Preparation of Standard Solution of Sodium Carbonate

A standard solution is a solution whose concentration has been accurately determined. Standard solutions are prepared from highly pure chemicals and the exact concentration is determined by a process called standardisation. The substance available for the standardisation of a solution that is highly pure and is called a primary standard.

Aim

To prepare the 250 cm³ of N/10 standard solution of sodium carbonate.

Theory

Sodium carbonate is essentially insoluble in nearly saturated sodium hydroxide. The insoluble sodium carbonate will settle to the bottom of the container after the saturated NaOH has equilibrated for a couple of days. The supernatant can be withdrawn carefully to prepare a diluted NaOH solution free of sodium carbonate. The water for preparing NaOH standard solution should be boiled to remove any dissolved CO₂, because dissolved CO₂ can cause a titration error. To prepare the standard solution of sodium carbonate, The equivalent weight of sodium carbonate =

Materials Required

1. Chemical balance
2. Watch glass
3. Weight box
4. 250ml beaker
5. Glass rod
6. 250ml measuring flask
7. Wash bottle
8. Weighing tube
9. Sodium Carbonate
10. Funnel
11. Funnel stand
12. Distilled water

Apparatus Setup

Procedure

1. Take a watch glass, wash it with distilled water and dry it.
2. Weigh the exact amount of clean and dried watch glass and record its weight in the notebook.
3. Weigh correctly on the watch glass with 1.325 g of sodium carbonate and record this weight in the notebook.
4. Using a funnel, transfer sodium carbonate softly and carefully from the watch glass into a clean and dry measuring flask.
5. Wash the watch glass with distilled water to move the particles that stick to it into the foam with the assistance of a wash bottle.
6. For this purpose, the volume of distilled water should not exceed 50 ml.
7. Wash funnels several times with distilled water to move the sticking particles into the measuring flask using a wash bottle. Add water in tiny quantities while washing the funnel. The distilled water quantity used for this purpose should not exceed 50 mL.
8. Using a wash bottle, wash the funnel carefully with distilled water to pass the solution attached to the funnel into the measuring flask
9. Turn the flask of measurement until the sodium carbonate dissolves.
10. Using a wash bottle, thoroughly add enough distilled water to the measuring flask just below the etched mark on it.
11. Add the last few mL of distilled water drop into the measuring flask until the reduced meniscus level just touches the mark.
12. Put the stopper on the mouth of the flask and shake softly to make the entire solution uniform. Calculate it as a solution of sodium carbonate N/10.

Observations

Results and Discussion

250cm³ of decimolar or N/10 standard solution of sodium carbonate is prepared.

Precautions

1. While weighing do not spill the substance on the balance pan
2. While preparing the laboratory reagent apron should be used.
3. Bases are highly corrosive so they should be handled with extreme care.
4. Watch glass must be dry.
5. Funnel should be washed thoroughly several times.
6. Shaking of solution should be done thoroughly so that it may become uniform.
7. While making the solution the solvent should be added such that the lower meniscus of the solvent must be on the mark of the measuring flask.
8. Last few drops should be added using a pipette to avoid extra addition of distilled water above the mark on the neck of the measuring cylinder.

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