Chem Notes 1st Year Chap 2
Important Question
Q How the desiccators are used for drying of crystals ?
Ans: A safe and reliable method of drying crystals is trough vaccum desiccators. In this process the crystal are spread over a watch glass and kept in the vaccum desiccators for several hours.
Drying Agents: The drying agents used in desiccators are CaCl2 sillica gel or P2O5
Q Why there is needed to crystallize the crude product ?
Ans: When a chemical compound is prepared it is not pure rather a crude product. It is therefore purified by process of crystallization using a proper solvent.
Q Define the sublimation. Why solid iodine during sublimation is directly converted in to vapours ?
Ans: t is the process in which a solid on heating vapourizes directly with out passing trough the liquid state these vapours can be condensed to form solid again.
This technique is frequently used to purify the volatile solids. Examples of the volatile solids are Ammonium Chloride, Naphthalene, iodine, Benzoic acid etc.
Solid iodine has very weak intermolecular forces in crystals. The vapour pressure of solid iodine is very high at room temperature. The solid substances having high vapour pressure undergo the sublimation.
Q How the undesirable colour of crystals is removed?
Ans: The decolourizing crystals may be carried out by boiling the substance in the solvent with sufficient amount of finely devided animal charcoal and then filtering the hot solution. the coloured impurities are absorbed by the animal charcoal and the pure decolorized substance srystallizes out form the filtrate on cooling.
Q What is Rf Value ? Give its units Rf is always less than 1.0 Comment on it.
Ans: It is the specific retardation factor of each components separated from the mixture. It can be calculated as
Rf= Distance travelled by a componant from the original spot
_________________________________________
Distance travelled by the solvent from original spot
Since it is the ratio and cannot have value greater than one as the solute cannot move forward to the solvent front. It is because those solute particles have stronger affinity for the stationary phase compared to the mobile phase.
Q What is the solvent extration ?
Ans: It is an experimental technique in which solute can be separated from the aqueous solution by shaking the solution with a solvent in which the solute is more soluble and the added solvent does not mix the solution Usually it is by shaking the solution and the solvent into a separating funnel which is stop-red.
Q Mention experimental technique which are used to purify substances.
Ans: Following are the various experimental technique which are used for purification of substances
Filtration, Crystalliztion, Sublimation, Solvent Extraction and Chromatography.
Q Write main Characteristics of solvent chosen for crystallization of a compound.
Ans: The solvent is selected on the hit and trial basis by using number of solvents.
An ideal should have following properties
1 It should dissolve a large amount of substances at the higher temperature and only a small amount at room temperature.
2 It should not chemically react with solute.
3 It should not dissolve impurities.
4 It should deposit well formed crystals on cooling.
5 It should be inexpensive or cheaper.
6 It should be safe to use and easy to remove.
Q Define the Chromatography?
Ans: It is an experimental technique by which components a mixture are separated on the basis of their different relative solubilities or affinities in the stationary and mobile phase according to partition co-efficient.
K= Conc. of component in mobile phase
__________________________
Conc. of component in stationary phase
Q Different between the sublimation and Condensation
Ans: Conversion of a solid into vapours with out passing trough a liquid phase state is called subliamtion.
The sublimation whereas conversion of vapours into liquid or solid is called condensation.
Q Define mother liquor ?
Ans: Solution remaining after the formation crystals is called the mother liquor.
Q What are the major steps involved in the crystallization.
Ans: Following are the major steps involved in the crytallization.
Preparation of Saturated solution.
Filtaration of insoluble Impurities
Cooling of hot solution
Collection of crystals
Drying of Crytallized Substances.
Q How the desiccators are used for drying of crystals ?
Ans: A safe and reliable method of drying crystals is trough vaccum desiccators. In this process the crystal are spread over a watch glass and kept in the vaccum desiccators for several hours.
Drying Agents: The drying agents used in desiccators are CaCl2 sillica gel or P2O5
Q Why there is needed to crystallize the crude product ?
Ans: When a chemical compound is prepared it is not pure rather a crude product. It is therefore purified by process of crystallization using a proper solvent.
Q Define the sublimation. Why solid iodine during sublimation is directly converted in to vapours ?
Ans: t is the process in which a solid on heating vapourizes directly with out passing trough the liquid state these vapours can be condensed to form solid again.
This technique is frequently used to purify the volatile solids. Examples of the volatile solids are Ammonium Chloride, Naphthalene, iodine, Benzoic acid etc.
Solid iodine has very weak intermolecular forces in crystals. The vapour pressure of solid iodine is very high at room temperature. The solid substances having high vapour pressure undergo the sublimation.
Q How the undesirable colour of crystals is removed?
Ans: The decolourizing crystals may be carried out by boiling the substance in the solvent with sufficient amount of finely devided animal charcoal and then filtering the hot solution. the coloured impurities are absorbed by the animal charcoal and the pure decolorized substance srystallizes out form the filtrate on cooling.
Q What is Rf Value ? Give its units Rf is always less than 1.0 Comment on it.
Ans: It is the specific retardation factor of each components separated from the mixture. It can be calculated as
Rf= Distance travelled by a componant from the original spot
_________________________________________
Distance travelled by the solvent from original spot
Since it is the ratio and cannot have value greater than one as the solute cannot move forward to the solvent front. It is because those solute particles have stronger affinity for the stationary phase compared to the mobile phase.
Q What is the solvent extration ?
Ans: It is an experimental technique in which solute can be separated from the aqueous solution by shaking the solution with a solvent in which the solute is more soluble and the added solvent does not mix the solution Usually it is by shaking the solution and the solvent into a separating funnel which is stop-red.
Q Mention experimental technique which are used to purify substances.
Ans: Following are the various experimental technique which are used for purification of substances
Filtration, Crystalliztion, Sublimation, Solvent Extraction and Chromatography.
Q Write main Characteristics of solvent chosen for crystallization of a compound.
Ans: The solvent is selected on the hit and trial basis by using number of solvents.
An ideal should have following properties
1 It should dissolve a large amount of substances at the higher temperature and only a small amount at room temperature.
2 It should not chemically react with solute.
3 It should not dissolve impurities.
4 It should deposit well formed crystals on cooling.
5 It should be inexpensive or cheaper.
6 It should be safe to use and easy to remove.
Q Define the Chromatography?
Ans: It is an experimental technique by which components a mixture are separated on the basis of their different relative solubilities or affinities in the stationary and mobile phase according to partition co-efficient.
K= Conc. of component in mobile phase
__________________________
Conc. of component in stationary phase
Q Different between the sublimation and Condensation
Ans: Conversion of a solid into vapours with out passing trough a liquid phase state is called subliamtion.
The sublimation whereas conversion of vapours into liquid or solid is called condensation.
Q Define mother liquor ?
Ans: Solution remaining after the formation crystals is called the mother liquor.
Q What are the major steps involved in the crystallization.
Ans: Following are the major steps involved in the crytallization.
Preparation of Saturated solution.
Filtaration of insoluble Impurities
Cooling of hot solution
Collection of crystals
Drying of Crytallized Substances.
thnks
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteThat's amazing
ReplyDeleteGreat
ReplyDeleteAmazing great
ReplyDeleteAmazing great
ReplyDeleteAmazing great
ReplyDelete