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Carbon and its Compounds Class 10 Notes | Science | Term 2 |

Covalent Bond

A bond that is formed by sharing of valence electron between two atoms such that each of them attains the stable electronic configuration or nearest noble gas configuration. 

Covalency 

It is generally defined as the number of electrons contributed by each atom for sharing. 

Now, Carbon has atomic number 6. Electronic configuration of Carbon : K-2 , L-4

It can either lose or gain 4 electrons in order to achieve noble gas configuration. But its difficult since

  • If it gain four electrons in order to form C4- then it would be difficult for the nucleus with six protons to hold on 10 electrons ,i.e., four extra electrons.
  • If it loose four electrons forming C4+ cation then it would require a very high energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding just two electrons.

Allotropic Form of Carbon

The phenomenon of existence of an element in two or more forms which have variable physical properties but similar chemical properties is referred as allotropy.

The three allotropic forms of carbon are Diamond, Graphite and Fullerenes.

Diamond Graphite Fullerenes
Hardest substance known.

Each carbon atom is bonded to other four other carbon atoms leading to formation of rigid three dimensional structure.

Smooth and Slippery.

Each carbon is bonded to three other carbon in the same plane forming the layers of hexagonal network separated by large distance. 

It is a natural occurring allotrope of carbon and first identified was C-60 with football shape. 

 Versatile Nature of Carbon

Catenation: The property of self linking of carbon atoms through covalent bond in order to form long straight or branched chain and drinks of different size is generally defined as catenation.

Tetravalency of Carbon: The valence shell of carbon is filled by four electrons. Thus it forms covalent bonds, i.e., carbon is tetravalent. 

Tendency to form multiple bonds: Due to small size of carbon it has tendency to form multiple bond by sharing more than one electron pair. 

Hydrocarbons

These are the organic compounds containing only carbon and hydrogen.

Saturated Compound: Compounds of carbon that contain only single bond between the carbon atoms are called saturated compounds. Example: Ethane, Propane , Butane

Unsaturated Compound: Compounds of carbon which contain one or more double or triple bond between the carbon atoms are called unsaturated compounds. Example: Ethene, Propene, Butyne.

Alkanes : 

  • General formula CnH2n+2
  • Saturated hydrocarbons
  • Methane CH4
  • Ethane C2H4

Alkenes : 

  • General formula CnH2n
  • Unsaturated hydrocarbons
  • Ethene C2H4
  • Propene C3H6

Alkynes : 

  • General formula CnH2n-2
  • Unsaturated hydrocarbons
  • Ethyne C2H2
  • Propyne C3H4

Homologous Series

A family of organic compound having the same functional group, similar chemical properties and the adjacent members differ by a CH2 unit or 14 mass unit. 

All the members of homologous series can be represented by a general formula.

  • Alkane- Cn H2n+2
  • Alkene Cn H2n
  • Alkyne Cn H2n-2
  • Halo alkane Cn H2n+1 X
  • Alcohol Cn H2n+1 OH
  • Aldehyde Cn H2n+1 CHO
  • Ketone Cn H2n+1 COCn‘H2n+1
  • Carboxylic Acid Cn H2n+1 COOH

All the members belonging to homologous series have the same functional group.

Similar chemical properties are shown by all the members of the series.

The members of homologous series show gradation in physical properties. 

Nomenclature of Organic Compound

Some rules to name the carbon compounds were decided by International Union of Pure and Applied Chemistry. This was done with the aim of maintaining the uniformity throughout the world. Names given on this basis are popularly known as IUPAC names. The rules of the nomenclature are as stated below: 

  • First determine the number of carbon atoms in carbon compounds. Name the carbon compound as per the number of carbon atoms. 
Chain Length Word Root
C1 Meth-
C2 Eh-
C3 Prop-
C4 But-
C5 Pent-
C6 Hex-
C7 Hept-
C8 Oct-
  • Select the longest continuous chain of carbon atoms. This must include carbon atom of double and triple bond and also the functional group. 
  • Saturation or unsaturation determines the primary suffix. ane for alkane, ene for alkene and yne for alkyne. 
  • Number the chain from one end to the other in such a manner in order to give the lowest number in the following order of preferences: Functional group > Double or triple bond > Prefix
  • The position of prefix and suffixes are indicated with help of arabic numerals. These position and name are separated with hyphen. 
  • If there are more than one substituent then they should be written in alphabetical order.

