Experiment-6


FE 211 09.11.2004

EXPERIMENT 6

LAB REPORT

Submitted By : Mutlu DEMİREL Group: 3

MATERIALS:

Ca containing sample , beaker , pipette , buret , bunsen burner , florence flask , HCI , , Methyl Orange , funnel , thermometer , ,

PURPOSE:

Determination of Calcium in a sample.

METHOD:

Volumetric method.

THEORY:

Calcium dissolves out of almost all rocks and is, consequently, detected in many waters. Waters associated with granite or siliceous sand will usually contain less than 10 mg of calcium per litre. Many waters from limestone areas may contain 30-100 mg l-1 and those associated with gypsiferous shale may contain several hundred milligrams per litre. Calcium contributes to the total hardness of water. On heating, calcium salts precipitate to cause boiler scale. Some calcium carbonate is desirable for domestic waters because it provides a coating in the pipes which protects them against corrosion.

PROCEDURE:

5 mL Ca containing sample and 10 mL of HCI were poured in a beaker and diluted to 150 mL . Then the solution was heated to remove . After that 50 mL warm and 3-4 drops methyl orange were put into solution. We waited for hours to observe the precipitate. Then the solution was filtered and washed to remove the precipitate. The precipitate was put into flask with filter paper. 150 mL distilled water and 50 mL 6M were added to flask. Soon the solution was heated to 60 to dissolve ppt. Finally the hot solution was titrated with 0.02M

RESULTS AND CALCULATION :

Volume = 21.3 mL

Molarity of =10 g/L

Volume of sample = 5 mL

Density of sample = 10 g/L

Number of mole = mol

Number mole of

=

Weight =

weight of sample =

Percentage of =

DISCUSSION:

In this experiment calcium is determined by an indirect volumetric method . The method is based on precipitating ions with oxalate as . With this manner was added the solution and calcium oxalate is formed : There were some important factors to apply during the procedure. Addition of HCI must be done slowly to avoid loss by splattering due to the evalution. Our aim was to drive off the while we heat the solution. Because is acidic and may effect our result. While filtrering the solution Watmann 42 paper was used . This filter paper ha narrow pores. So the loss of precipitate was prevented. Then the precipitate was put into a beaker with filter paper , and 6M was added to it. This was done to coprecipitate the again. Finally our solution was titrated with 0.02M until the pink color was observed. The used was used for our calculation. During the procedure HCI was not used to solve our Ca containing sample. Also all titration procedures have an error becaus of the differance between the volume of equivalence point and the end point.

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