To separate the components of a mixture of two insoluble solids (one being soluble in dilute acids)

APPARATUS REQUIRED

i) Beater

ii) Filter stand

iii) Funnel

iv) Filter Paper

v) Test tube

vi) Burner, tripod stand and wire gauge

CHEMICAL REQUIRED

i) Mixture of sand and CaCO₃

ii) BaCl₂ solution.

iii) Dil HCL

iv)Na₂CO₂ solution

v) AgNO₃ solution.

THEORY

Sand and calcium carbonate are soluble in water. So, dilute hydrochloric acid is taken as solvent because calcium carbonate is soluble in dilute hydrochloric acid. The mixture is filtered and is obtained as residue with sodium carbonate solution to recover calcium carbonate.

Heterogeneous mixture:

The mixture in which the mixing component can be seen by our naked eye  is known as heterogeneous mixture.

Precipitation reaction:

The double decomposition reaction usually between two solution resulting in the formation of an insoluble substance is known as precipitation reaction.

Precipitate:

The insoluble solid which is obtained during precipitation reaction is known as precipitate.

Filtration:

The process of separating the insoluble component from the solution of the soluble component with the help of filter paper is known as filtration.

Filtrate:

The clear liquid which is left after filtrate is known as filtrate.

dil. 2 HCL

Sand + CaCO3 —————————–>Sand + CaCl₂ + CO₂ + H₂O

     (S)        (aq)            (g)

CaCl₂ + Na₂CO₃ —————————-> CaCO3 + 2NaCl 

(aq.)        (aq.)     (s)              (aq) 

PROCEDURE

Above 2 gram of mixture of sand and calcium carbonate was taken in a small beaker and dropwise dil. HCL solution was added fill the complete appearances of CO₂ ceases. The solution was filtered. The sand was washed 3-4 times with water to remove chloride ion the sodium carbonate  solution was added to the filtrated till the white ppt of calcium carbonate was obtained. The ppt of calcium carbonate was obtained. The ppt of calcium carbonate is filtered and washed with water. The purity of the solution was tested by BaCl₂ solution. The ppt of C₂CO₃ and sand was dyed over burner and submitted to the teacher.

OBSERVATION TABLE

S.N.	Experiment	Observation	Inference
1.	Sand washed water was tested with AgNO3 solution.	Curdy white ppt was observed.	Presence of Cl– .
2.	After washing the sound sand water was treated with an AgNO3 solution.	No ppt was observed.	Absence of Cl– .
3.	CaCO3ppt washed water was treated with AgNO3 solution .	White ppt was observed.	Presence of Cl– .
4.	After washing CaCO3 ppt washed water was treated with AgNO3 solution.	No any ppt was observed.	Absence of Cl– .
5.	CaCO3 ppt washed water was treated with BaCl2 solution.	White ppt was observed.	Presence of soluble CO3 –
6	After wasting, CaCO3 ppt washed water was treated with BaCl2 solution.	No any ppt was observed .	Absence of soluble CO3 –

TEST REACTION

AgNO₃ + Cl^– —————-> AgCl ↓ + NO₃^—

(Curdy white ppt)

BaCl₂ + CO₃– ————–> BaCO₃ + 2Cl^–

                                               (white ppt)

RESULT

Pure sand and pore CaCO₃ were separated from the mixture by precipitation, filtration and drying.

CONCLUSTON

The two water insoluble components can be separated by dissolving dilute HCl by precipitation.

PRECAUTION

i) All the apparatus should be handled carefully.

ii) Dilute H₂SO₄ should not be used since insoluble CaSO₄ coils are formed.

iii) The precipitation of CaCO₃ should be complete.