To recover blue vitriol crystals from the given mixture of copper sulphate and sodium chloride | NEB Grade XII Chemistry Practical | Nepali Educate

Experiment 01: Preparation of Decinormal Solution of Oxalic Acid

Apparatus Required

• Pipette
• Conical flask
• Beakers
• Volumetric flask
• Funnel

Chemicals Used

Oxalic acid and Distilled water

Theory

Hydrated oxalic acid is a primary standard substance and used to prepare the primary standard solution. It is a reducing agent and gets oxidized to CO₂ by losing two electrons. Its equivalent weight is \(63\).

Decinormal solution of oxalic acid contains \(1/10\)th gram equivalent of it in \(1000\)ml of solution. The weight of oxalic acid required to Prepare \(250\)ml of decinormal solution is calculated by the formula:

\[ \text{Weight required} = \left(\frac{E \times V \times X}{1000}\right) = \frac{(63 \times 250 \times 1)}{1000} \times \frac{1}{10} = 1.575\text{gm} \]

Therefore, \(1.575\) gram oxalic acid is required to prepare \(250\)ml of decinormal oxalic acid solution.

Procedure

Chemical balance was made ready for weighing. Accurately \(1.575\)gm oxalic acid was weighed and transferred into \(250\)ml of volumetric flask with the help of a funnel. The particles attached with the funnel were washed down by using water. The crystals of oxalic acid were dissolved in a minimum amount of water and then the solution was made up to the mark. Finally, the flask was covered with a lid and the solution was made homogeneous.

Observation

Weight of empty watch glass = \(W_1\)g

Weight of watch glass + oxalic acid = \((W_2 + 1.575)\)g

Weight of oxalic acid crystals = \(1.575\)g

Volume of water = \(250\)ml

Normality factor = \(\frac{\text{weight taken}}{\text{weight to be taken}} = \frac{1.575}{1.575} = 1\)

Actual normality given normality x normality factor = \(0.1 \times 1 = 0.1\)N

Result

Hence, \(250\)ml of decinormal oxalic acid solution was prepared by dissolving \(1.575\)g Oxalic acid crystals.

Conclusion

Primary standard solution can be prepared by taking the exact weight of the primary standard substance.

Precaution

1. Weight should be taken carefully.
2. At the end, water should be added drop by drop.
3. Apparatus should be handled carefully.