Question

The correct statement among the following is -

1) linear polymers have high melting point than cross linked polymer with the same molecular mass.

2) linear polymer is less dense than branched polymer.

3) low density polyethylene is formed due to the high linearity of the structure .

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Answer 1

$\huge\underline\bold\red{Ans}$

2) linear polymer is less dense than branched polymer

Answer 2

The correct statement among the following is :-

➙ linear polymers have high melting point than cross linked polymer with the same molecular mass.

$\tt \orange {Explanation:-}$

The polymers in which the constituent monomeric units are joined to form long straight chains are called linear polymers or straight chain polymers.

In such polymers, the polymeric chains stack over one another and form well packed structure .

Due to this close packing , they have high density, high tensile strength and high melting point .

If the polymer chain has no branches, they pack close to each other and the material has high density.

High density polythene (HDPE) is a linear polymer.

$\bf \pink {Hence , \: Statement \: 'A' \: is \: correct.}$

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Lets study the fault in other statements which were given :-

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STATEMENT 2 :- linear polymer is less dense than branched polymer.

Branched chain polymer are those which have side chains attached to main chain, which is the linear chain .

Due to this branching , Compact packing is not possible.

Thus , they have low density, melting point and tensile strength.

Low density polythene (LDP.E) is a branched chain polymer.

If the polymer chain have lot of branches, then the chains cannot pack together as closely. Thus, the material has low density.

$\bf \red { Hence, \: Statement \: 'B' \: is \: incorrect.}$

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STATEMENT 3 :- low density polyethylene is formed due to the high linearity of the structure .

In cross linked polymers , adjacent polymeric chains link through side chain to form a three dimensional network.

This makes the whole structure more rigid and less elastic.

Long chains get tangled up in each other and stick together far more than short chains. This means that polymers made of long chain molecules have higher melting points than those made of short chains.

Shorter molecules can pas.s over each other more easily so the materials made of these molecules are softer and more 'squishy'.

$\bf \purple {Hence, \: Statement \: 'C' \: is \: incorrect.}$