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Solution


Q.

Read the passage carefully and answer the following questions from (i) to (v):

The phenomenon of the existence of an element in two or more physical forms within the same physical state is known as allotropy. Allotropes have similar physical properties but they differ in chemical properties. In crystalline form, Carbon occurs as graphite, diamond, and fullerenes. Diamond is the hardest natural substance known and is used in cutting marbles, granite, and glass. Graphite is a greyish black and opaque substance, lighter than a diamond with comparatively low density. Graphite has a sheet-like structure having hexagonal layers. One layer slides over the other layer due to weak forces and hence it is soft to touch and breaks easily. Graphite is also used as a lubricant.

 

(iv) Identify the incorrect statement(s):

I. Diamond is the hardest substance known while graphite breaks easily.
II. Each carbon atom in diamond is bonded to 4 other carbon atoms in a tetrahedral manner to form a giant lattice. All carbon atoms are bonded by strong covalent bonds.
III. Graphite is poor conductor of electricity unlike other non-metals.
IV. In each layer of graphite, each carbon atom is bonded to three other carbon atoms forming hexagonal rings of carbon atoms.
1 I and III  
2 Only III  
3 II and IV  
4 I, II and IV  

Ans.

(2)