IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

savvej

more tha n one option correct.
which of the following are true:
(1) Van der waals forces are responsible for formation of molecular crystals
(2) branching lowers boiling points of isomeric organic compounds due to vander waals forces of attraction
(3)In graphite van der waals forces act between the carbon layers
(4)In diamond van derwaal forces act between the carbon layers.

plz tell me the reason of which ever option is correct.and also examples.

master_purav

I think c and b are correct.

For b, look..

Suppose you have unbranched structure, then it would be like this:
---------
--------
--------

Now you have a branched structure,

---- -----
l
---------
l

As you can see the molecular layers have gone far apart in case of branched isomers. So Van Der Waal's force becomed less effective. (There can be no other force of interaction between the two layers)

And for c>

c is sp2 hybridized in graphite. So all orbitals are involved in bonding. Graphite has planar hexagonal structure and so Van Der Waal's force exists between the layers.....

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