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Experiment 7
Experiment 7
Aim of the Experiment
Aim of the Experiment
Identification of a given Inorganic Salt Mixture
Principle
Principle
Qualitative analysis involves the detection and identification of acidic and basic radicals present in inorganic salts. Inorganic salts are formed by the reaction of acids and bases or acidic oxides with a base or basic oxides.
Most of the inorganic compounds are crystalline solids they have defined geometrical shapes. Usually, they consist of oppositely charged particles or ions called radicals.
In the salt analysis, two fundamental principles of great use
1. Solubility Product
2. Common Ion Effect
1. Solubility Product:
1. Solubility Product:
Solubility product is defined as a product of ion concentrations elevated to a power equal to the number of occurrences of ions in an equation representing electrolyte dissociation at a given temperature when the solution is saturated. Under all conditions, the solubility product is not the ionic product, but only if the solution is saturated.
2. Common Ion Effect:
2. Common Ion Effect:
The phenomenon that suppresses the degree of dissociation of any weak electrolyte by adding a small amount of strong electrolyte that contains a common ion is called the common ion effect. For example, by adding a strong electrolyte sodium acetate containing common acetate ion, ionization of weak electrolyte acetic acid is suppressed.
Materials required
Materials required
1. Test tubes, 2. Boiling tubes, 3. Test tube holder, 4. Test tube stand, 5. Corks, 6. Filter paper,7. Delivery tube,8. Reagents
Procedure
Procedure
I. Preliminary Test
State
Colour
Solubility in H2O
Heating in dry test tube
II. Dry Test for Cations
Charcoal cavity test
Flame test
Borax bead test
NH4+ radical test
III. Dry Test for Anions
Substance + dil. H2SO4 + Heat
Substance + conc. H2SO4 + Heat
Substance + conc. HNO3 + (NH4)2MoO4
Statement: From the above dry tests the possible cations are ____________________ and possible anions are _______________________
Preparation of Original Solution: _____________________________________________
Transparent, aqueous solution of salt is known as original solution and it is prepared by dissolving slat/mixture in suitable solvent. To prepare original solution, following solvents are used strictly in the order given below:
(i) Cold water, (ii) Hot water, (iii) Dilute HCl, (iv) conc. HCl
To prepare original solution small quantity of substance is shaken with cold, distilled water. It substance dissolves, whole substance is dissolved in water to prepare original solution. If substance remains insoluble then, mixture is heated and solubility is tested.
If substance is insoluble in hot water also then a few drops of conc. HCl are added.
If substance remains insoluble in dil. HCl also, then we try to dissolve in dil. HNO3.
If substance does not dissolve in the solvents used in above steps, then it is dissolved in conc. HCl. If it remains insoluble even in conc. HCl, then a paste of substance and conc. HCl is made in a porcelein dish and this mixture is heated till it becomes semi-solid. Again conc. HCl is added to make paste and is heated again to get a semi-solid. The procedure is repeated twice or thrice and semi-solid thus obtained is dissolved in distil water. The solution is filtered and filtrate is as original solution. If some insoluble part is obtained that is neglected and is not used. The filtrate obtained as original solution is necessarily diluted with water.
IV. Wet Test for Anions
V. Wet Test for Cations
VI. Equations for Cations
VII. Equations for Anions
Mixture of Nitrate and Nitrite.mp4Chromium Conformative test.mp4Result
Result
1. The given salt contains ________anion and ________________cation.
Conclusion
Conclusion
1. The given salt contains ________anion and ________________cation.
Questions
Questions
Explain what are buffers.
What is solubility? How does it affect qualitative analysis of salt?
Developed by
Developed by
Dr. Rajni Pania,
Assistant Professor, Chemistry,
rajni.pania@gsfcuniversity.ac.in
Ms. Khyati Joshi
Teaching Assitant , Chemistry
khyati.joshi@gsfcuniversity.ac.in
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