Available Answers

1. 1.

   Name the following:

   	Name
   a] A hydrocarbon containing - six atoms of hydrogen.
   b] An organic acid containing - carbon.
   c] An inorganic acid containing - carbon.
   d] Two crystalline forms of carbon, occurring in the free state.
   e] An impure form of carbon - which occurs in the free state.
   f] A carbon containing mineral deposit - below the earth's crust.

2. 2.

   Complete the definition of 'allotropy' by striking out the incorrect word.

   Allotropy is the existence of an element / compound in more than one physical form having same / different physical properties but the same graded chemical / physical properties.

3. 3.

   Name the following:

   	Name
   a] A non-metal other than carbon which exhibits allotropy.
   b] A crystalline form of carbon, other than - diamond & graphite.
   c] Two amorphous or micro-crystalline forms of carbon, other than - charcoal or lampblack [soot].
   d] The amorphous form of carbon [charcoal) other than - sugar charcoal & wood charcoal.

4. 4.

   The diagram below shows a crystal lattice of diamond & graphite.

   

   State which of the two allotropic crystalline form i.e. diamond or graphite - shows the following crystal structures.

   Crystal structure	Diamond / graphite
   a] Crystal is - octahedral.
   b] Crystal lattice is built from a - hexagonal unit.
   c] Carbon atom is linked to four other carbon atoms by - covalent bonds.
   d] Has a stable & rigid crystal lattice.
   e] Shows covalent bonds directed towards the - apices's of a regular tetrahedron.
   f] Layers are arranged in parallel & are held together - by weak forces.
   g] Shows absence of - free electrons in the crystal.

5. 5.

   State whether the following statements are true or false - if false write the correct statement.

   1. Diamond occurs naturally embedded in hard rock - found in many par# of the world.
   2. Graphite may be prepared artificially by subjecting pure carbon to - high temperatures & pressure.
   3. The shape of a crystal of diamond is a two dimensional - six sided crystal.
6. 6.

   Give reasons for the following - pertaining to properties of diamond & graphite

   1. A diamond crystal is generally colourless & transparent, but sometimes - has a mild tinge.
   2. Diamond is the hardest natural substance known - while graphite is one of the softest substance known.
   3. The basic structural difference between diamond & graphite - contributes to their differences in densities.
   4. Diamond is a non-conductor of electricity - while graphite is a good conductor.
   5. Diamond is chemically inert & does not react with most chemicals - while graphite is comparatively less inert.
   6. Burning diamond in an atmosphere of oxygen at 800°C - 900°C - proves that it is a pure form of carbon.