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Q.1) Define the functional group? Give some example of functional groups containing oxygen.
Answer:
A functional group is an atom or group of atoms attached with R that is responsible for the specific properties of an organic compound. In other words, the reactive portion of the molecule, containing other elements(s), is called the functional group. The bonds within the functional groups are usually the site of chemical reactions.
Examples:
| Functional group | General formula | Name of the class | Example | Name of the compound |
|---|---|---|---|---|
| ⎯ OH | R ⎯ OH | Alcohol | CH3 ⎯ OH | Methanol |
| ⎯ CHO | R ⎯ CHO | Aldehyde | CH3 ⎯ CHO | Ethanal |
| ⎯ CO ⎯ | R ⎯ CO ⎯ | Ketone | CH3 ⎯ CO ⎯ CH3 | Propanone |
| ⎯ COOH | R ⎯ COOH | Carboxylic acid | CH3 ⎯ COOH | Ethanoic acid |
Q.2) How can we obtain the organic compounds from natural sources?
Answer:
Natural organic compounds are prepared by living things such as plants and animals. Some organic compounds such as proteins are obtained from animals in the form of meat, mutton, chicken, egg, etc. and fats are obtained in the form of animal fat, milk, butter, etc. Plants are also a rich source of organic compounds. Plants prepare a large number of organic compounds such as carbohydrates, proteins, fats (oil), vitamins, etc. Besides this, when plants and animals are dead, they are buried underneath the earth surface. Under high temperature and pressure, in millions of years of these are converted into fossil fuels. These fossil fuels are the main source of organic compounds.
Read more: KPK G10 Chemistry Notes Chapter-10 (Acids, Bases, Salts)
Chapter 11 – Organic Chemistry
Q.3) What are cycloalkanes?
Answer:
Cycloalkanes are alkanes, in which the carbon atoms are arranged in a ring or cyclic structure. In cycloalkanes, there are no free end carbons (no primary carbons). In the open-chain alkanes, the free end carbon atoms are attached to three hydrogen atoms. Cycloalkanes have two less hydrogen atoms than corresponding straight-chain alkanes. For example, cyclic butane C4H8 has two less hydrogen atoms than non-cyclic butane C4H10.
Q.4) Write down examples of three unsaturated hydrocarbons with structural and condensed formulae.
Answer:
Examples of unsaturated hydrocarbons are as follows:
Q.5) Define hydrocarbons, and briefly discuss their importance?
Answer:
Hydrocarbons are the simplest type of organic compounds, they are composed entirely of carbon and hydrogen atoms. Hydrocarbons are widely used as fuels, like Diesel, Gasoline, Natural gas and Liquefied petroleum gas (LPG) are common examples of hydrocarbons.
Q.6) How alkyl radicals are formed. Discuss it with examples.
Answer:
Alkyl radicals are groups of atoms that are formed when one hydrogen atom is removed from an alkane molecule. When one hydrogen atom is removed from any alkane, it becomes an alkyl radical. The name of the alkyl radical is derived from the name pf the corresponding alkane, in which the last ‘ane’ of alkane is replaced by ‘yl’. An alkyl radical is generally represented by a letter ‘R’.
For example,
| Name of Alkane | CnH2n+2 | Alkyl radical | Name |
|---|---|---|---|
| Methane | -H CH4 ⟶ | CH3 ⎯ | Methyl |
| Ethane | -H C2H6 ⟶ | C2H6 ⎯ | Ethyl |
| Propane | -H C3H8 ⟶ | C3H8 ⎯ | Propyl |
| Butane | -H C4H10 ⟶ | C4H10 ⎯ | Butyl |
Q.7) List some uses of organic compounds.
