Etiket Arşivleri: experiment

Experiment-4

FE 211 25.10.2004

EXPERIMENT 4

LAB REPORT

Submitted By : Mutlu DEMİREL Group: 3

MATERIALS:

HCl , HAc , Phenolphthalein , Methyl Orange , NaOh , Dilute Water ,Buret ,

Erlenmayer Flask ,

PURPOSE:

In this experiment we titrated HCI and HAc mixture with NaOH to determine amounth of HCI , HAc and NaOH and the molarity of NaOH.

METHOD:

Gravimetric Analysis

THEORY:

The capacity of water to accept protons is called alkalinity. Alkalinity is important in water treatment and in the chemistry and biology of natural waters. Alkalinity serves as a pH buffer and reservoir for inorganic carbon. It helps to determine the ability of water to support algal growth and other aquatic life; thus, it can be used as a measure of water fertility. In natural waters, the species responsible for alkalinity are OH-, HCO3-, and CO32-. Alkalinity is equal to [OH-] + [HCO3-] + 2[CO32-]. The coefficient of “2” before [CO32-] is necessary because carbonate accepts two protons. However, in natural waters of pH from 7 – 9, the predominant species is bicarbonate.

Alkalinity can be measure by titration with a standard solution of HCl. The titration reaction for the bicarbonate ion is: HCO3- + H+ _ H2CO3 The endpoint can be determined with the methyl orange indicator or by measuring the pH of the solution throughout the titration. In the later case, analysis of the titration curve allows determination of the end point. Alkalinity is expressed as the number of moles of H+ required to titrate one liter of water sample or as mg CaCO3/L of water.

PROCEDURE:

5 ml HCI and 5 ml HAc was poured into a erlenmayer flask. Then 2-3 drops of methyl orange indicator was added to this solution and titrated with standart solution until the color of the solution change. Then 2-3 drops of phenolphthalein was added to the solution and again titrated with NaOH until the end point was observed.

RESULTS AND CALCULATION :

HCI = n NaOH fw of HCI = 36.5 g volume of NaOH = 8 mL

NaOH =

NaOH = n HCI = 0.0008 mol

fw of

volume of NaOH = 11 mL

NaOH = n

NaOH =

NaOH = n = 0.0011 mol

DISCUSSION:

In this titration reaction we have a mixture of strong acid , HCI , and weak acid HAc , as primary solution. The mixture of acids were titrated with base , NaOh because the Ka for weak acid was abouth or less so two end point was observed. The first end point was for HCI , the second was for HAc . To observe the end points of this two different acids, two different indicators were used. Methyl orange for HCI and Phenolphthalein for HAc.

Experiment-3

FE 211 25.10.2004

EXPERIMENT 3

LAB REPORT

Submitted By : Mutlu DEMİREL Group: 3

MATERIALS:

0.1 M NaOH , Potassium Hydrogen Phthalate , Desiccator , Phenolphthalein , 5 ml Vineger , Distilled water , Flask , Buret , Erlenmayer Flask

PURPOSE:

In this experiment our aim is to determine the molarity of NaOH and weight percentage of with neutralization titration.

METHOD:

Gravimetric Analysis

THEORY:

Both NaOH and HCl are frequently used reagents: the former an example of a strong base, and the latter an example of a strong acid. This classification comes from the position of the equilibrium when each is placed in an aqueous solution:

Experiment-2

FE 211 18.10.2004

EXPERIMENT 2

LAB REPORT

Submitted By : Mutlu DEMİREL Group: 3

MATERIALS:

Ashless Paper , , HcL , Water , , Bunsen Burner , Methyl Orange, , Erlenmayer Flask , , Porcelain Crucibles , Graduated Cylinder , Furnace

PURPOSE:

In this experiment we calculated the weight and % of the sample ,

METHOD:

Gravimetric Analysis

THEORY:

The gravimetric determination of iron in soluble salt is done by converting all iron to , precipitating as a ferrichydroxide and igniting it to . The solubility of ferrichydroxide is very low and therefore quantitative precipitation can be achieved even in acidic solutions of ph up to 4. However , the precipitate is gelatinous and can not be filtrated through sintered glass crucibles because the pores of the crucibles are easily clogged with these types of precipitate. Therefore the precipitate has to be filtered through a filter paper. If the air oxygen is not sufficent , the compound may change to or even metallic iron by carbon from filter paper or reducing gases thar may firm when washing the filter paper.

PROCEDURE:

5 g sample was added 1 ml Hcl and diluted to 250 ml. Then pulled filter paper and 2-3 drops of was added to this solution. After heating just to boil , 3 drops of methyl orange and was added to the solution. After that the solution solution was allowed to precipitate. When the supernatant was become clear , precipitate was allowed to coalugate an filter pulp for 15-30 minutes. Later the solution filtrated and washed with hot wash liquid .After testing the fresh portion filtrate with the filter paper was folded and put into a crucible.Then the crucible was charred off . After that the crucible was ignited at 800-900 in the furnace and weighed. So the weight of was found.

