131.

Graphite is soft while diamond is hard because

• graphite is in powder form

• diamond has sp² hybridisation but graphite has sp³ hybridisation

• graphite is in planar form while diamond is in tetrahedral form

• graphite is covalent and diamond is ionic

The hardest substance is

• iron

• steel

• diamond

• graphite

Which of the following statements is incorrect regarding graphite?

• The structure of graphite· is two dimensional sheet like consisting of a number of benzene rings

• The structure of graphite is more compact than that of diamond.

• Graphite fibres embedded in plastic material form high strength, light weight composites

• Graphite cleaves easily between the layers

Carborandum is

• Al₂O₃

• AlCl₃

• CuCO₃

• SiC

In which of the following structure the number of shared O-atom per tetrahedrom is two and half?

• Pyroxene chain silicate

• Amphibole chain silicate

• Cyclic silicate

• Sheet silicate

CH₃CHCl₂, on hydrolysis, will give

• CH₃CHO

• CH₃COOH

• CHCl₃

• CH₃CH₂OH

Which of the following statements is correct with respect to the property of elements with increase in atomic number in the carbon family (group 14)?

• Their metallic character decreases

• The stability of +2 oxidation state increases

• Their ionization energy increases

• Their atomic size decreases

Aluminium vessels should not be washed with material containing washing soda since:

• washing soda is expensive

• washing soda is easily decomposed

• washing soda reacts with Al to form insoluble aluminium oxide

• washing soda reacts with Al to form soluble aluminate

Quartz is an example of

• cyclic silicate

• chain silicate

• frame work silicate

• sheet silicate

Silicon is an important constituent of

• alloys

• vegetables

• animals

• rocks