Answer:
The things we use in our daily life are mostly organic compounds such as the food we eat, the clothes we wear, etc. Our dependence on organic compounds is increasing day by day. It has changed our lifestyle.
i) Uses as food:
The food we eat in our daily life such as milk, meat, egg, vegetables, etc. consists of carbohydrates, proteins, vitamins, fats, etc. which are all organic compounds.
ii) Uses as clothing:
The clothes we wear are made up of fibers. These fibers are either natural such as cotton, silk, wool, etc or synthetic fibers such as nylon, polyester, and acrylic, etc. all these are organic compounds.
iii) Uses as medicine:
Most of the medicines that we use are organic compounds. These are naturally synthesized from plants and are used as medicines. Most of the life-saving drugs such as antibiotics, anti-inflammatory, anti-malarial, etc. are synthesized in the laboratory.
iv) Uses as fuel:
The fuels which we use, such as petrol, diesel oil, compressed natural gas (CNG), coal and natural gas are organic compounds.
v) Uses as chemical materials:
The chemicals that we use such as rubber, paper, ink, plastics, fibers, fertilizers, pesticides, insecticides, cosmetics, paints, detergents, etc. are all organic compounds.
vi) Uses as life molecules:
Thousands of organic molecules are taking part in our body functions. There are four main groups of organic molecules that are carbohydrates, proteins, lipids and nucleic acids that combine to build cells and their parts. These molecules are called life molecules.
Read more: KPK G10 Chemistry Notes Chapter9 (Chemical Equilibrium)
Class 10 Chemistry Notes for kpk textbook
Q.8) Give the general molecular formulae of the following homologous series:
a. alkanes
b. alkenes
c. alkynes
Answer:
a. Alkanes:
CnH2n+2
b. Alkenes:
CnH2n
c. Alkynes:
CnH2n-2
Q.9) Why organic compounds are volatile in nature?
Answer:
Organic compounds are volatile in nature due to the reason that organic compounds are held together by weak intermolecular forces. Their molecules are easily broken and evaporate. Their melting and boiling points are also very low.
Q.10) Why are the chemical properties of a homologous series is always same?
Answer:
Homologous series is the series of organic compounds that have similar structural features but differ from adjacent members by a (⎯ CH2 ⎯) group. They have similar chemical properties because they have the same functional group.
Q.5) Define hydrocarbons, and briefly discuss their importance?
Answer:
Hydrocarbons are the simplest type of organic compounds, they are composed entirely of carbon and hydrogen atoms. Hydrocarbons are widely used as fuels, like Diesel, Gasoline, Natural gas and Liquefied petroleum gas (LPG) are common examples of hydrocarbons.
Q.6) How alkyl radicals are formed. Discuss it with examples.
Answer:
Alkyl radicals are groups of atoms that are formed when one hydrogen atom is removed from an alkane molecule. When one hydrogen atom is removed from any alkane, it becomes an alkyl radical. The name of the alkyl radical is derived from the name pf the corresponding alkane, in which the last ‘ane’ of alkane is replaced by ‘yl’. An alkyl radical is generally represented by a letter ‘R’.
For example,
| Name of Alkane | CnH2n+2 | Alkyl radical | Name |
|---|---|---|---|
| Methane | -H CH4 ⟶ | CH3 ⎯ | Methyl |
| Ethane | -H C2H6 ⟶ | C2H6 ⎯ | Ethyl |
| Propane | -H C3H8 ⟶ | C3H8 ⎯ | Propyl |
| Butane | -H C4H10 ⟶ | C4H10 ⎯ | Butyl |
Q.7) List some uses of organic compounds.
Answer:
The things we use in our daily life are mostly organic compounds such as the food we eat, the clothes we wear, etc. Our dependence on organic compounds is increasing day by day. It has changed our lifestyle.
i) Uses as food:
The food we eat in our daily life such as milk, meat, egg, vegetables, etc. consists of carbohydrates, proteins, vitamins, fats, etc. which are all organic compounds.
ii) Uses as clothing:
The clothes we wear are made up of fibers. These fibers are either natural such as cotton, silk, wool, etc or synthetic fibers such as nylon, polyester, and acrylic, etc. all these are organic compounds.
iii) Uses as medicine:
Most of the medicines that we use are organic compounds. These are naturally synthesized from plants and are used as medicines. Most of the life-saving drugs such as antibiotics, anti-inflammatory, anti-malarial, etc. are synthesized in the laboratory.
iv) Uses as fuel:
The fuels which we use, such as petrol, diesel oil, compressed natural gas (CNG), coal and natural gas are organic compounds.
v) Uses as chemical materials:
The chemicals that we use such as rubber, paper, ink, plastics, fibers, fertilizers, pesticides, insecticides, cosmetics, paints, detergents, etc. are all organic compounds.
vi) Uses as life molecules:
Thousands of organic molecules are taking part in our body functions. There are four main groups of organic molecules that are carbohydrates, proteins, lipids and nucleic acids that combine to build cells and their parts. These molecules are called life molecules.
