Carbon And Its Compounds Online Test 9th Science Lesson 15 Questions in English

Carbon is one of the most important non-metallic elements. It is a chemical element with the symbol C and atomic number 6.

Antoine Lavoisier named Carbon from the Latin word ‘Carbo’ meaning coal.

Carbon is the main constituent of coal. Coal is a fossil fuel developed from prolonged decomposition of buried plants and animals. So it is clear that all the life forms contain carbon.

The earth atmosphere has only 0.03% of carbon dioxide (i.e.300 parts per million by weight).

The earth’s crust contains only 0.032% of carbon (i.e.320 parts per million by weight) in the form of minerals like carbonates, coal and petroleum. Even though available in small amount in nature, carbon compounds have an immense importance in everyday life.

Carbon is present in our muscles, bones, organs, blood and other components of living matter.

Carbon Chemistry is also called as Living Chemistry. Without carbon there is no possibility for the existence of plants and animals including human.

Carbon has been known since ancient times in the form of soot, charcoal, graphite and diamonds.

In 1772, French scientist Antoine Lavoisier pooled resources with other chemists to buy a diamond, which they placed in a closed glass jar they focused the Sun’s rays on the diamond with a remarkable giant magnifying glass and saw the diamond burn and disappear. Lavoisier noted that the overall weight of the jar was unchanged and that when it burned, the diamond had combined with oxygen to form carbon dioxide. He concluded that diamond and charcoal were made of the same element – carbon.

In 1779, Swedish scientist Carl Scheele showed that graphite also burned to form carbon dioxide.

In 1796, English chemist Smithson Tennant established that diamond is pure carbon and not a compound of carbon and it burned to form only carbon dioxide.

In 1855, English chemist Benjamin Brodie produced pure graphite from carbon, proving graphite is a form of carbon. Although it had been previously attempted without success, in 1955 American scientist Francis Bundy and his co-workers at ‘General Electric’ company finally demonstrated that graphite could be transformed into diamond at high temperature and pressure.

In 1985, Robert Curl, Harry Kroto and Richard Smalley discovered fullerenes, a new form of carbon in which the atoms are arranged in soccer-ball shapes.

Graphene consists of a single layer of carbon atoms arranged in hexagons. Graphene’s discovery was announced in 2004 by Kostya Novoselov and Andre Geim.

Carbon is found both in Free State as well as combined state in nature.

French scientist Antoine Lavoisier, Swedish scientist Carl Scheele, English chemist Smithson Tennant, American scientist Francis Bundy did various experiments on carbon and its compounds.

In the early 19th century, Berzelius classified carbon compounds based on their source.

Organic Carbon Compounds: These are the compounds of carbon obtained from living organisms such as plants and animals. e.g. Ethanol, cellulose, Starch.

Inorganic Carbon Compounds: These are the compounds containing carbon but obtained from non-living matter. e.g. Calcium Carbonate, Carbon Monoxide, Carbon dioxide.

There are millions of organic carbon compounds available in nature and also synthesized manually. Organic carbon compounds contain carbon connected with other elements like hydrogen, oxygen, nitrogen, sulphur etc. Thus, depending on the nature of other elements and the way in which they are connected with carbon, there are various classes of organic carbon compounds such as hydrocarbons, alcohols, aldehydes and ketones, carboxylic acids, amino acids.

As compared to organic compounds the number of inorganic carbon compounds is limited. Among them oxides, carbides, sulphides, cyanides, carbonates and bicarbonates are the major classes of inorganic carbon compounds.

Carbon monoxide (CO) is not a natural component of air. Mainly added to atmosphere due to incomplete combustion of fuels.

Carbon monoxide is the main component of water gas (CO+H2).

Uses of CO2: Fire extinguisher, preservative for fruits, making bread, to manufacture urea, carbonated water, nitrogenous fertilizers, dry ice in refrigerator.

Carbon dioxide occurs in nature as free and combined forms. Combined form is found in minerals like limestone, magnesite. It is formed by complete combustion of carbon or coke.

Uses of CO2: Fire extinguisher, preservative for fruits, making bread, to manufacture urea, carbonated water, nitrogenous fertilizers, dry ice in refrigerator.

Carbon disulphide (CS2) is a Colorless, inflammable, highly poisonous gas.

Uses of Carbon disulphide: Solvent for sulphur, to manufacture rayon, fungicide, insecticide.

Calcium Carbonate (CaCO3) : Prepared by passing Carbon dioxide into the solution of slaked lime.

Sodium bicarbonate (NaHCO3): White crystalline substance, sparingly soluble in water.

