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CHAPTER VII – Non MetalsScience – IX

Module Objectives

• Recap – How elements are classified and arranged into periodic tables.

• Non-metals examples

• List out the physical properties of non-metals

• Write the chemical properties of non-metals

• Distinguish between metals and non-metals

• Study of two important non-metals – 1. Phosphorous 2. Sulphur, which are used widely.

Phosphorous

• Essential nutrient and components of bones, teeth, gums and blood of animal body.

• Necessary for the growth of the plant and to carry out photosynthesis in plants

• It is the second element of 15th group in periodic table

• SYMBOL – P

• ATOMIC NO. – 15

• MASS NO. – 31

• Electronic Configuration – 1s2,2s2,2P6, 3S2,3P3

Phosphorous - Occurrence

• Highly active element

• Does not occur freely in nature

• Widely distributed in nature in phosphate rocks

• It is main component of bone. So, it occurs in bone ash in the form of calcium phosphate

• Important minerals of Phosphorous.• Note – Apatite is also known as Fluorapatite

Phosphorous - Extraction• Extracted by heating bone ash or rock phosphate

• Mixture of finely powdered rock phosphate, sand (silica) and coke are introduced in electric furnace

• An electric arc struck between the electrodes produces high temperature

• Phosphorous pentoxide is formed by the reaction of rock phosphate and sand (silica)

Allotrophic forms of Phosphorous• Like carbon, phosphorous also exhibits allotropy.

• Two allotropic forms are white phosphorous and red phosphorous

• White phosphorous is obtained by rapid cooling of phosphorous vapour.

• Red phosphorous is prepared by heating white phosphorous to about 2500C along with inert gases

Allotrophic forms of Phosphorous contd.

• When white phosphorous is exposed to air at about 300C, it reacts with oxygen and fumes

• But, it does not react with water

• So this highly reactive element is stored under water

• White phosphorous undergoes spontaneous slow oxidation in air

• This oxidation is visible like a greenish glow in the dark. This phenomenon is known as Phosphorescence.

Phosphorous – Chemical propertiesAction with AIR / OXYGEN

• Phosphorous trioxide is formed when phosphorous is burnt in a limited supply of air.

• Phosphorous pentoxide is formed when phosphorous is burnt in excess of air.

Phosphorous – Chemical propertiesAction with Chlorine

• Phosphorous trichloride is formed when the supply of chlorine is limited.

• Phosphorous pentachloride is formed with excess amount of chlorine

Phosphorous – Chemical propertiesAction with Alkalis

• Phosphine is formed when phosphorous is boiled with Sodium hydroxide

• Phosphine is a colorless gas with an unpleasant odour. It is highly poisonous

• Oxides of phosphorous are acidic in nature. They form oxyacids when they disolve in water.

• Important oxyacids are:• Orthophosphoric acid – H3PO4

• Metaphosphoric acid – HPO3

• Pyrophosphoric acid – H4P2O7

Uses of Phosphorous

• Red Phosphorous is used widely in the manufacture of safety matches

• White phosphorous is used in bullets and in incendiary bombs

• It is used to make phosphorous bronze

• Phosphorous is used in rat poison

• It is widely used in the manufacture of phosphate fertilizers

Phosphorous fertilizers

• Essential for the growth of plants

• Needed to carry out photosynthesis and to give high yield

• Plants absorb phosphorous in the form of water soluble compunds

• Leaves turn yellow when they do not get phosphorous in the required quantity

• So, it is necessary to add phosphorous in the form of chemical fertilizer to soil

Preparation of Super Phosphate

• Manufactured by treating the water insoluble phosphate rock with a specific amount of concentrated sulphuric acid

• Mixture of Calcium sulphate and calcium dihydrogen phosphate is obtained. This mixture is called super phosphate

Sulphur

• Element sulphur has been known from ancient times as Brimstone which means Burning Stone

• Brimstone means burning stone.• Sulphur is used in the treatment of skin diseases and as a fumigant since

ancient times.• Symbol – S• Atomic No. – 16• Atomic Mass – 32• Electronic configuration – 1S2, 2S2, 2P6, 3S2, 3P4

• Sulphur is second element of 16th group in the periodic table• Due to its incompletely filled outer orbit (3S2, 3P4) it readily combines with

other elements forming covalent and ionic bonds.

Occurrence of Sulphur

• Sulphur is highly reactive element.

• Occurs in free state and more abundantly as a compound.

