Notes and Important Points on Solid State - JEE Main 2015
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(1) Graphite is used as a lubricant because its layers can slide over one another when a shearing force is applied. This is due to the weak van der Waals forces between layers consisting of hexagonal carbon networks. (2) Iron is strongly ferromagnetic because it has four unpaired electrons in its electronic configuration. (3) Ice is lighter than water because ice has a hexagonal crystal structure with hydrogen bonding that leaves almost half the space vacant, whereas water occupies spaces more closely when ice melts.
![(1) Graphite is used as a lubricant. Explain.
Sol:
(1) In graphite, all the carbon atoms are sp2 hybridised.
(2) Each carbon atom is covalently bonded to three other sp2 hybridised
carbon atoms forming σ bonds, while fourth electron in 2pz orbitals is used in
the formation of π bond. This results in the formation of hexagonal rings in
two dimensions.
(3) In graphite, the layers consisting of hexagonal carbon network are held
together by weak van der Waals forces imparting softness.
(4) The layers in graphite can slide over another layer on applying a shearing
force; hence it is used as a lubricant and in lead pencils.
(2) Iron is strongly ferromagnetic. Explain.
Sol:
(1) Iron, 26Fe has electronic configuration, [Ar]18, 3d6, 4s2.
(2) Since Fe has four unpaired electrons, it is strongly ferromagnetic.
(3) Solid ice is lighter than water. Explain.
Sol:
(1) Ice has hexagonal three dimensional crystal structure formed due to
intermolecular hydrogen bonding which leave almost half the space vacant.
(2) The structures of liquid water and solid ice are almost identical.
(3) On melting of ice, some hydrogen bonds are broken and vacant spaces
are occupied by water molecules, and they accommodated more closely.](https://image.slidesharecdn.com/notesandimportantpointsonsolidstate-jeemain2015-140702064656-phpapp02/85/Notes-and-Important-Points-on-Solid-State-JEE-Main-2015-1-320.jpg)
Notes and Important Points on Solid State - JEE Main 2015
- 1. (1) Graphite is used as a lubricant. Explain. Sol: (1) In graphite, all the carbon atoms are sp2 hybridised. (2) Each carbon atom is covalently bonded to three other sp2 hybridised carbon atoms forming σ bonds, while fourth electron in 2pz orbitals is used in the formation of π bond. This results in the formation of hexagonal rings in two dimensions. (3) In graphite, the layers consisting of hexagonal carbon network are held together by weak van der Waals forces imparting softness. (4) The layers in graphite can slide over another layer on applying a shearing force; hence it is used as a lubricant and in lead pencils. (2) Iron is strongly ferromagnetic. Explain. Sol: (1) Iron, 26Fe has electronic configuration, [Ar]18, 3d6, 4s2. (2) Since Fe has four unpaired electrons, it is strongly ferromagnetic. (3) Solid ice is lighter than water. Explain. Sol: (1) Ice has hexagonal three dimensional crystal structure formed due to intermolecular hydrogen bonding which leave almost half the space vacant. (2) The structures of liquid water and solid ice are almost identical. (3) On melting of ice, some hydrogen bonds are broken and vacant spaces are occupied by water molecules, and they accommodated more closely.
- 2. (4) In the solid ice, vacant space is more than in liquid water. Therefore the density of ice is less than water (5) Hence ice is lighter than water and ice floats on the surface of water. Find this blog useful. Please give your feedback in the comment box. - Team Ednexa