Q.8) Give the general molecular formulae of the following homologous series:
a. alkanes
b. alkenes
c. alkynes
Answer:
a. Alkanes:
CnH2n+2
b. Alkenes:
CnH2n
c. Alkynes:
CnH2n-2
Q.9) Why organic compounds are volatile in nature?
Answer:
Organic compounds are volatile in nature due to the reason that organic compounds are held together by weak intermolecular forces. Their molecules are easily broken and evaporate. Their melting and boiling points are also very low.
Q.10) Why are the chemical properties of a homologous series is always same?
Answer:
Homologous series is the series of organic compounds that have similar structural features but differ from adjacent members by a (⎯ CH2 ⎯) group. They have similar chemical properties because they have the same functional group.
Long Questions Chemistry Class 10 Notes all chapters
Q.1) (a) List the different characteristics of organic compounds.
Answer:
Organic compounds have many common characteristics due to their molecular structure. Some of the important characteristics are given below.
1. Composition: Organic compounds are mainly composed of carbon and hydrogen atoms. Organic compounds may contain oxygen, nitrogen, sulphur, phosphorus and halogens along with carbon and hydrogen atoms.
2. Covalent Nature: Organic compounds are covalently bonded compounds. They are mainly non-polar in nature with few exceptions. They do not ionize in an aqueous solution.
3. Solubility: Organic compounds are mostly non-polar in nature. So, they are soluble in non-polar solvents like ether, benzene, and carbon tetrachloride etc. Mostly these compounds are less or insoluble in water, which is polar.
4. Low Melting and Boiling Points: Organic compounds have generally low melting and boiling points. This is due to the reason that organic compounds are held together by weak intermolecular forces. They can be easily broken down and are volatile in nature. Therefore, their melting and boiling points are low.
5. Thermal Instability: Organic compounds are usually thermally unstable. They decompose into smaller molecules on heating. This property is of great commercial importance e.g. as in the cracking of petroleum.
6. Inflammability: Organic compounds are inflammable. They burn in the presence of air and produce carbon dioxide and water with huge amount of heat. That is why fuels are organic compounds (wood, Coal, Oil, Natural gas) and their comby=ustion produce a large amount of heat.
7. Reactivity: Reactions involving organic compounds are much slower than reactions which involve inorganic substances, that is why organic reaction requires heating, through mixing and the use of proper catalyst to speed up the reaction.
8. Burn with Smoky Flame: When higher molecular organic compounds burn, they produce smoky (soot) flame due to incomplete combustion.
9. Isomerism: Organic compounds show isomerism. Isomerism is the phenomenon in which two or more compounds having the same molecular formula but different structural formula.
10. Non-Ionic Character: They do not furnish ion. They show molecular reactions. Organic compounds have covalent bond between C – C and C – H. The electronegativity difference is very small, so they are non-polar in nature and show non-ionic character.
11. Similarity in Behaviour: Different organic compounds show close relationship with each other due to the presence of same functional groups.
12. Electrical conductivity: They are poor conductor of electricity both in fused state and in solution form due to the presence of non-polar covalent bonds in most of the organic compounds.
Chemistry Online Course / Notes Class 10th Ch#11
Q.1) (b) Which of these is not an unsaturated molecule?
(i) C4H6
(ii) C6H6
(iii) C8H18
(iv) C3H6
Answer:
(i) C4H6
It is the molecular formula of butyne and it has a triple bond which means it is an unsaturated molecule.
(ii) C6H6
Benzene contains three alternative double bonds it is also unsaturated.
(iii) C8H18
Octane is an alkane with all the single bonds in its molecule. So, C8H18 is not unsaturated it is a saturated molecule with all single bonds.
(iv) C3H6
Propene is an alkene with one double bond in it, so it is unsaturated.
Q.1) (c) Define destructive distillation of coal. Name the different types of products obtained by the destructive distillation of coal.
Answer:
Coal is a rich source of organic compounds. These organic compounds are obtained by the process of destructive distillation. When coal is strongly heated in the absence of air, the process is called destructive distillation or carbonization of coal.
