determination of sulfate as barium sulfate

University Of Karachi

CHEMICAL PROCESS TECHNOLOGY

(Practical file)

Syed Saad AhmedB-0933040B.E 3rd Year

Chemical Engineering

Submitted To:Ma’am Khehkashan

CHEMICAL PROCESS TECHNOLOGY 2012

Experiment no. 2

OBJECT:

Determination of sulfate as barium sulfate

APPARATUS AND REAGENTS:

250 ml beaker. Bunsen burner, Water bath, Muffle furnace. Crucible. 0.2 M barium chloride. Potassium sulfate. Concentrated hydrochloric acid.

THEROY:

A sample containing an alkali sulfate is dried, weighed and dissolved in dilute HCl. Barium chloride solution is added in excess to precipitate barium sulfate, and the precipitate is digested in the hot solution. 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:

Ba(aq)2+¿+SO4(aq)

2−¿⟶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 co-precipitated. Foreign anions such as nitrate, chlorate and chloride are co-precipitated as their barium salts, and the ignited precipitate contains the salt or oxide as an additive impurity. The co-precipitation 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.

PROCEDURE:

Weight out accurately 0.5 grams of Potassium sulfate and transfer it to 250 ml beaker. Dissolve the solid in about 25 ml of water and add 0.5-1 ml of concentrated HCl and dilute to about 200 ml. Heat the solution to boiling, add drop wise 15-20 ml of 0.2M BaCl2.H2O. Stir the solution constantly during the addition. Allow the precipitate to settle for 4-5 minutes. Then test the supernatant liquid for complete precipitation by adding a few more drops of Barium chloride solution. If a precipitate is formed add slowly a further 3-5 ml of the BaCl2 solution. Allow the

2 Prepared By: Syed Saad Ahmed |


precipitate to settle as before and test again. Repeat this operation until an excess of BaCl2 is present. Keep the covered solution hot, but not boiling for an hour on water bath in order to allow time for complete precipitation. Filter off the precipitated barium sulfate through a weighed sintered glass crucible no. 4 and wash it with hot water until the chloride reaction of the washing is negative. Such that the precipitate dry on the pump for 3 minutes. Ignite the precipitate in a crucible for 15 minutes at 600oC in the furnace.

CALCULATION:

Calculate amount of sulfate in Barium Sulfate:

Weight of empty crucible = 14.20 g

Weight of empty crucible + BaSO4 = 14.78 g

Weight of precipitate (BaSO4) = 0.58 g

Molecular weight of BaSO4 = 233.43 g

Amount of SO4 in BaSO4 = 96.062 g

⇒0.5 gmof K 2SO 4→0.58 gmof BaSO4

⇒233.43 gmof BaSO4→96.062gmof SO4

⇒1 gmof BaSO4→96.062233.43

gmof SO4

⇒0.58 gmof BaSO4→96.062233.43

×0.58 gmof SO4

⇒0.58 gmof BaSO4→0.2386 gmof SO4

RESULT:

Amount of sulfate in 0.58 gm of BaSO4 is found to be 0.2386 grams

THEORETICAL AMOUNT OF SO4 IN K2SO4:

Molecular weight of K2SO4= 174.259



Molecular weight of SO4 = 96.062

⇒174.259 gmof K 2SO4 produces→96.062gmof SO4

⇒1 gmof K 2SO4 produces→96.062174.259

gmofSO4

⇒0.5 gmof K 2SO 4 produces→96.062174.259

×0.5 gmofSO4

⇒0.5 gmof K 2SO 4 produces→0.2758gmofSO4

PRACTICAL OBTAINED YIELD:

Practical yield is found to be = 0.2386 grams

% yield= practical yieldtheoritical yield

×100

¿ 0.23860.2758

×100

¿86.51%

DISCUSSION:

Barium sulfate (BaSO4) is the barium salt of sulfuric acid. In nature, barium sulfate is found as crystals. Barium sulfate is practically insoluble in water, acids (an exception being hot concentrated sulfuric acid) and bases. Due to its extremely low water solubility, barium sulfate, as compared to other barium compounds, is non-toxic.


determination of sulfate as barium sulfate

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