• It occurs in free state as vapour in volcanic eruption

• Main Sulphur ores

• Galena – PbS

• Cinnabar – HgS

• Zinc blende – ZnS

• Gypsum – CaSO42H2O

Extraction of Sulphur

• Sulphur is obtained from underground deposits by Frasch process

• Method is based on the relatively low melting point of sulphur (1190C)

• Sulphur deposits occur at a depth of about 230 to 400 metres.

Extraction of Sulphur

• Concentric pipes are sunk from the surface to the sulphur deposits

• Super heated water at 1700 – 1800C is sent through the outer most pipes

• Same time, hot compressed air is forced down through the central pipe

• Hot water melts sulphur

• Foam is produced which it mixes with hot air

• Foam is brought up to the surface by middle pipes by the action air blast

• Sulphur obtained is about 99.5% pure.

Allotropic form of Sulphur

• Exhibits allotropy like carbon and phosphorus

• Allotropes of sulphur are Rhombic sulphur, monoclinic sulphur and plastic sulphur

Rhombic Sulphur• Powdered Sulphur is dissolved in carbon disulphide to make a saturated

solution.

• It is allowed to evaporate slowly

• Yellow crystals of rhombic sulphur are obtained

• Eight atoms are arranged in octahedral shape

• Hence, it is also called as Octahedral sulphur

Monoclinic Sulphur

• Monoclinic Sulphur which is also known as Prismatic Sulphur or beta-Sulphur, is a yellow crystalline solid

• Take sulphur in China dish and melt it slowly at 1250C

• Allow liquid to cool slowly until a crust is formed at the surface

• Break the crust and pour the liquid only

• Observe crystals of needle-shaped monoclinic sulphur sticking to the sides of dish. This is called Prismatic sulphur

• Rhombic sulphur is stable below 950C while monoclinic is stable above 95.50C

• When Rhombic sulphur is heated above 95.50C monoclinic sulphur is formed

Plastic Sulphur

• Melt sulphur in china dish and molten Sulphur is poured in cold water

• Soft rubber like mass is obtained

• Dark-brown elastic solid is called Plastic sulphur

Effects of heat on Sulphur

• When Sulphur is heated above 1150C it melts and a pale-yellow liquid is obtained

• At 1800C the liquid becomes dark brown and viscous and does not flow

• Ring structure is changed into open chain

• High temperature the chain breaks down

• At about 4350C Sulphur boils and its vapour is formed

Physical properties of allotropes of SulphurProperty Rhombic Sulphur Monclinic Sulphur Plastic

Colour Pale Yellow Dark Yellow Brown

Shape Hard, Octahedral Crystal

Brittle, needle shaped crystal

Rubber like amorphous substance

Density 2.06 g/cc 1.96 g/cc 1.92 g/cc

Melting Point 112.80C 1190C ----

Solubility in Carbon disulphide

Soluble Soluble Insoluble

Solubility in water Insoluble Insoluble Insoluble

Stability of structure Stable below 95.50C Stable above 95.50C Unstable

Chemical Properties

• Sulphur burns within limited supply of air with a blue flame to give sulphur dioxide along with small quantity of sulphur trioxide

• Sulphuric acid is formed when sulphur trioxide dissolves in water

Reaction with non-metals

• Sulphur forms sulphides with other non-metals

• When sulphur vapour is passed through red-hot coke, carbon disulphide is formed

C + 2S CS2

• When hydrogen gas is passed through molten sulphur, hydrogen sulphide is formed

H2 + S H2S

• When sulphur reacts with concentrated nitric acid, sulphuric acid is formed

S + 6HNO3 H2SO4 + 6NO2 + 2H2O

Uses of Sulphur

• Sulphur is mainly used for the manufacture of Sulphuric Acid

• It is good disinfectant and used in manufacture of skin ointments

• Vapours of lime and sulphur are used as insecticides

• Sulphur is the main component of gunpowder and explosives

• Used for vulcanising natural rubber

Vulcanisation

• Natural rubber is a polymer of long chain hydrocarbon

• Becomes sticky when heated and brittle when cooled

• Because of its elasticity, it is not possible to give definite shape to rubber

• When sulphur is added in a definite proportion to the natural rubber, it becomes hard and gets all the desirable properties

• It is easy to give it any definite shape

Combustion

• Production and regulation of fire changed the life of ancient man remarkably.

• Early man found that he could keep himself warm with fire, cook food to make it more tasty

• He used fire to extract metals, to make bricks etc.

• Hence, Use of fire has played a vital role in the development of civilisation

• Combustion is a type of chemical change

• Even today, man depends upon combustion to meet his major energy requirements

What is Combustion?