Catenation is binding of an element to itself or with other elements through covalent bonds to form open chain or closed chain compounds.

Carbon is the most common element which undergoes catenation and forms long chain compounds. Carbon atom links repeatedly to itself through covalent bond to form linear chain, branched chain or ring structure.

This property of catenations carbon itself is the reason for the presence of large number of organic carbon compounds. So organic chemistry essentially deals with catenated carbon compounds.

Another versatile nature of carbon is its tetravalency. The shell electronic configuration of carbon is 2, 4 (Atomic no: 6). It has four electrons in its outermost orbit.

According to Octet Rule, carbon requires four electrons to attain nearest noble gas (Neon) electronic configuration. So carbon has the tendency to share its four electrons with other atoms to complete its octet. This is called its tetravalency.

40. Which of this bond is used for combining tetravalent carbon with other elements?

The nature of bonding in a compound is the primary factor which determines the physical and chemical characteristics of a compound.

The ability of carbon to form multiple bonds is the main reason for the existence of various classes of carbon compounds.

Alkyne class of compounds has triple bond configuration example is Ethyne.

When one or more hydrogen in hydrocarbons is replaced by other elements like O, N, S, halogens, etc., a variety of compounds having different functional groups is produced.

Isomerism is another special feature of carbon compounds especially found in catenated organic compounds.

The molecular formula of an organic compound represents only the number of different atoms present in that compound. It does not tell about the way in which the atoms are arranged and hence its structure. Without knowing the structure, we can’t name it.

A given molecular formula may lead to more than one arrangement of atoms. Such compounds are having different physical and chemical properties. This phenomenon in which the same molecular formula may exhibit different structural arrangement is called isomerism.

Compounds that have the same molecular formula but different structural formula are called isomers (Greek, isos = equal, meros = parts).

Allotropy is a property by which an element can exist in more than one form that is physically different and chemically similar.

The different forms of that element are called its allotropes. The main reason for the existence of allotropes of an element is its method of formation or preparation.

Diamond: In diamond, each carbon atom shares its four valence electrons with four other carbon atoms forming four covalent bonds. Here the atoms are arranged in repeated tetrahedral fashion which leads to a three dimensional structure accounting for its hardness and rigidity.

Graphite: In graphite, each carbon atom is bonded to three other carbon atoms through covalent bonds in the same plane. This arrangement forms hexagonal layers which are held together one over other by weak Vander Waals forces. Since the layers are held by weak forces graphite is softer than diamond.

Fullerene: The third crystalline allotrope of carbon is fullerene. The best known fullerene is Buckminster fullerene, which consists of 60 carbon atoms joined together in a series of 5- and 6- membered to form spherical molecule resembling a soccer ball. So its formula is C60.

The best known fullerene is Buckminster fullerene, which consists of 60 carbon atoms joined together in a series of 5- and 6- membered to form spherical molecule resembling a soccer ball.

The allotrope was named as Buckminster fullerene after the American architect Buckminster fuller. Because its structure reminded the framework of dome shaped halls designed by Fuller for large international exhibitions, it is called by the pet name Bucky Ball.

A large family of fullerenes exists, starting at C20 and reaching up to C540.

Graphene is most recently produced allotrope of carbon which consists of honeycomb shaped hexagonal ring repeatedly arranged in a plane.

Graphene is the thinnest compound known to man at one atom thick. It is the lightest material known (with 1 square metres weighing around 0.77 milligrams) and the strongest compound discovered (100-300 times stronger than steel). It is a best conductor of heat at room temperature.

Layers of graphene are stacked on top of each other to form graphite, with an inter planar spacing of 0.335 nanometers. The separate layers of graphene in graphite are held together by Vander Waals forces.

In amorphous form of carbon, carbon atoms are arranged in random manner. These forms of carbon are obtained when wood is heated in the absence of air. E.g., charcoal

Carbon is a non-metal found in various allotropic forms from soft powder to hard solid.

All the allotropic forms of carbon are solids whereas its compounds exist in solid, liquid and gaseous state.

Amorphous forms of carbon and graphite are almost black in color and opaque. Diamond is transparent and shiny.

Carbon amorphous forms have low melting and boiling point compared to crystalline forms.

Carbon is insoluble in water and other common solvents. But some of its compounds are soluble in water and other solvents. e.g., Ethanol, CO2 are soluble in water.

Elemental carbon undergoes no reaction at room temperature and limited number of reactions at elevated temperatures. But its compounds undergo large number of reactions even at room temperature.

