UNIT# 12
CARBON, SILICON AND
THEIR COMPOUNDS
|
Q# |
Question |
Year |
|
Q# 01 |
Differentiate between Diamond and graphite |
[2014] [2011] [2010] |
|
Q# 02 |
Write
three uses of graphite |
[2015] |
|
Q# 03 |
Describe crystalline and amorphous forms of Carbon |
[2016] [2009] [2005] |
|
Q# 04 |
Write
note on Silica gel |
[2013] |
|
Q# 05 |
Define
water glass and write its two uses |
[2012] |
Q. Write few lines on Carbon.
INTRODUCTION
TO CARBON
Carbon contains four
electrons in its outer most shell. So it is placed in the group IVA of the periodic
table. Its symbol is ‘C’. It is non-metal.
Q. Describe the occurrence of
Carbon.
OCCURRENCE
OF CARBON
Carbon is the second most
abundant element. It occurs in plants and animals tissues, combined with H and
O.
The major source of carbon is
coal. The amount of carbon in coal depends upon the stage of conversion of
plant material into coal.
It also occurs in metal
carbonates in the earth crest rocks. The most common carbonate rock is 9CaCO3)
which occurs as marble.
It also occurs as oxide form
in atmosphere, carbon mono oxide and carbon dioxide.
In
the Free State
Carbon also occurs in the
following states.
Crystalline form:
1. Diamond
2. Graphite
3. Bucky balls
Amorphous form:
1. Lamp black
2. Wood charcoal
3. Animal charcoal
4. Gas carbon
Q. Define Allotropy and
Allotropes.
ALLOTROPY
The existence of two or more forms
of the same elements in the same state is called allotropy and different forms
and known as allotropic modification or allotropes
ALLOTROPES
The allotropes are the
different forms of the same element in the same state. Allotropes possess same
chemical properties but have different physical properties
Q. Describe the allotropic forms
of Carbon.
ALLOTROPIC
FORMS OF CARBON
There are three solid forms
of carbon
a. Diamond
b. Graphite
c. Bucky balls
Q. Describe the properties and
uses of Diamond.
DIAMOND
It is naturally found South
Africa, Australia, Brazil and India.
PROPERTIES
1. It is hardest material
substance.
2. It is the nonconductor of heat
and electricity.
3. It is colorless and
transparent solid.
4. The color of diamond is due
to the impurities.
5. Its melting point is very high about 35000
C.
USES
1. It is used for grinding and
cutting the hard substance such as glass, pottery and rock
2. It is used as a dye drawing
metal into fine wire used as lamp
filament and so on
Q. Describe the properties and
uses of Graphite.
GRAPHITE
It is naturally found in
China, Brazil, and Canada etc.
PROPERTIES
1. Graphite occurs naturally as
plumage an opaque black solid
2. Graphite is less dense then
diamond
3. It is soft and greasy to feel
4. It is of dark grey color
crystalline solid with dull metal luster
5. It is more reactive then
diamond
6. It is good conductor of heat
and electricity
7. Its melting point is about
30000 c
USES
1. It is used in preparation of
electrodes
2. It is also used as a
lubricant
3. It is used as a conductor
Q. Describe the properties and
uses of Bucky balls.
BUCKY BALLS
Buckminster fllurence or
commonly Bucky balls are the crystalline form of Carbon that exists in a ball
like structure with pentagonal and hexagonal arrangement of carbon atoms.
PROPERTIES
1. It has a highly symmetric
structure.
2. It can be dissolved in
organic solvents.
3. Carbon atoms are joined as making
pentagons and hexagons as are found in a football.
USES
1. It is mixed with oil and used
as lubricants.
2. It is dissolved in organic
solvents which are used for many purposes.
3. It is used as semi-conductor.
Q. Describe four stages of coal.
There are four stages of coal.
1. Peat
2. Lignite
3. Bituminous coal
4. Anthracite
Q. What is Coke? Write its uses.
COKE
Coke is produced by the
destructive distillation of bituminous coal to very high temperature about
(130000 C) in the absence of air.
USES
1. Coke is used as fuel for home
and industries
2. It is also used as reducing
agent in the extraction of metals especially iron
3. It is also used for the
manufacture of calcium carbide
Q. What is Charcoal? Write its
uses.
CHARCOAL
Charcoal is porous and is a
good absorbent. It is so full of air that it floats in water. Charcoal is of
various types.
USES
1. It is mainly use ion domestic
fuel
2. It is used in gas masks for
absorbing poisonous gas
Q. What is Animal Charcoal? Write
its uses.
