by • 14/07/2011 • 9th class ChemistryComments (1)1257

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 more volatile(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.
2) from water:-oxygen is obtained on large scale by electrolysis of water.


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.
2) reaction with metal:-highly reactive metals such as sodium and potassium react rapidly with oxygen at low temperature.
3)reaction with aluminium:- aluminuim powder burns violently in oxygen.flash bulbs used in photography contain aluminium foil in an atmosphere of oxygen.


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. superoxide have an excess amount of oxygen than normal and superoxides.
4) suboxide:- suboxide have less quantity of 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.
due to the presnce of this extra oxygen ozone ozone is used for disinfecting water supplies and large summings pools the atomic oxygen kills any harmful bacteria present because of this property ozone is used to sterilise air in confined and crowded spacessuch as underground railway 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 extraction of 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) which collect in a pool at the bottom. hot compressed air is blown down the 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.


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.
oxidizing nature:- sulphur dioxide bahves as an oxidizing agent to wards hydrogen sulphide and carbon monoxide.
reducing nature:-because of its tendency to remove oxygen in the pressence of water sulphur dioxide acts as a strong reducing agent.







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.
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 whch steam 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 shelves packed 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.
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.


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 is poisonous gas and hence on efficient ventilation of the leboratory is necessary.
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.

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
reaction with carbon monoxide :- chlorine react with carbon monoxide to give phosgene.
reaction with non metal:-non metal like iron and tin combine with chlorine on heating.

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  1. asrar hussain says:

    physics chemistery bilogy

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