RESULTS AND CALCULATION :

The volume of sample : 5ml

The density of sample : 60 g/L

The molecular weight of Fe : 55.847 g

The molecular weight of : 159.699 g

The mass of crucible : 12.0746 g

The mass of crucible + sample : 12.15.95 g

The mass of sample : 0.0849 g

DISCUSSION:

In this experiment we calculated the weight and % of iron (III) with gravimetric analysis. We used to oxidize ions into before precipitating the solution. Then we added to make the solution alkali and precipitate reaction is obseved as ; While filtering the solution we washed the precipitate with wash liquid and tested the fresh portion filtrate with to observe ions. Washing to completed when no turbitidy is observed. Then the crucible was put on the bunsen burner with low fire. Low fire because of the carbon from the filter paper may reduce to Fe The result of the experiment may have some errors because of the ions that couldn’t be eleminated.Also carbon atoms from the filter paper may reduce to Fe althoug being careful.So the determined weight may not be only pure .

Experiment-1 ( Gravimetric Analysis )

Gravimetric analysis : As the name suggests, gravimetric analysis involves very accurate weighing of a chemical as a means of working out something about that chemical. A common type of gravimetric analysis involves precipitation of a single component (usually an ion) from a known amount of a compound or mixture. This is accomplished by reacting a solution of the test compound with a solution containing an ion that forms an insoluble salt with the component you wish to test for.
…..

In this experiment the sample containing an alkali sulfate is dried, weighed and dissolved in dilute HCl.The precipitation was occur. Barium chloride solution is added in excess to precipitate barium sulfate, and the precipitate is digested in the hot solution. After the precipitate is filtered through a paper filter which is then ignited and completely ashed. From the weight of the sample and weight of the precipitate, the percentage of sulfate in the sample is calculated. The precipitation reaction is the following in below:

Ba2+ (aq) + SO42- (aq) —> BaSO4 (s)

Variations in the acidity, temperature, manner of addition of the precipitant and time of digestion markedly affect the filterability of the barium sulfate precipitate and the extent to which various foreign ions are coprecipitated. Foreign anions such as nitrate, chlorate and chloride are coprecipitated as their barium salts, and the ignited precipitate contains the salt or oxide as an additive impurity. The coprecipitation of chloride can be decreased by slow addition of the precipitant. Since nitrate and chlorate interfere even at low concentrations, they should be removed from the solution before precipitation. Foreign cations such as ferric iron, calcium and, to a lesser extent, the alkali metals are coprecipitated as the sulfates. These are substitutional impurities, and the magnitude of the error depends upon the differences between the weight of the foreign sulfate or oxide and the weight of an equivalent amount of barium sulfate. The presence of ferric iron can produce errors as high as 2% in the determination.

Determination of Calcium

PURPOSE:

             In this experiment, we will determinate the  value of SO4-2 in the sample solution. By this way we will become familiar with basic processes of gravimetric analysis.

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.

           In this experiment we are going to determine the SO4– quantity by precipitating it as BaSO4 for that BaSO4 has a solubility of 0.4 mg/100 g water. We are going to use BaCl2 and as
barium source.

                          Ba+2+SO4-2 à BaSO4(s)

We will separate BaSO4 crystalline precipitate by filtering and wash it. After drying and ignition we’ll weigh the pure BaSO4.

MATERIALS:

v BaCl2 solution (5  g / L).

v HCl solution.

v AgNO3 solution.

v Ashless filtering paper.

v Flask.

v Porcelain crucible.

v Beaker.

v Water.

v Bunsen burner.

PROCEDURE:

v 10 ml of sample was taken in a beaker.

v 1 – 2 drops or 1 ml HCI solution was added.

v This solution was heated until boiling.

v And 100 ml of (1,3 w / v) BaCI2 was heated until boiling an other beaker.

v Then BaCI2  was added quickly  into hot sample.

v Solution was waited and cooled. Until the top of solution became clean.

v After that solution was decanted.

v Solution was filtered and washed with hot water three times.

v Filteted solution was tested with AgNO3 solution. If color does not change.solution was waited one week to dry.

v One week later, filter paper and solid substance were put in  porcelain crucible. and they were chared off about one hour in bunsen burner.

v  Then porcelain crucible was transfered at oven and ignated at 800  0C

v finally,we had only solid (Ba2SO4 (s) ) and weighted.

v Results were recorded.

RESULTS:

Weight of sample and porcelain crucible =    12,7010 g

Weight of porcelain crucible                     =   11,4836 g

Weight of (Ba2SO4 (s) )                              =    1,2174 g

DISCUSSION:

            In this experiment we studied a gravimetrical method; precipitation. This method is so vital for ones who carry out analysis on food sector. It has many advantages as it is easy to carry out, cheap and needs only a little apparatus and reagents. But it has disadvantages as results are very vulnerable to personal or methodic mistakes so less trustable. And it takes nearly one day to get results. So it can be said to be time consuming.

         This method is easy method on the other hand, this method takes so much time.but in food factories, production rate is very important and personal mistakes change results very quickly.