SOLUBILITY TEST

Aim: To determine nature of given compound using solubility test.


Requirements: Beaker, Solvents , compound, Test tubes , Testtube stand , glassrod, Molisch regent , litmus paper.


Procedure:

1)Take some amount of sample dissolve it in the solvent.

(Solvents used are water, NaOH, NaHCO3 , HCl.)

2)Check the given compound is soluble in which solvent.

If it is soluble in HCl- the given compound is water insoluble basic,

NaHCO3 then water insoluble strong acid, 

NaOH then water insoluble weak acid,

In water the compund is water soluble neutral/acidic/basic.


Theory:-

When mixture of definite quantity of given solute and specific amount of given solvent forms a homogeneous amount liquid the former is said to be soluble in the latter.

The study if solubilty behavior of an unknown substance in various liquids ie water , sodium hydroxide, sodium hydrogen carbonate and HCl.


1) compund +H2O---

▪︎If it solublizes in water then perform litmus test


•If blue litmus turns red it is water soluble acidic


•If red litmus turns blue it is water soluble basic


•If no change it is water soluble neutral then

Proceed for molisch test


-If violet ring form the test is positive and compound is carbohydrate.

-If not then compund is water solube netural salt.


▪︎Not soluble in water proceed for other solvent.


2) Compound+ NaHCO3-----

▪︎Soluble then presence of water insoluble strong acid


•Strong acids: Strong acid e.g. benzoic acid gives effervescence with NaHCO3
Hence, effervescence on addition of NaHCO3 to binary mixture indicates presence of strong acid

Water-insoluble strong acids (e.g. phthalic acid, benzoic acid) will give effervescence and dissolve in saturated NaHCO3


•Weak acids:Weak acids such as phenols do not react with saturated NaHCO3 since NaHCO3 is a weak base.

▪︎ if not soluble proceed for NaOH

3)Compound + NaOH-----

▪︎ If Soluble then water insoluble weak acid.

•Strong and weak acids: Both strong and weak acids react with NaOH to form water soluble salts. Individual compounds can be regenerated using cone. HCI. Only water insoluble acids regenerate but not  water-soluble ones


▪︎ if insoluble in NaOH proceed for HCl

4) Compound+ HCl------

▪︎It is water insoluble base.



Conclusion

The given compound if soluble in

HCl - water insoluble basic,

NaHCO3 -water insoluble strong acid, 

NaOH -water insoluble weak acid,

H2O-water soluble neutral/acidic/basic.



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