All About Carbon

• Carbon is a very important element present in every living being.
• Carbon has usage in food, fuels, medicines, clothing, and gemstones.
• In the form of graphite, carbon has wide application in the industry
• Carbon nanotubes play a great role in nanotechnology
• Carbon forms a significant part of the mineral world

Occurrence of Carbon

• Carbon is widely distributed on earth in the free or combined state.

Carbon in the Free State

• Carbon exists in the free state in coal, diamond, and graphite

Coal

• It Is a decomposition product of plants buried millions of years ago due to some natural phenomena
• Plants contain carbon compounds
• The buried remains are slowly converted into carbon

Carbonisation

• The conversion of a carbon compound into carbon

Diamond and Graphite

• Diamond and graphite are crystalline forms of carbon found in nature
• Graphite is more abundant than diamond.

Carbon in the Combined State

• It is widely distributed in the combined state.

Carbon Dioxide

• Air contains about 0.03% carbon dioxide (CO₂)

Carbon in Living Organisms

• All living organisms (plants and animals) have carbon compounds
• Everything humans eat that is derived from plants and animals contains carbon compounds.
• The essential ingredients of food (carbohydrates, proteins, fats and vitamins) are compounds of carbon.

Carbon in Minerals

• All carbonate minerals contain carbon.
• Limestone, calcite, and marble are calcium carbonate (CaCO3)
• Dolomite is a mixed carbonate of magnesium and calcium (MgCO3 CaCO3).

Carbon in Natural Gas and Petroleum

• They contain mainly hydrocarbons, i.e., compounds which have only carbon and hydrogen.
• Natural gas is methane (CH4)
• Petroleum is a mixture of various hydrocarbons containing a large number of carbon atoms.

Organic and Inorganic Carbon Compounds

• Compounds containing carbon are of two types: organic and inorganic.
• All carbon-containing compounds, except carbon monoxide, carbon dioxide, carbonates and hydrogencarbonates, are called organic compounds.
• All noncarbon compounds, along with carbon monoxide, carbon dioxide, carbonates and hydrogencarbonates, are called inorganic compounds.

Crystalline and Amorphous Solids

• Solids are divided into two classes: crystalline or true solids, and amorphous solids or pseudosolids.
• Crystalline solids have definite geometrical forms.
• Examples include rock salt, common salt, alum, and sugar
• Amorphous solids do not have definite geometrical forms.
• Examples include gas carbon, pitch and plastic
• The particles constituting a crystalline solid are arranged in an ordered manner in three dimensions.
• The particles constituting an amorphous solid are not arranged in an ordered manner.
• When crystalline solids are broken or cut with a sharp knife, they produce pieces with sharp edges and plane faces.
• When Amorphous solids are broken or cut with a sharp knife we get pieces with curved faces

Allotropy

• The phenomenon of some elements existing in different forms
• Derived from the Greek words allos (meaning 'other') and tropos (meaning 'form').
• Allotropes are chemically the same but different from each other in structure, atomicity or both.
• Carbon, oxygen, phosphorus and sulphur some common elements showing allotropy.
• Diamond, graphite, and the fullerenes are examples of carbon allotropes
• Dioxygen (O2) and ozone (O3) are allotropes of oxygen.

Allotropes Properties

• The allotropes of an element differ in physical properties.
• The allotropes of chemically same, differ in some chemical properties too.
• Graphite is a good conductor of heat and electricity whereas diamond is not.
• Graphite burns in air to give carbon dioxide at 700°C whereas diamond does so at 900°C.
• Ozone (O3) absorbs UV rays whereas dioxygen (O2) does not.
• Ozone is a much stronger oxidizing agent than dioxygen.

Allotropy of Carbon

• Carbon exists in crystalline as well as amorphous forms.
• Diamond, graphite and the fullerenes are the crystalline forms.
• Charcoals, lampblack, coke and gas carbon are the amorphous forms.
• Amorphous forms of carbon contain extremely small crystals of graphite
• They are also called microcrystalline forms.

