Preparation and Standardization of 0.1 M Sodium Hydroxide
How to prepare 0.1 m sodium hydroxide ?
Preparation of 0.1 M Sodium Hydroxide (NaOH) or 0.1 N Sodium Hydroxide (NaOH):
Take a 100 mL of purified water or water in 1000 mL volumetric flask. Add 4.0 g of Sodium Hydroxide (NaOH) carefully using calibrated Balance.
Add approx. 700 mL water. Allow Solution to *cool down to Room Temperature.
Make up the volume upto 1000 mL with purified water.
* Because of Thermodynamic reaction volume may vary, so final volume shall be added after partial addition of volume.
Calculation:
Molecular weight of Sodium Hydroxide (NaOH)= 40g
Equivalent Weight of Sodium Hydroxide (NaOH)= 40/1= 40g
40 gm of Sodium Hydroxide (NaOH) in 1000mL Water= 1N NaOH
20gm of Sodium Hydroxide (NaOH) in 1000mL Water= 0.5 N NaOH
4.0 gm of Sodium Hydroxide (NaOH) in 1000mL Water= 0.1 N NaOH
Standardizing a 0.1 N Sodium Hydroxide (NaOH) Solution
1. Standardizing a Sodium Hydroxide (NaOH) Solution using potassium hydrogen phthalate (KHP)
To standardize the 0.1 M NaOH solution (the titrant) with potassium hydrogen phthalate (KHP, Formula: KC8H4O4H) using phenolphthalein as the indicator.
Dry primary standard potassium hydrogen phthalate (KHP) for about two hours at 120°C in Oven.
Accurately Weigh 500 mg of previously dried potassium hydrogen phthalate (KHP) (Molecular Weight = 204.23 g/mol) into a flask.
Dissolve your sample in 75 mL of carbon dioxide free water.
Add 2-4 drops of phenolphthalein as an indicator into the flask (Erlenmeyer Flask).
Obtain approximately 100 mL of NaOH solution in a clean, dry beaker.
Prepare the burette for titration by rinsing with 2 aliquots of solution. Fill the burette and record the initial volume to 0.1 mL.
Begin titrating when pink appears for the first time. To determine the total amount most accurately, add the NaOH dropwise toward the endpoint.
Record the final burette reading. If time allows, repeat the titration.
Calculation:
Normality of NaOH = (weight of KHP ) ÷ 0.20422 * mL used of NaoH solution in titration.
2. Standardizing a Sodium Hydroxide (NaOH) Solution using Oxalic Acid (H2C2O4. 2H2O)
Titration of Sodium Hydroxide (NaOH) and Oxalic Acid Solution, Clean the burette carefully, than wash it with distilled water and finally rinse it with sodium hydroxide (NaOH) solution.
Rinse the burette well with the solution that will be used in it. In a burette stand, clamp the burette vertically.
Fill 0.1 N Sodium hydroxide (NaoH) solution into the burette using funnel above the zero mark.
By vigorously flowing the solution from the burette nozzle, remove any air traps that may have formed.
Pipette out 10 mL of oxalic acid solution in a washed and dried conical flask.
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 colour is obtained. (Take 20 mL of 0.5 N Oxalic Acid to start the titration)
Add sodium hydroxide solution in small drop wise.
In the burette, read the lower meniscus of the solution once again and record it as the final reading.
Repeat the procedure for 3 (three) concordant readings are obtained.
Calculation:
Molecular weight of Oxalic Acid = 126 g,
Equivalent weight of Oxalic Acid =63 g (as, 126/2)
63 g of Oxalic Acid in 1000 mL of Purified Water= 1 N Oxalic Acid
31.5 g of Oxalic Acid in 1000 mL of Purified Water= 0.5 N Oxalic Acid
Molarity of NaOH solution can be calculated by using the equation:
Oxalic acid Sodium hydroxide
a1 M1V1 = a2 M2V2
Where,
M1 and V1 = molarity and volume of the oxalic acid solution.
M2 and V2 = molarity and volume of the sodium hydroxide solution.
a1 and a2 = the basicity of oxalic acid and acidity of sodium hydroxide.
Here,
a1= 2 and a2 = 1.
Also,
Molar mass:
Oxalic acid, [(COOH) 2.2H2O] = 126 g mol–1
Sodium hydroxide (NaOH) = 40 g mol –1
Calculate the con. of sodium hydroxide (NaOH) solution in g/L by using the equation given below.
Concentration (strength) in g/L = Molarity (M) × Molar mass
3. Standardization of a 0.1 N sodium hydroxide (NaOH) solution using Benzoic Acid
Equation:
HC7H5O2(aq) + NaOH(aq) = NaC7H5O2(aq) + H2O(l)
Dissolve around 200 mg of benzoic acid in 100 mL of carbon dioxide-free water, warm until completely dissolved, and cool down to RT (Room Temperature).