Chemistry 1st and 2nd sem important question with answer aktu

Que1:- Explain why p-nitrophenol is more soluble than o-nitro phenol in water.

Ans:- In p- nitrophenol intermolecular hydrogen bond forms with a water molecule and in o-nitrophenol there is no possible intersection of hydrogen bond formation with water molecule hence p-nitrophenol is more soluble than o-nitrophenol.

 

Que:-2 Explain acetone is more volatile than alcohol.

Ans: Alcohol has strong hydrogen bonding b/w each other which makes it harder to vapourize. In acetone, weak Vander Waal’s forces exist b/w atoms and it boils at very low temperature hence acetone is more volatile than alcohol.

 

Que.3- What is polymerization?

Ans. The process of joining large number of simple molecules to form huge polymer molecules is known as polymerization.

 

Que.4- Define the term ‘monomers’.

Ans. Monomer is the simple chemical substance of low molecular weight which can be converted into a polymer and the molecules of monomer has at least two easily reacting position.

 

Que.5- Define and explain polymer.

Ans. A polymer is defined as the substance having very high molecular weight and is made by joining of large number of simple molecules . Therefore, the polymer molecules have certain structural unit repeating large number of times.

 

Que.6-Explain why Teflon is a highly chemical reactant?

Ans. Due to the presence of the most electronegative element F in Teflon, there are very strong attractive forces between its different chains. Hence, it possesses extremely high chemical resistance towards most chemicals.

 

Que.7- What are the monomers of Buna-S.

Ans. Monomers of Buna-S are 75% butadiene and 25% styrene at 50 degrees C in the presence of cumene hydroperoxide as a catalyst.

 

Que.8-  What do you understand by polymer blends?

Ans. A polymer blend is the mixture of two or more polymers, having better properties than the component polymer. For making a polymer blend it is essential that they are compatible with each other.

 

Que.9- Classify the polymer on the basis of tacticity.

Ans. i. Isotactic polymer ii. Atactic polymer iii. Syndiotactic polymer

 

Que.10-  Classify the polymer on the basis of a number of monomers.

Ans. i. Homopolymer    ii. Copolymer

Que:  Write down the important postulates of the molecular orbital theory.

 

Ans. A molecular orbital is constructed by the combination of two atomic orbital and the method is known as (LCAO) Linear combination of Atomic Orbitals. The important postulates of the molecular orbital theory are:

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Atomic Orbitals of comparable energy and proper symmetry combine together to form molecular Orbitals.

●The movement of electrons in a molecular orbital is influenced by all the nuclei of combining atoms.

●The number of molecular orbitals formed is equal to the no. Of combining atomic orbitals.

●When two atomic orbitals combine together two molecular orbital are formed.

One molecular orbital possess higher energy than corresponding atomic orbitals and is called Antibonding molecular Orbital other than lower energy called Bonding Molecular orbital.

 

The bonding of MOs are represented by π,sigma etc.

While

Antibonding MOs are represented by π*, sigma* etc.

               

 
 

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