unruled Sheet) 

Chemical Equation: 

in Sodium hydroxide against oxalic acid titration, the equation is as below

Indicator: Phenophthelene 

End Point / Colour Change: Colourless to Light Pink

In Sodium hydroxide against oxalic acid titration, the endpoint is light pink color

Observation Table:

Calculation:

a₁M₁V₁ = a₂M₂V₂

a₁ = Basicity of acid (Oxalic acid Dibasic acid)

M₁ = Molarity of Oxalic Acid (M/20)

V₁ = Volume of oxalic acid (Pipette volume)

a₂ = Acidity of base (NaOH Monoacidic base)

M₂ = Molarity of NaOH (To find out)

V₂ = Volume of NaOH [Concordant volume (11.0 mL)]

M₂ = (a₁M₁V₁)/ a₂V₂

Substitution values molarity of NaOH is 

M₂ = 0.0909 M

Calculation for Strength of NaOH:

Strength (in g/L) = Molarity x molecular weight of NaOH

                                =  0.0909 x 40 =3.63 gm /L 

(Write on ruled Sheet) 

Procedure:

1.  Preparation of 0.05 M Standard Solution of Oxalic Acid
2. Sodium Hydroxide against Oxalic Acid titration.

1. Clean the burette thoroughly, wash it with distilled water and finally rinse it with sodium hydroxide solution. (Always rinse the burette with the NaOH solution).
   Clamp the burette vertically in a burette stand.
2. Fill sodium hydroxide solution into the burette through a funnel above the zero mark.
3. Remove the air gap, if any, from the nozzle of the burette by running the solution forcefully from the burette nozzle.
4. Remove the funnel before noting the initial reading of the burette. Also while noting the reading, see that no drop of the liquid is hanging at the nozzle of the burette.
5. Note the initial reading by keeping the eye exactly at the same level as the meniscus of the solution.
6. Pipette out 10 mL of oxalic acid solution in a washed and dried conical flask. Always wash the pipette with water and rinse with the oxalic acid (solution to be measured) before pipetting out the liquid.
7. Add 1-2 drops of phenolphthalein indicator to the conical flask. Place the flask over the glazed tile. Titrate the acid with sodium hydroxide solution
   till a very faint permanent pink color is obtained. Add sodium hydroxide solution in small amounts initially and then dropwise

Result: 

The strength of the given NaOH solution is 3.63 gm /L 

Precautions:

1. Always rinse the burette with the solution, which is to be taken in it.
2. Remove the air gap from the burette before titrating the solution. Make sure that the nozzle of the burette is also filled.
3. Never forget to remove the funnel from the burette before noting the readings of the burette and ensure that no drop is hanging from the nozzle.
4. Always read the lower meniscus for all transparent solutions and the upper meniscus for colored solutions.
5. To note the burette readings place the eye exactly at the level of the meniscus.
6. Never hold the pipette at the bulb.
7. Never use the pipette and burette with a broken nozzle.
8. Never suck a strong acid or an alkali with the pipette.
9. Always keep the lower end of the pipette dipped in the liquid while sucking the liquid.
10. Do not blow out the last drop of the solution from the jet end of the pipette into the flask.
11. The concentration (strength) of the solution must be calculated up to the fourth place of the decimal.

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