Chemistry Practicals For Class IX (Science Group) - Experiment No. 6: To standardize the given solution of sodium Hydroxide using Oxalic acid solution.

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EXPERIMENT NO. 6

TO STANDARDIZE THE GIVEN SOLUTION OF SODIUM HYDROXIDE USING OXALIC ACID

APPARATUS:

• Burette
• Beaker
• Indicator bottle
• Pipette
• Burette stand
• Conical flask
• Funnel

CHEMICALS:

• Sodium hydroxide solution
• Phenolphthalein Indicator
• Oxalic acid solution of known molarity (0.1M)

THEORY:
Titration is the method of quantitative analysis used for determining the concentration of a solution of unknown concentration using a standard solution.

EQUATION:

METHOD:

• Wash all the apparatuses thoroughly with water. Rinse burette with a little quantity of sodium hydroxide solution.
• Rinse the pipette with oxalic acid solution.
• Clamp the burette in an iron stand vertically.
• With the help of funnel, fill the burette with sodium hydroxide solution.
• Remove the air bubbles by drawing some solution from the burette.
• Fill the burette again and assuring that the lower meniscus coincide the zero mark.
• Pipette out 10 ml of oxalic acid solution in a conical flask.
• Start the addition of alkali (NaOH) solution from the burette into the conical flask drop by drop with constant shaking until very faint pink colour persists. This is the end point.
• Record the final reading of the lower meniscus in the burette.

FIND OUT THE DIFFERENCE BETWEEN INITIAL AND FINAL READING

• Find volume of NaOH by subtracting initial reading from final reading to neutralize.
• 10 ml of oxalic acid.
• Throw the contents of conical flask and wash with water.
• Take final reading of first step as initial reading of next step.
• Repeat the procedure of titration in the same manner till three similar readings (Concordant obtained)

OBSERVATIONS:
Solution in the burette (NaOH)
Molarity of NaOH solution M₁ = ?
Volume of NaOH solution (Concordant volume) V₁ = ?
Number of Moles od NaOH (from equation) n₁ = ?

SoIution in the conical flask (Oxalic acid)
Molarity of Oxalic acid M₂ = 0.1 M
Volume of oxalic acid used for each burette reading V₂ = 10 ml
No. of Moles of oxalic acid (from balanced equation) n₂ = 1
Indicator used = Phenophthalein
Colour change • Colourless to light pink
Amount of NaOH in grams /litre = ?

BURETTE READING

S.No.	INITIAL BURETTE READING (mI)	FINAL BURETTE READING (mI)	VOLUME OF NaOH SOLUTION USED (mI)	CONCORDANT VOLUME (mI)

CALCULATION OF MOLARITY:

CALCULATION OF AMOUNT OF NaOH / Liter
Molar mass of NaOH = 40 g

FORMULA:
Amount of NaOH / Liter = Molarity of NaOH x Molar mass of NaOH
= M₁ = 40
= ________

RESULT:
The molarity of given NaOH solution M₁ = _______ M
Amount of NaOH / Liter = __________ g

PRECAUTIONS:

• Note the lower meniscus of alkali solution in the burette.
• Remove air bubble from the jet of the burette.
• Rinse the burette and The pipette with NaOH and oxalic acid respectively.
• All the should be thoroughly washed.
• Only 1 or 2 drops of indicator should be used.
• The pipette should not be down to dropout the solution.
• The lower meniscus of the solution should be read.
• The pipette should not be blown to dropout the solution.
• The flask should be shaken after each addition of the solution.

Special Thanks to Sir Sajjad Akber Chandio