Mixing Barium Chloride to Obtain Pure Barium Sulphate

APPARATUS REQUIRED

i) Beater

ii) Porcelain Basin

iii) Glass rod

iv) wire gauze

v) Test tube

vi) Filter paper

vii) Tripod stand

CHEMICAL REQUIRED

i) Barium Chloride [BaCl₂ solution]

ii) Dilute sulphuric acid (dil H₂S0₄)

iii) AgNO₃solution 

THEORY

Precipitation reaction is a double displacement reaction in which the constituents of reactant are interchanged and hence water insoluble compound is formed from a water soluble compound. When BaCl₂ solution is treated with dil.H₂S0₄ solution in soluble BaSO₄ is obtained as white precipitate.

BaCl₂ + dil. H₂ SO₄ ———-> BaSO₄↓ + 2HCl

[White ppt]

i) The insoluble substance produced during the process is called precipitate. Here,BaSO₄ precipitates.

ii) The constituent which is responsible for precipitation is called precipitant Here, H₂SO₄ is precipitant to occur ionic product [K,p] should be a greater solubility product.

iii) For the precipitation to occurs ionic product, [K,P] should be greater than solubility product [k, P].

iv) During the precipitation reaction the clear solution left above precipitates in called supernatural liquid.

v)The impurities mainly present in this process are chloride (Cl^–) and sulphate [SO₄^—]. The purity of precipitate can be checked by treating the filtrate obtained after washing with AgNO₃ solidon and BaCl₂ solution respectively.

Cl^– + AgNO₃ ———> AgCl ↓ + NO₃ ^–

[Curdy white ppt]

SO₄ ^—+ BaCl₂ ————-> BaSO₄ ↓ + 2Cl^–

[White ppt ]

PROCEDURE

About one test tube full of BaCl₂ solution was taken in beaker and dil. H₂SO₄ was added to it. Half test tube of dilute H₂SO₄ was added to the BaCl₂ solution and was stirred well. Heat the mixture gently such that BaSO₄ settles down completely obtaining a clean solution above. This solution is called  supernatant liquid. The completeness of the reaction was checked by taking little supernatant liquid in the test tube and adding little H₂SO₄. If ppt was obtained then again little dil. H₂SO₄ was added to the mixture. The process continued till no ppt was seen. Then the mixture was filled and it was washed several times with water. The impurities present were tested by using AgNO₃ solution and BaCl₂ solution after each impurity was then taken out and dried in the oven or flame. It was submitted for inspection.

OBSERVATION TABLE

1. Purity test of Cl

S.N.	Experiment	Observation	Inference
1.	Few ml of filtrate was taken in test tube and few drops of AgNO3 solutionwas added.	Curdy white ppt  was obtained	Due to presence of Cl–  ion in precipitate.
2.	After several washing, few ml of filtrate was taken in test tube and few drops of AgNO3added.	white ppt  was not  obtained	Due to absence of Cl–  ion in precipitate.

TEST REACTION

Cl^– + AgNO₃ ————> AgCL ↓+ Cl^–

[Curdy white ppt]

RESULT

Hence, pure and dry BaSO₄ ppt was obtained and was submitted for inspection.

CONCLUSION

In this way, the precipitate of BaSO₄ in pure and dry state can be obtained by precipitation followed by filtration.

PRECAUTIONS

i) Apparatus should be handled carefully.

ii) Acid should be added little by little with constant stirring.

iii) Fast deposition can be done by slight heating.

iv) Impurity tests should be done carefully.

v) Complete ppt. should be checked by carefully.