Oxidation – (Reaction with oxygen) Carbon combines with oxygen to form its oxides like carbon monoxide (CO) and carbon dioxide (CO2) with evolution of heat.

Organic carbon compounds like hydrocarbon also undergo oxidation to form oxides and steam with evolution of heat and flame. This is otherwise called combustion.
2C(s) + O2(g) → 2CO(g)+ heat
C(s) + O2(g) → CO2(g) + heat
CH4(g) + 2O2(g) → CO2(g)+ 2H2O(g) + heat

Carbon reacts with steam to form carbon monoxide and hydrogen. C(s) + H2O(g) → CO(g) + H2(g)

The mixture of carbon monoxide and hydrogen is called water gas.

With sulphur, carbon forms its disulphide at high temperature.
C(s) + 2S(g) → CS2(g)

At elevated temperatures carbon reacts with some metals like iron, tungsten, titanium to form their carbides. Tungsten + Carbon → Tungsten carbide

Even though carbon and its compounds are vital for modern life, some of its compounds like CO, cyanide and certain types of plastics are harmful to humans.

Plastics are a major class of catenated organic carbon compounds. They are made from long chain organic compounds called ‘polymer resins’ with chemical additives that give them different properties.

Drawbacks of plastics: Plastics take a very long time to fully break down in nature. The microbes that break down plastic are too few in nature to deal with the quantity of plastics we produce.

A lot of plastic does not get recycled and ends up polluting the environment. Some types of plastics contain harmful chemical additives that are not good for human health. Burning of plastics releases toxic gases that are harmful to our health and contribute to climate change. One-time use and throwaway plastics end up littering and polluting the environment.

In order to know which plastics are harmful, you will need to learn the secret ‘language’ of plastics (resin codes).The resin code represents the type of polymer used to make the plastic.

The resin codes of plastics were designed in 1988 and are a uniform way of classifying the different types of plastic which help recyclers in the sorting process.

The secret resin codes are shown as three chasing arrows in a triangle. There is a number in the middle or letters under the triangle (an acronym of that plastic type). This is usually difficult to find. It can be found on the label or bottom of a plastic item. The resin codes look very similar to the recycling symbol, but this does not mean that all plastics with a code can be recycled.

The resin codes are numbered from 1 to 7. Resin codes #1 to #6 each identify a certain type of plastic that is often used in products. Resin code #7 is a category which is used for every other plastic (since 1988) that does not fit into the categories #1 to #6.

Plastics in our everyday life can be harmful for two reasons. The first reason is that some types of plastic contain chemicals that are harmful to our health. The second reason is that a lot of plastics are designed to be used just for one time. This use and throwaway plastic cause’s pollution to our environment.

There are three types of plastic that use toxic and harmful chemicals. These chemicals are added to plastics to give them certain qualities such as flexibility, strength, color and fire or UV resistance. The three unsafe plastics are: PVC (resin code #3), PS (resin code #6 also commonly called Thermocol) and PC/ABS (resin code #7).

PVC – Polyvinyl Chloride plastics: Phthalates (chemical additive) copy our hormones. Burning PVC releases dioxins (one of the most toxic chemicals known to humans).

Heavy metals like cadmium & lead are added to PVC.

PS (Polystyrene plastics) Styrene is a building block of this plastic and may cause cancer.

91. What are the disadvantages of PS plastics?

PC – Polycarbonate plastics: PC plastic contains Bisphenol A (BPA). BPA leaks out of PC products used for food and drinks.

BPA increases or decreases certain hormones and changes the way our bodies work.

Explanation
ABS – Acrylonitrile Butadiene Styrene
• Styrene causes problems for our eyes, skin, digestive system and lungs.
• Brominated Flame Retardants (BFRs) are often added.
• Studies show that toxic chemicals leak from this plastic.

The Government of India is progressively taking various legal initiatives to stop plastic pollution by making some provisions and amendments in the Environment (Protection) Act, 1988.

With reference to this act, Government of Tamil Nadu has taken a step forward to ban the usage of some kind of plastic items (Environment and Forests Department, T.N. G.O. No: 84, dated 25/06/2018).

As per the government order cited above, the Tamil Nadu Government has banned the usage of one-time use and throwaway plastics from 1st January 2019. This excellent legislation is designed to protect Tamil Nadu from plastic pollution.

As per the key aspects of new rules along with science-based facts these items have been banned in Tamil Nadu Plastic carry bags, Plastic plates, Water pouches, Plastic straws and Plastic sheets.

Most of the one-time use plates are made from Polystyrene (resin code # 6) which is harmful to our health.

Carbon disulphide (CS2) is directly prepared from Carbon and Sulphur.