ANIMAL
CHARCOAL
It is the residue when bones
and animals refuses are heated without air. The process is called destructive
distillation of animal bones’
USES
1. It is used in refining of
brown sugar
2. It is also used in
decolonization of petroleum jelly
3. It is also used for
purification of noble gas
Q. Describe the Physical
Properties of Carbon.
PHYSICAL
PROPERTIES OF CARBON
1. All crystalline and amorphous
form of carbon except diamond are grayish black.
2. All of them are tasteless and
colorless
3. Their melting points are very
high (about 5000oC)
4. They are not soluble in
water, petrol, acid and alkaline
Q. Describe the Chemical
Properties of Carbon.
CHEMICAL
PROPERTIES OF CARBON
Chemically carbon is not very
reactive element
1) COMBUSTION
All forms of carbon burn in
the excess of air (O2) to produce carbon dioxide (CO2)
gas
C + O2 ® CO2
H = -394KJ/mol
The combustion reaction is
highly exothermic. Combustion is incomplete carbon mono oxide
2C + O2 ® 2CO
2) COMBINATION REACTION
Carbon combines directly with
other elements such as Hydrogen, Sulphur, calcium, aluminum at very high
temperature to form addition products
C + 2H2 ® CH4 [Methane]
C + 2S ® CS2 [Carbon di sulphide]
2C + Ca ® CaC2 [Calcium carbide]
3C + 4 Al ® Al4C3
[Aluminum
carbide]
3) AS REDUCING AGENT
Carbon is a powerful reducing
agent because it has greater affinity for oxygen. It reduces many metals oxide
and other oxide into free metal, reduction forms CO and CO2.
ZnO + C ® 2 Zn + CO2
2 PbO + C ® 2
Pb + CO2
Fe2O3 +
3 C ® 2 Fe +3 CO
2 Cu2O + C ® 2
Cu + CO2
Cu2O + C ® 2
Cu + CO
H2O + C ® CO + H2
CO2 + C ® 2 CO
4)
REACTION WITH STRONG OXIDIZNG
AGENT
When carbon is heated with
concentrated H2SO4, HNO3, It is oxides to CO2.
C + 2 H2SO4
® 2
H2O + 2 SO2 + CO2
C + 4 HNO3 ®
2 H2O + 4 NO2 + CO2
Q. Describe the uses of Carbon.
USES
OF CARBONS
1. Diamond is uses as germs.
2. Graphite is used as
lubricants.
3. Coal and coke are used as
fuel.
4. Charcoal is used in gas marks
for absorbing poisonous gases.
5. It is used as filler in tires
to increase their strength.
Q. Define Catenation.
CATENATION
The
property of an element to form a long chain is called catenation. It is the
most important property of Carbon and Silicon.
Q. Describe the occurrence of
Silicon.
OCCURENCE
1. Silicon does, not occur in
the Free State, although silicon is widely distribute in nature.
2. In combine state it occurs
mainly as silicon IV oxide, SiO2 (silica)
3. The less pure forms are sand,
kieelgar agate etc.
4. The pure crystalline form is
quartz and flint.
|
S# |
Name of Silicate |
Formula |
Uses |
|
1 |
Feldspar |
K2OAl2O3.
6SiO2 OR
KAlSi3O8 |
Ceramics,
glass, pottery |
|
2 |
Kaolin
(China clay) |
Al2O3SiO22H2O |
Crockery |
|
3 |
Mica |
K2O.3Al2O3.6SiO2.2H2O
OR KAl3Si3O10 |
Electrical
insulator |
|
4 |
Talc |
3MgO.4SiO2.H2O |
Ceramics |
|
5 |
Asbestos |
CaO.3MgO.4SiO2
OR Ca.MgSi4O12 |
Heat
insulation or fire proofing |
Q. Describe the Preparation of
Silicon.
PREPRATON
OF SILICON
1) Amorphous silicon
Amorphous silicon may be
prepared by heating a mixture of pure dry and sand and magnesium powder in a
fire clay crucible.
SiO2 + 2 Mg ® 2 MgO + Si
Dilute hydrochloric acid then
added.
Mg + 2 HCl ® Mg Cl2 + H2
MgO + 2 HCl ® MgCl2
+ H2O
2) By reduction
When the vapors over heated
sodium or potassium in an insert atmosphere, silicon is produce by reduction.
Si Cl4 + 4 Na ® Si + 4 NaCl
Si Cl4 + 4 K ® Si
+ 4 KCl
3) Crystalline silicon
Crystalline silicon is
prepared by heating crushed coke (carbon) and an excess of sand in an electric
for mace. This product is not very pure but suitable for use in always.
