FE 211

ANALYTICAL CHEMISTRY

EXPERIMENT-2

ANALYSIS OF IRON IN A SOLUBLE

Uğur ASİT

PURPOSE:

In this experiment we are going to determine iron yield in an aqueous solution by using gravimetric method. But this time we will treat analyte more complexly.

THEORY:

Gravimetric method is one of the three subgroups of quantitative analytical method. It is based on measuring the weight of a known substance which is related to the analyte and, by using the relation, determining the quantity.

Gravimetric analyses divides into three subgroups; precipitation, volatilization, electro deposition. In this experiment we are going to use precipitation method.

As we all know solubility varies for all compounds. There are such compounds that nearly insoluble. Precipitation method is based on this principle that precipitating a soluble analyte as insoluble compound of it and weighing the precipitation.

We will separate iron crystalline precipitate by filtering and wash it. After drying and ignition we’ll weigh the pure iron.

MATERIALS:

Diluted ammonium hydroxide solution (Dilution 1 to 3). Filter paper pulp. Nitric acid solution. Methyl orange indicator (0.02 g/100 ml). Silver nitrate solution (5 g/100 ml). NH4NO3 solution (1g/100 ml). Crucible. Flask Distilled water.

PROCEDURE:

We took 5 ml of sample solution. This solution was diluted to 250 ml with water. It was started to heat solution. Filter paper pulp was added to the solution and stirred. Three drops of nitric acid were added. It was went on heating till boiling Three drops of methyl orange was added and solution titrated with ammonium

hydroxide. Solution cooled and rested to settle till clear supernatant was observed. Precipitation was filtered gently and washed with NH4NO3 till used washing

solution passed the turbidity test (Turbidity test was done with adding a few drops of AgNO3)

All content was taken to weighed porcelain crucible and paper was chared off and ignited at 800 oC.

Results were reported.

DATA:

Weight of crucible and solid = 12,3487 g

Weight of crucible = 12,2590 g

Weight of solid = 0,0897 g

CALCULATION:

DISCUSSION:

In this experiment we became more familiar to gravimetric analysis. But this time we followed a more complex procedure in order to adjust sample for precipitation reaction. We treated sample with nitric acid for all Fe ions to turn into +3 form.

For precipitation solution had to be alkaline medium so we tested the medium with an indicator. We added filter paper pulps because our precipitation was a little jelly like and could clog the pours of filtration paper.

As we know Fe is mostly found in nature as mineral forms and it is a good example for other B group metals that is found in the nature. That is why such analysis is very important in food sector.

To talk about our experiment a personal mistake occured during experiment that is why I expect a positive error in results. But experiment can said to successful.

Fe in sample : 5 ml 60 g Fe

1 lt1 lt

1000 ml1 mole Fe

55.847 g Fe

= 0.0053 mole Fe

Found Fe : 0.0897 g Fe2O3 1 mole Fe2O3

159.9622 g Fe2O3

2 mole Fe1 mole Fe2O3

= 0.0011 mole Fe

Percent Yield: 0.0011 mole Fe *1000.0053 mole Fe

= 20,75 %

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