• When substances (mainly fuels) react with oxidizing agents like oxygen, produce energy in the form of heat and light, this process is called Combustion

• Combustion is a type of chemical change in which energy is liberated and new substances are formed

Types of Combustion

• Crackers undergo combustion very quickly liberating enormous amount of energy in the form of light and heat. This is know as explosion

Note the following chemical reactions• Rusting of iron, that is action of moist air with iron to produce iron oxide

• Oxidation of glucose by oxygen in our body.

• Above said reactions are examples of Combustion which take place very slowly

Calorific Value

• Earlier, heat energy was measured in calories.

• Now, heat energy can be converted into mechanical energy

• Hence, heat energy is also expressed in Joules

Fuel k Cal/gram kJ/gram

Wood 4 17

Coal 7.5 to 8.1 25 to 33

Kerosene 12.5 48

Fuel Oil 10.7 45

LPG 14.2 55

Bio-gas 9.5 40

Hydrogen 39.2 150

Carbonic Fuels

• Carbonic fuels are the main sources of energy

• Coal and petroleum are main carbon fuels

Carbonic Fuels - Petroleum• Petroleum is a complex mixture of many saturated hydrocarbons

• These hydrocarbons have carbon atoms ranging from 4 to 50

• Crude oil and natural gas mixture are obtained from the mines

• After separating natural gas the crude oil mixture is subjected to fractional distillation to separate different fractions

Sl. No Carbon Content Use

Petroleum gas C1 – C4 Refinery fuel and domestic fuel

Naphtha C4 – C6 Automobile fuel

Gasoline (Petrol) C5 – C9 Automobile fuel

Kerosene C10 – C15 Jet rocket, Domestic fuel

Diesel C15 – C20 Automobile fuel

Fuel Oil C20 – C25 Boilers in ships

Comparison between Petrol & Diesel

Petrol Diesel

Less smoke is produced while fuel is burnt

More smoke is produced while fuel is burnt

Fuel cost is high Fuel cost is low

Number of carbon atoms ranges from 5 to 9

Number of carbon atoms ranges from 15 to 20

Part of the fuels converted into useful work is less (when efficiency of the engine is same)

Part of fuel converted into useful work is more (when efficiency is same)

Used in low power engine Used in both light and heavy duty engines

Caution

• Petroleum fuels are non-renewable sources of energy

• They were formed over the cours of millions of years in the earth’s crust

• Petroleum is important source of energy

• Technology of utilising alternate economical sources of energy has not yet been developed

Combustion and air pollution

• Atmosphere is the thin blanket of air around the earth

• It sustains life on the earth

• Major components of pure air are nitrogen, oxygen, carbon dioxide, rare gases and traces of water vapour

• Air is polluted when unwanted substances enter into the atmosphere and cause ill effect on Biotic and Aboitic environment

• Air pollution is principally caused by gases produced combusion

Effect of air pollution on Biotic and Abiotic environment• Carbon dioxide

• Even though carbon dioxide is an essential component of air, if the percentage of the gas increases above a certain limit, it causes pollution.

• When the percentage of carbon dioxide increases, it checks the heat radiations produced by Earth which results in increase of global temperature

• Carbon monoxide• Produced by the partial combustion of carbon fuel• On inhaling air containing carbon monoxide, it combines with hemoglobin of red blood

corpuscles forming carbon-hemoglobin. Then it reduces the oxygen carrying capacity of blood

• Hydrocarbons• 55% of the hydrocarbons present in the atmosphere are formed due to incomplete

combustion of petroleum fuels• Responsible for the smog formation in atmosphere

What is Acid Rain?• Oxides of Nitrogen and Sulphur

• Oxides of nitrogen and sulphur are produced by the combustion of petroleum products and coal which cause Acid Rain

• Oxides of sulphur and nitrogen combine with the water vapour in the atmosphere to form sulphuric acid and nitric acid

• These acids precipitations dissolve in rain water known as Acid Rain

• Acid rain causes extensive damage to stone buildings and sculpture of marbles, limestone, etc

• Stones become pitted and weaken mechanically.

Lead & other pollutants• Lead is added to petrol in the form of tetra ethyle lead for the efficient

working of engines

• It comes out of the engine along with exhaust gases

• Lead causes brain disorder in human beings

Other pollutants• Dust and carbon particles produced due to incomplete combustion and

fly ash are also responsible for air pollution

• They affect the health of living beings

• They spoil the beauty of buildings

References• http://educationalelectronicsusa.com/c/metals-VI.htm• Google Images• http://www.wisegeek.org/

Exercises