SiO2 + 2 C ® Si
+ 2 CO
Q. Describe the Physical
properties of Silicon.
PHYSICAL
PROPERTIES OF SILICON
1. Silicon is no-volatile solid.
2. It melting point is 1410 and
boiling point is 2600.
3. It is poor conductor of
electricity.
4. Amorphous silicon is brown in
colored with specific gravity 2.35
5. It is in soluble in most of common
solvent like water but it dissolve in hydrochloric acid.
Q. Describe the Chemical
properties of Silicon.
CHEMICAL
PROPERTIES OF SILICON
1) Reaction with alkalis
Si
+ 2NaOH + H2O ® Na2SiO3
+ 2H2
2) Reaction with Air
Si
+ O2 ® SiO2
3) Reaction with chlorine
Si
+ 2Cl2 ® SiCl4
4) Reaction with potassium
hydride
Si
+ 2KOH ® K2SiO3
+ 2H2
Q. Describe the uses of Silicon.
USES
OF SILICON
1. Silicon is used in bronze and
steel allays to Increase their strength.
2. They are used as lubricants,
used in paints, varnish and polisher.
3. Silicon is used in
preparation of refractory material such as erasable, fire bricks etc.
4. Very pure silicon is used in
making semiconductor which are of great importance in computer transistor.
5. It also used for making
silicon which are rubber like liquid or solid that are insoluble in water.
Q. What is Silica?
SILICA
(SiO2)
Silica dioxide or silica
occurs naturally in three main crystalline forms.
1. Quartz
2. Tridymite
3. Crystobality
Q. Describe the preparation of
Silica.
PREPARATION
OF SILICA
1.
Silica can be obtained in a hydrated forms, as
gelatinous participated, by warming sodium silicate with can. HCl.
Na2 SiO3
+ 2 HCl ® SiO2 H2O + 2 NaCl
2.
Silica can be prepared by heating silicon in
air or oxygen.
Si + O2 + Heat ® SiO2
Q. Describe the Uses of Silica.
USES
OF SILICA
·
It is widely used in making motors, cement,
concrete and glass etc.
·
Large Quartz crystals are used for lenses of
optical instruments.
·
Powdered Quartz is used in the making of sodium
silicate (Water glass) and silica bricks.
Q. Describe the physical
properties of Silica.
PYSICAL
PROPERTIES OF SILICA
1. Silica exists in a colorless
crystalline form when pure.
2. Silica is a non-volatile
solid.
3. It melts at 15000C.
4. When cooled, it form glass
like solid known as quartz glass.
5. It has giant covalent structure in which
each silicon atom is linked to four oxygen atoms.
Q. Write note on Water glass.
WATER GLASS (SODIUM SILICATE)
Sodium silicates dissolve in
hot water under pressure to form a viscous liquid which is known as water glass
because it looks like ordinary glass.
USES OF WATER GLASS
·
It is used for preservation of eggs.
·
It is used in hardening of artificial stone.
·
Water glass is used for sizing of paper.
·
Water glass is used for fire proofing wood and
textile and for making glue.
·
It is also used as filler in soap industries.
·
It is used for making chemical garden in the
science fair.
Q. Write note on silica gel.
SILICA JEL
Silica
gel is an amorphous and porous form of silicon dioxide (silica), when an acid is added in a
solution of water glass it turns into a jelly like substance, called Silica
Jel.
The chemical formula of
Silica Gel is SiO2.nH2O
USES OF SILICA JEL
·
Silica gel is used as good absorbent.
·
It is used to absorb gases and vapors.
·
Bags of silica gel are used to keep in medicine
pickings to prevent the medicines spoiled by water vapors.
·
It is also used to recover valuable vapors.
Multiple Choice Questions
Choose the correct option for
each of the following statement.
i.
Diamond is used as abrasive
because it is:
a. Hard
b. Soft
c. Cubic
d. Bad conductor of heat
ii.
Silicon is most abundantly
found in:
a. Silica
b. Sodium silicate
c. Silicon carbide
d. Calcium silicate
iii.
Diamond is use in:
a. Jewellery
b. Gems
c. Glass cutting
d. All of these
iv.
All the allotropic forms of
carbon have melting point above:
a. 10000C
b. 2500o C
c. 4000o C
d. 5000oC
v.
Water glass is use for:
a. Manufacturing of soaps
b. Drying air
c. Optical instruments
d. All of these
vi.
The molecular formula of sand
is:
a. SiO
b. SiO2
c. SiO3
d.
Na2SiO3
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