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Preparation of standard solutions of oxalic acid

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Practical 05
2021
Dr. Tariq Masood, Assistant Professor, Agricultural Chemistry & Biochemistry Page 1
Standardization of Sodium Hydroxide Solution (Approx. 0.1 N) by standard
solution of Oxalic Acid (0.1 N exact)
Reagents:
Preparation of standard solution of oxalic acid
Equivalent weight of Oxalic Acid, (COOH)
2
.2H
2
O = 126 /2 = 63g
To prepare of 1000 ml of 0.1 N solution of Oxalic Acid = Eq. wt x Desired Normality x desired volume
1000
= 63 x 0.1x 1000
1000
= 6.3 g
Preparation of 0.1 N (approx.) NaOH Solution
NaOH 0.1 N Approx. solution in 1000 ml = Eq. wt of NaOH X Desired Normality X Desired Volume
1000
= 40 X 0.1 X 1000
1000
Approx. 0.1 N NaOH solution in 1000 ml D. water = 4 g of NaOH
Indicator: Phenolphthalein (1% in Absolute Alcohol)
Principle
It is an acid base titration. Oxalic acid will neutralize NaOH.
Apparatus
i. Volumetric Flask (250 ml)
ii. Burette
iii. Pipette
iv. Conical Flask (250 ml
End Point: Light pink color
Equation:
2 NaOH + H
2
C
2
O
4
Na
2
C
2
O
4
+ 2H
2
O
Procedure:
Take NaOH solution (Approx. 0.1N) in the burette fixed vertically on the stand. Record the
initial reading on the burette. Take 10 ml of oxalic acid (Exact 0.1N) primary standard in a
conical flask. Add Two drops of indicator and titrate carefully till the end point as indicated by

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Practical 05
2021
Dr. Tariq Masood, Assistant Professor, Agricultural Chemistry & Biochemistry Page 2
the appearance of persistent light pink color in the solution. Take three consecutive titration
readings.
Calculation (Example)
No
Initial Reading
Final Reading
Difference
1
0
8.5 ml
8.5 ml
2
8.5 ml
16.5 ml
8.0 ml
3
16.5 ml
25.5 ml
9.0 ml
Mean
8.5 ml
The Exact Normality of NaOH (Approx 0.1 N) will be calculated by a formula as:
NaOH Oxalic Acid
N
1
V
1
= N
2
V
2
N
1
= N
2
XV
2
V
1
Where N
1
= Normality of NaOH found
V
1
= Volume of NaOH (Burette reading) say 8.5 ml
N
2
= Normality of Oxalic acid
V
2
= Volume of Oxalic acid
Normality of NaOH found = Normality of Oxalic Acid X Volume of Oxalic Acid
Volume of NaOH (Burette reading)
Normality of NaOH found = 0.1 X 10 = 0.12 N
8.5
The volume required to prepare exact 0.1 N solution of NaOH in 100 ml
= NaOH observed values = NaOH required values
N
1
V
1
= N
2
V
2
V
1
= N
2
V
2
N
1

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Practical 05 2021 Standardization of Sodium Hydroxide Solution (Approx. 0.1 N) by standard solution of Oxalic Acid (0.1 N exact) Reagents: Preparation of standard solution of oxalic acid Equivalent weight of Oxalic Acid, (COOH) 2 .2H2O = 126 /2 = 63g To prepare of 1000 ml of 0.1 N solution of Oxalic Acid = Eq. wt x Desired Normality x desired volume 1000 = 63 x 0.1x 1000 1000 = 6.3 g Preparation of 0.1 N (approx.) NaOH Solution NaOH 0.1 N Approx. solution in 1000 ml = Eq. wt of NaOH X Desired Normality X Desired Volume 1000 = 40 X 0.1 X 1000 1000 Approx. 0.1 N NaOH solution in 1000 ml D. water = 4 g of NaOH Indicator: Phenolphthalein (1% in Absolute Alcohol) Principle It is an acid base titration. Oxalic acid will neutralize NaOH. Apparatus i. Volumetric Flask (250 ml) ii. Burette iii. Pipette iv. Conical Flask (250 ml End Point: Light pink color Equation: 2 NaOH + H2C2O4 Na2C2O4 + 2H2 ...
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Awesome! Perfect study aid.

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