CHAPTER 11- OXYGEN, SULPHUR AND CHLORINE
Q1) how is oxygen industrially prepared from air and water?
ans) industrial preparation: oxygen is obtained on an industrial scale
from air and water.
1)from air:-
(a) air is a mixture of oxygen and nitrogen the ratio by volume being
21:78. the air is liquified by cooling under pressure and the liquid
ait fractionally distilled.nitrogen being morevolatile(boiling
point-196c) escapes out first and oxygen being less volatile (boiling
point -183) is left behind.
(b) oxygen can also be obtained from air by a chemical method. barium
oxide is heated upto 500c in air which combine with the oxygen of air
and is converted into barium peroxide. barium peroxide on heating at
1000c decompose into oxygen and barium oxide.
2BaO+O22BaO2
2)from water:-oxygen is obtained on large scale by electrolysis of water.
2H2O2H2+O2
Q2) what is action of O2 on:-
1) C (2) Ca (3) Al
ans)reaction with non metal:-non metal such as
carbon,sulphur,phosphorus burn in oxygen forming their respestive
oxides.hydrogen burns violently with oxygen to form water.
C+O2CO2
2)reaction with metal:-highly reactive metals such as sodium and
potassium react rapidly with oxygen at low temperature.
2Na+O22Na2O
3)reaction with aluminium:-aluminuim powder burns violently in
oxygen.flash bulbs used in photography contain aluminium foil in an
atmosphere of oxygen.
2Al+3O22Al2O3
Q3) what are oxides?discuss various type of oxide give their
characteristic properties.
ans)oxides:-the binary compounds of the element with oxygen are called oxides.
on the basic of valence number of oxygen they are ordinarily
classified into four main groups,namely:-
1) normal oxide
2) peroxide
3) super oxide
4) suboxide
1)normal oxides:-there are the oxides in which the valence number of
oxygen is -2.
normal oxide are classified into four types.
a)basic oxide:-these oxide react with acid to produced salt and water.
b)acidic oxide:-these oxide react with base to from salt and water.
c)nuetral oxide:-these oxide are neither acid or a base their have no
action on blue or red litmus.
d)amphoteric oxide:-these are oxide which passess the properties of an
acid as well as a base.
2)peroxide:-the valence number of oxygen in peroxide is -1.peroxide
form hydrogen peroxide on reaction with dilute acid. example of
peroxide are sodium peroxide,barium peroxide and hydrogen peroxide.
3)superoxides:-the valence number of oxygen in super oxide in -1/2.
superoxidehave an excess amount of oxygen than normal and superoxides.
4)suboxide:-suboxide have less quantityof oxygen than the normal
oxides,they are unstable and very few suboxide are known. an example
of suboxide is C3O2 which is named as carbon suboxide.
Q4) how is ozone produced? discuss the usefulness of protective layer
of ozone and its deplation
ans)ozone:-ozone,wich has a molecular formula O3, is an allotropic
from of oxygen when an electrical discharge passes through ordinary
diatomic oxygen energy is absorbed and some of oxygen is converted to
ozone.
3O22O3
due to the presnce of this extra oxygen ozone ozone is used for
disinfecting water supplies and large summings poolsthe atomic oxygen
kills any harmful bacteria present because of this propertyozone is
used to sterilise air in confined and crowded spacessuch as
undergroundrailway stations and slaughter houses.
ozone also find applications as a bleching agent for oilswaxes starch
and flour. the atomic oxygen it releases,bleaches the organic dyes
present in these material by oxidizing them.
