탄자니아에서의 화학 수업교안(Volumetric analysis)

chapter 5. 

5.1 Volumetric analysis

volumetric analysis is a branch of practical chemistry that deals with determination of accurate volumes and concentration of reacting solutions. The concentration of a given solution can be determined using a standard solution in titration.

5.2 Apparatus for volumetric analysis

For volumetric analysis you may need a pipette, burett, stand, white tile(white paper), conical flask, filter funnel, wash bottle, watch glass, beakers, measuring cylinder, a volumetric flask and an accurate balance.

  

5.3 Standard solution

A standard solution is a solution of known concentration.

The concentration of a standard solution is expressed in per litre(mol/dm3). It is usually indicated by letter M for molarity.

In volumetric analysis, one of the solutions must have a known concentration. 

Experiment 1. To prepare a standard solution of sodium carbonate

Materals required

Accurate balance, watch glass, spatula, glass rod, beaker(250cm3), filter funnel, wash bottle. Dry anhydrous sodium carbonate.

<Procedure>

1. Weigh a clean watch glass accurately.

2. Weigh between 2.5g and 3.0g of pure anhydrous sodium carbonate and put it on to the watch glass.

3.Weigh the watch glass plus carbonate accurately. Subtract the mass of the watch glass to find the mass of the carbonate(weighing by difference). 

4. Tap the sodium carbonate slowly into a 250 cm3 beaker containing 100 cm3 of distilled water. Stir the mixture with a glass rod.

5. Rinse the last particles of sodium carbonate from the watch glass into the beaker using pure water from a wash bottle. <fig 5.4>

6. Without losing even a fraction of a drop, transfer all the solution into a 250 cm3 volumetric flask. You may use a glass rod and filter funnel.

7. Rinse the beaker and filter funnel at least twice with pure water, and transfer the liquid into the flask.

Add distilled water to the flask until the meniscus just rests on the graduation mark. <fig5.5>

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