Crystalline Forms of Carbon

• In crystalline forms, a carbon atom is bonded to three or four other carbon atoms.
• These atoms are further bonded to other carbon atoms.
• Atoms are arranged in a different manner in different crystalline forms of carbon such as diamond and graphite

Diamond Structure

• Has tetrahedral lattice structure
• The costliest gemstone and hardest natural substance known
• It is so hard it can only be cut by another diamond
• Diamonds are formed at the high temperature and pressure that exists over 100 km below the earth's surface.
• They are brought to the surface along with the carrier rock- kimberlite- by volcanic action.
• Diamonds form only one part in over 15 million (15,000,000) parts of the rock.
• Diamonds are found mainly in Australia, Botswana and South Africa.
• Diamonds are artificially produced by heating graphite at a high temperature (5000°C) and pressure (100,000 atmospheres).
• They are generally colourless; coloured varieties (yellow, brown, red, green, blue, grey or even black) are also found in nature
• Colour in diamonds arises due to metallic impurities.
• Less costly varieties (grey and black) have no use as gemstones but are used for cutting glass and drilling rocks.

Properties of Diamond

• Diamond is the hardest solid known.
• It has a density of 3.51 g/cm².
• A properly cut diamond bends back a great percentage of the light falling on it
• It has a very high refractive index (2.42)
• It has a very high melting point (3930 °C).
• It is a bad conductor of electricity
• When ignited, it burns in air at 900°C and in oxygen at 700°C to give carbon dioxide
• Each carbon atom is bonded to four other carbon atoms
• The central carbon atom is bonded to four carbon atoms placed at the vertices of a tetrahedron
• The other carbon atoms are also tetrahedrally bonded to four carbon atoms each.
• This kind of bonding results in the formation of a giant molecule, in which the carbon atoms are packed closely.
• Diamonds high density and hardness is because the carbon atoms are closely packed.

Graphite

• Graphite is a black, opaque solid, found in large deposits in many countries countries like China, South Korea and India.
• It is artificially prepared by strongly heating coke with silica in an electric furnace.

Properties of Graphite

• It has a density of 2.2 g/cm³.
• Graphite is very soft (unlike diamond).
• Graphite melts at 3700°C.
• It is a good conductor of heat and electricity.
• It burns in air at 700°C to give carbon dioxide.

Graphite Structure

• Graphite contains layers of hexagonal rings of carbon atoms, joined together
• Each carbon atom is shared by three rings.
• These rings occur in different planes, arranged parallel to each other
• Each layer is held by the adjacent layer by weak bonds

Uses of Graphite

• Graphite electrodes are widely used.
• Graphite is used as a solid lubricant for machines that work at high temperatures
• Graphite leaves a mark on paper (used in pencils)
• Graphite is used for making crucibles for casting metals.
• A mixture of graphite and linseed oil is used for painting things made of iron.
• Graphite is used in nuclear reactors.

Fullerenes and Carbon Nanotubes

• Fullerenes and carbon nanotubes Fullerenes and carbon nanotubes are crystalline forms of carbon.
• Nanotubes have played a great role in the development of an all together new technology known as nanotechnology.

Coke

• Coke is obtained when coal is heated strongly in the absence of air
• It is more porous, and therefore, more active than coal.

Gas Carbon

• Gas carbon deposits on the walls of a retort when a hydrocarbon is heated in the absence of air
• Gas carbon is a good conductor of electricity and is, therefore, used as an electrode.

Adsorption

• Adsorption is a physical property that is a surface phenomenon
• A thin layer of a substance is formed on the surface of another substance.
• A substance on the surface of which adsorption takes place is called an adsorbent.
• Adsorption is dependent on surface area
• The larger the surface area of the adsorbent, the greater is the adsorption.