During destructive distillation process, the coal is converted into
i. Coal gas
ii. Coke
iii. Coal tar
iv. Ammonical liquor
These products are the sources of other organic compounds.
Q.2) (a) What is catenation?
Answer:
Catenation: Carbon atoms have the ability to covalently bond with other carbon atoms to form straight chains, branched chains, and rings. This self-linking ability of carbon is called catenation.
Q.2) How does catenation contribute to the diversity of organic compound?
Answer:
The diversity and magnitude of organic compounds is due to the uniqueness of carbon’s bonding and its structure. Carbon’s unique bonding properties allow the formation of variety of structures, including chains and rings of many shapes and sizes. Carbon can make bond with many other types of atoms such as hydrogen, nitrogen, oxygen etc. As carbon is an element but still its compounds are in millions due to the property of catenation, its terta-valency and and mode of bonding. As carbon has the ability to covalently bond with other carbon atoms to form straight chains, branched chains and rings.
Q.3) (a) What information about a compound is provided by a structural formula?
Answer:
Structural formula:
A structural formula shows the number and types of atoms present in a molecule and also shows the bonding arrangement of the atoms. In structural formula all the bonds are represented by a single line (⎯), double bonds are represented by double lines(═), and triple bond are represented by three lines (≡) between the bonded atoms.
Q.3) (b) How are structural formulae used in organic chemistry?
Answer:
Structural formula: Structural formula of a compound is the arrangement of different atoms of various elements around the carbon atoms present in a molecule of a compound.
A structural formula shows the number and types of atoms present in a molecule and also shows the bonding arrangement of the atoms. In structural formula all the bonds are represented by a single line (⎯), double bonds are represented by double lines(═), and triple bond are represented by three lines (≡) between the bonded atoms. For example, the structural formulae of propane (C3H8) and butane (C4H10) are:
Q.4) (a) What do the term saturated and unsaturated mean when applied to hydrocarbons?
Answer:
Saturated Hydrocarbons:
Organic compounds in which each carbon atom in the molecule forms four single covalent bonds with other atoms called saturated organic compounds.
Examples of saturated hydrocarbons are Alkanes. Such as Methane (CH4), Ethane (C2H6), and Propane (C3H8), etc.
Unsaturated Hydrocarbons:
Organic compounds in which at least one double or triple covalent bond is present between carbon-carbon are called unsaturated organic compounds. It can be further divided into alkenes and alkynes.
Alkenes: Hydrocarbons that contain at least one double bond between two carbon atoms.
Alkynes: Hydrocarbons with at least one triple bond between two carbon atoms.
Q.4) (b) What other meanings do these terms have in chemistry?
Answer:
Anything in which no more addition is possible is called saturated and the one which has the capacity for addition without substitution is called unsaturated.
For example, when referring to the chemical solutions, a solution having more amount of solute in it and no more solute can be dissolved in this solution, is called a saturated solution. Whereas the one that is dilute as compared to the saturated solution, having less amount of solute in it and has the capacity to dissolve more solute is called an unsaturated solution.
10th Class Chemistry Notes
Q.4) (c) Classify alkanes, alkenes, alkynes, and aromatic hydrocarbons as either saturated or unsaturated.
Answer:
| Saturated Hydrocarbons | Unsaturated Hydrocarbons |
|---|---|
| Alkanes | Alkenes Alkynes Aromatic hydrocarbons |
Q.5) (a) Can you explain the term homologous series?
Answer:
Homologous series is the series of organic compounds that have similar structural features but differ from adjacent members by a (⎯ CH2 ⎯) group. Each member of the homologous series is called homologue. A general molecular formula can be used to determine the formulae of the whole series.
Characteristics of homologous series
i. They have the same general formula.
ii. They have similar chemical properties because they have the same functional group.
iii. Each member differs from the previous one by methylene (⎯ CH2 ⎯) group.
iv. They have similar methods of preparation.
Q.5) (b) How the straight-chain hydrocarbons are named?
Answer:
Straight chain hydrocarbons are named by adding the Prefix “n” before the name of the hydrocarbon. The “n” stands for normal and is used for straight chain organic compounds. For example, n-Propane, n-Butane, n-Pentane etc.
Q.5) (c) Name the straight-chain alkane with the molecular formula C8H18.
Answer:
Alkane: C8H18
Name: Octane (n-octane)
Structure:
