Monday, 20 April 2020

1st year Chemistry Chapter 2 Short Questions Notes.

1st year Chemistry Chapter 2 Short Questions Notes.
Looking for the 11th class Chemistry chapter 2 Experimental Techniques in Chemistry notes? Here we have shared the 1st year Chemistry Chapter 2 Short Questions Notes.

01. Why is there a need to crystallize the crude product?
 The crude product has many soluble and insoluble impurities in it. Insoluble impurities can be separated by filtration and soluble impurities can be separated by crystallization.

 02. A water-insoluble organic compound aspirin is prepared by the reaction of salicylic acid, acetic acid, and acetic anhydride. How will you separate the product from the reaction mixture?
 The product is insoluble in water hence it can easily be separated by filtration. The reaction mixture is added to cold water. Aspirin crystallize out which can be filtered easily.
 03. A solid organic compound is soluble in water as well as in chloroform. During its preparation, it remains in the aqueous layer. Describe a method to obtain it from this layer.
 The solvent extraction technique is used to separate it. Take the reaction mixture in a separating funnel. Add some amount of carbon tetrachloride in it and shake it well. Separate the carbon tetrachloride layer. Now evaporate the carbon tetrachloride to get the organic substance.
 04. In the solvent extraction technique, why repeated extraction using a small amount of solvent is more efficient than using a single extraction with a large volume of solvent?
 Repeated extractions using small portions of solvent are more efficient because more amount of product is extracted. Actually, solvent extraction is a distribution process and is controlled by distribution law. A solute distributes itself between two immiscible solvents occur in a fixed ratio and is given by distribution coefficient:

 KD = conc. of solute in one phase / conc. of solute in other phases

 Small portions of fresh solvent have zero Conc. of solute in it. The distribution co-efficient favors the solute Conc. in the fresh solvent. Thus, repeated extraction using small portions of the solvent is more efficient.
 05. How does a Gooch Crucible increase the rate of filtration?
 Gooch Crucible is made up of porcelain and has a perforated base covered with a filter paper or asbestos mat. The rate of filtration is increased by the suction filtering apparatus.

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