Q5) how is sulphur extracted by frasch process.
ans)extraction of sulphur:-harmen frasch developed a method for
extractionof sulphur. the basic principle of this method is that
sulphur is method under ground and pumped up to the surface. the
details of the method are describe below.
a bore is made to the deposists of sulphur and three concontric pipes
are sunk into the bore. the outermost pipe (20 cm diometre) is sunk up
to the deposists and the most inner (10 cm diometre) is held a little
above the surface of deposists. super heated wter at 170c under a
pressure of 16 atom is pumped down the outermost pipe.this water melts
the sulphur (m.p 113c) whichcollect in a pool at the bottom. hot
compressed air is blown down the innermostpipe.it forms a foam of
molten sulphur which arises through the amnular space between the
inner most pipe and the next when this foam ofsulphur reaches the
surface it is collected in big wooden basin. after sometimes air
escapes and sulphur solidfies in huge blocks at the bottom of
tanks.sulphur obtained by this process is 99.5 percent pure.
Q6) how is sulphur dioxide prepared in laboratory ?
ans)laboratory preparation:-sulphur dioxide is prepared by heating
copper turning with concentrated sulphuric acid in round bottomed
flask fitted with delivery tube and the gas is collected by upward
displacement of air.
Cu+2H2SO4CuSO4+2H2O+SO2
Q7) what is the reaction of sulphur dioxide on:-
H2O, H2S,FeCl3
ans)reaction with water:-when sulphur dioxide is dissolved in water it
froms sulphurous acid which decompose into its constituent on heating.
SO2+H2OH2SO3
oxidizing nature:-sulphur dioxide bahves as an oxidizing agent to
wards hydrogen sulphide and carbon monoxide.
2H2S+SO22H2O+3S
reducing nature:-because of its tendencyto remove oxygen in the
pressence of water sulphur dioxide acts as a strong reducing agent.
2FeCl3+SO2+H2OH2SO4+2FeCl2+2H2
Q8) how is sulphuric acid manufacted?
ans)contact process:-now a day sulphuric acid is mostly manufacted by
contact process.
sulphur or iron pyrite is burnt in a regular supply of air to produce
sulphur dioxide.
S+O2SO2
4FeS2+11O2 2Fe2O3+8SO4
the resulting sulphur dioxide along with excess of air is purified
from dust particles and arsenious oxide by passing gases through a
dust chember in to whchsteam is injected.the solid particles of
impurities form droplet of water with steam and settle down.the moist
gases are then dried by passing through a drying tower on which
concentrated sulphuric acid is sprayed.arsenious oxide is then removed
by passing the gases through a chamber provider with shelvespacked
with freshly prepared ferric chloride.
after the removal of dust and other impurities the gases are passed
through a contact chamber packed with plantinished asbestos or
vomaduim pentoxide. the chamber is heated upto 450c where sulphur
dioxide and air combine to form sulphur trioxide.
2SO2+O22SO3
sulphur trioxide thus obtained is absorbed in 97 percent sulphuric
acid flovuing down a tower.the oleum or pyrosulphuric acid thus
produced is diluted in tanks with a calculated amount of water in
order to get 100 percent pure sulphuric acid.
SO3+H2SO4H2S2O2
H2S2O2+H2O2H2SO4
Q9) give laboratory and industrial preparation of chlorine?
ans)laboratory preparation:-chlorine is usually prepared in the
laboratory by the oxidation of hydrochloric acid. concentrated
hydrochloric acid and magnaese dioxide are heated slowly in a round
bottom flask.
on heating greenish yellow chlorine gas comes out which is collected
by the upward displacement of air.it is poisonous gas and hence on
efficient ventilation of the leboratory is necessary.
MnO2+4HClMnCl2+2H2O+Cl2
industrial preparation:-the chlorine gas is obtained on a large scale
by the electrolysis of an aqueous solution of sodium chloride.
chlorine is collected at the anode and sodium hydroxide is produced in
the cell around the cathode.
NaCl+H2OCl2+H2+2NaOH
Q10)what is the action of chlorine on:-
1) CH4 (2) CO (3) NH3
ans)reaction with hydrocarbons:-chlorine reacts with hydrocarbons in
chain reaction to giveCCl4 and HCl
CH4+4Cl2CCl4+4HCl
reaction with carbon monoxide :-chlorine react with carbon monoxide to
give phosgene.
CO+Cl2COCl2
reaction with non metal:-non metal like iron and tin combine with
chlorine on heating.
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