Adsorption by Charcoals

• As charcoals have a large surface area in powder form, they are good adsorbents.
• Uses of charcoals are based on this property.
• Wood charcoal is a good adsorbent of gases
• Wood charcoal is used in gas masks to remove poisonous gases.
• Prepared from coconut shells a more active charcoal suitable for gas mask.
• Bone charcoal (or animal charcoal) is used to remove the brown impurities from unrefined sugar.
• Many water impurities are removed by filtration through charcoal.
• Activated coconut charcoal is used for separating a mixture of noble gases (helium, neon, argon, krypton and xenon).
• The different noble gases are adsorbed by the charcoal at different temperatures.
• Activated charcoal facilitates certain chemical reactions and is, therefore, used as a catalyst.
• Chlorine adsorbed on activated charcoal readily combines with hydrogen in darkness
• The reaction between chlorine and hydrogen in darkness is otherwise extremely slow.

Carbon reactions with oxygen or air

• On being lit, carbon burns in an excess of oxygen or air to form carbon dioxide.
• In an insufficient supply of air, carbon monoxide is formed.
• The heat produced makes carbon a good fuel.

Carbon Reactivity

• Carbon has a great affinity for oxygen, so it combines with the oxygen present in many compounds, and thus acts as a reducing agent.
• When heated with coke or charcoal, metal oxides below aluminum are reduced to the corresponding metals.
• Carbon reduction is of great importance in metallurgy
• When steam is passed over red-hot coke, a mixture of carbon monoxide and hydrogen is formed.
• This mixture is called water gas and is of great industrial importance.

Carbon Dioxide

• Carbon dioxide is present in the air (~0.03%)
• Cities have greater carbon dioxide content than in the countryside
• Plants use carbon dioxide for photosynthesis and give it out during the day.
• Plants and animals give it out during respiration
• It is present in the form of carbonates in minerals like limestone or marble
• Present in dolomite and calamine

Thermal Decomposition of Carbonates

• The thermal decomposition of metal carbonates (except a few like Na2CO3 and K2CO3) gives CO2
• When a carbonate or a hydrogencarbonate is treated with an acid, CO₂ is evolved with effervescence

Fermentation of a Sugar

• CO2 is evolved during the fermentation of a sugar (with yeast)

Production of Ethanol & Alcohol

• CO2 is produced during ethanol production by the molasses obtained from the sugar industry.

Laboratory Preparation of Carbon Dioxide

• In the lab, carbon dioxide is prepared by the action of dilute hydrochloric acid on marble (CaCO3) chips.
• Carbon dioxide gas heavier than air (~1.6 times)
• It is collected by the upward displacement of air.
• marble chips are placed in a conical flask and covered by water
• The flask is fitted with a thistle funnel and a delivery tube bent at 90
• Dilute HCl is poured through the thistle funnel into the flask
• A brisk reaction takes place and the delivery tube first and then collects in the gas jar by displacing the air upwards.

Properties Of Carbon Dioxide

• Colourless gas lighter than air
• Under 1 atmosphere pressure, the carbon dioxide gas directly solidifies -78.5°C.
• The solid is called dry ice and sublimes at this temperature
• Under ordinary conditions, water dissolves its own volume of the gas.
• Under high pressures, the gas is highly soluble in water, the property used in making soda water or a fizzy drink.
• Dissolved CO₂ bubbles out vigorously when the pressure is released.
• As carbon dioxide is incombustible, its used as fire suppressant.
• Also used as a fire suppressant due to its heavier composition than air.
• An active metal abstracts oxygen from CO2 (setting C free) when burnt in the gas.
• White smoky scales of magnesium oxide (MgO) are deposited on the inner walls of the jar.

Properties of Carbon Dioxide

• The aqueous solution of CO₂ is weakly acidic and turns blue litmus wine-red.
• The aqueous solution of CO2 contains carbonic acid.
• Metal oxides are basic natured and Reacts with metal oxides to form the metal carbonates, which are salts

Reaction with Limewater

• Limewater is a dilute solution of calcium hydroxide.
• Clear limewater turns milky when CO2 is passed through it.
• Milkiness disappears when an excess of CO2 is passed through the liquid.
• The milkiness reappears when the above solution is boiled.

Carbon Dioxide and the Environment

• Essential for life in low concentrations in the air, the environment in high concentrations

The Greenhouse Effect

• A greenhouse is actually a glasshouse inside which we can grow plants.
• The carbon dioxide traps the heat of the sunrays and keeps radiating it back so that the warmth of the earth is retained.
• A gas that traps heat in the environment and keeps the surroundings warm is a greenhouse gas
• Thus, CO₂ is a greenhouse gas and other such gases in our environment are mainly methane fluocarbons (emitted by cattle dung) (used as coolants in fridges and air conditioners).

How to reduce Global Warming or the Greenhouse effect

• Afforestation by using up the increased - CO, in photosynthesis.
• Avoid deforestatisation and industrialisation.

Action on natural water

• Natural water is slightly acidic to slightly alkaline (pH 6.5-8.5)
• So, the gas tends to bring down the pH of that is open to the atmosphere.
• Marine organisms thrive better in alkaline water than in acidic water
• The increasing proportion of dissolved CO₂ is lowering the pH of sea water causing a threat to marine life

Uses of Carbon Dioxide

• Used in the industry for the manufacture of (i) metal carbonates and hydrogen-carbonates, e.g., soda ash (Na2CO3), washing soda (Na2CO3.10H2O), potassium carbonate (K2CO3) and baking soda, i.e., sodium hydrogencarbonate (NaHCO3), (ii) urea, CO(NH2)2; and (iii) ethanol, C2H5OH.
• It is used in fire extinguishers
• It is extensively used for making soda water and fizzy drinks.
• As a coolant due to it in state od dry ice.
• Used in welding, CO₂ is used in order to prevent the oxidation of the metal by gas.

How to control Fire

• By controlling the supply of air or control combustion of burning material by breaking chain reaction
• Use of water to cool the burners.
• Use of suffocating agent that will blanket the fire and cut off the supply of air
• Action or working principle is that Carbon dioxide, being heavier than air, surrounds the burning object and cuts off the supply of air.
• Put out sodium or sand on fire.
• By breaking the chain reaction by interfering with the production of flame radicals.

Carbon Monoxide: a pollutant and industrial substance

• Carbon monoxide (CO) is a common product of the combustion of carbon-based fuels
• So we will look into both these aspects of the gas here.

Carbon Monoxide Poisoning

• How does the gas affects and how to get rid of its effects.
• The concentration of a substance in ppm

CO Poisoning: Concentration

• The concentration of CO in air is also expressed in ppm.
• The CO level in cities generally varies from 5 to 100 ppm.
• Blood transports oxygen in the body and converts it into oxyhaemoglobin
• CO displaces oxygen from oxyhaemoglobin to form carboxyhaemoglobin
• cuts off oxygen supply to cells, and adverse effects are seen
• Inhaling air with a high CO level may be fatal.
• One should not sleep in a closed room heated by a coal fire.
• Carboxyhaemoglobin slowly loses CO on being exposed to an excess of oxygen, and oxyhaemoglobin is again formed
• A person suffering from CO poisoning should be kept on oxygen
• Important uses include as reducing agent in metallurgy due to its oxygen reduction capabilities
• Iron/bauxite can be reduced by CO in a blast furnace to give iron

Fuels

• A substance that is burnt with a view to obtaining heat or light
• Fuels include wood, cow-dung cakes, coal, petrol, diesel, kerosene, CNG and LPG.
• The calorific value of hydrogen is the highest and those of common fuels, much lower

Calorific Value of a Fuel

• The amount of heat given out by 1 g of a fuel in air or oxygen is known the calorific value
• Expressed in kJ/g
• Of the C-based fuels, CNG is mainly methane (CH4) and LPG, mainly butane (C4H10).
• Used for producing petrol, gas, diesel etc
• A good quality coal contains about 90%
• Used as cleaner fuels
• Cleaner fuels includes wood, cow, dund cake and coal for cooking and petrol with diesel