 

Family of organic compound Functional Group Secondary Suffix
Alcohols —OH -ol
Aldehydes —CHO -al
Ketones >C=O -one
Carboxylic acids —COOH -oic acid
Amines —NH2 -amine

Some examples are given below:

Formula Common Name IUPAC Name
CH3OH Methyl alcohol Methanol
CH3CH2CH2OH n-Propyl alcohol Propan-1-ol
HCHO Formaldehyde Methanal
CH3CHO Acetaldehyde Ethanal
CH3COCH3 Acetone Propan-2-one
HCOOH Formic Acid Methanoic acid
CH3COOH Acetic acid Ethanoic acid
CH3CH2COOH Propionic acid Propanoic acid
CH3CH2CH2CHO n-Butyraldehyde Butanal

Chemical Properties of Ethanol (C2H5OH)

It is a colourless liquid at room temperature. It has very low melting point (156 K) and low boiling point (351 K).

It is highly soluble in water. It is a good organic solvent. It is a neutral substance so it does not have any effect on blue litmus solution and red litmus solution. It is one of the main component of alcoholic drinks. 

It reacts vigorously with sodium metal in order to form sodium ethoxide and and evolve H2 gas.

2C2H5OH + 2Na → 2C2H5ONa + H2 (g)

Ethanol on dehydration in presence of concentrated sulphuric acid at 443 K forms ethene gas. H2SO4 absorbs water molecules from alcohol molecules and act as strong dehydrating agent. 

C2H5OH + Conc. H2SO4 → H2C = CH2 (Ethene) + H2

In presence of alkaline KMnO4, ethanol gets oxidized to ethanoic acid. 

C2H5OH + 2[O] → CH3COOH + H2O

Chemical Properties of Ethanoic Acid (CH3COOH)

It is a colourless liquid and is also known as acetic acid. Its has a melting point of 290 K and boiling point is considered to be 391 K. It turns blue litmus red as it is an acid.  It is sour in taste. 

Ethanoic acid reacts with alcohols in the presence of conc. H2SO4 acid to form sweet smelling compounds called esters. This reaction is known as esterification reaction

CH3COOH (Ethanoic acid) + C2H5OH (Ethanol) → CH3COOC2H5 (Ethyl ethanoate) + H2O

Ethanoic acid reacts with bases to form salt and water. 

CH3COOH (Ethanoic acid) + NaOH → CH3COONa (Sodium ethanoate) + H2O

It reacts with carbonate and hydrogen carbonate compound of metal to form its salt and release CO2 gas. 

2CH3COOH (Ethanoic acid) + Na2CO3 (Sodium Carbonate) → 2CH3COONa (Sodium ethanoate) + H2O + CO2

CH3COOH (Ethanoic acid) + NaHCO3 (Sodium Hydrogen Carbonate) → CH3COONa (Sodium ethanoate) + H2O + CO2

Cleansing Action of Soap

The dirt is attached to the surface of a dirty cloth with a thin film of oil or grease. When a dirty cloth is treated with soap and detergent solution then then known Pola tale of the soap and detergent dissolve in oil or grease while the polar heads are held by the surrounding water. Soap and detergent micelle are formed with only organ easy outline at their centre. Soap and detergent is attracted by both greasy and water. When the surface of cloth is mechanically scrub with a wooden paddle or agitated in washing machine. The loosened oily particle are removed from dirty surface and as a result the cloth is cleaned. 

Questions / Answers

Question 1: Which one of the succeeding is not the property of carbon?

  1. Carbon compounds are considered as good conductor of heat and electricity.
  2. Carbon compounds are poor conductor of heat and electricity.
  3. Most of the carbon compounds are considered as covalent compounds.
  4. Boiling and melting point of carbon compounds are lower than those of ionic compounds. 

Answer: A ( Carbon compounds are good conductor of heat and electricity)

Question 2: Why are most carbon compounds poor conductor of electricity?

Answer: Carbon mainly form covalent compounds in which molecules are present instead of ions. In other words, the bonding present in these compounds does not give rise to any ions. 

Question 3: Select hydrocarbon from the given compounds C3H6 , C5H10, C4H10, C2H4, C6H14

Answer: Those hydrocarbons in which all the carbon atoms are connected by only single bonds are said to be in saturation. Thus C4H10 and C6H14 are saturated hydrocarbons. 

Question 4: Write the molecular formula of alcohol that can be derived from butane.

Answer: Butanol 

Question 5: What do you understand by the term functional group in carbon compounds? Write the structural formula and functional group present in ethanol and ethanoic acid.

Answer: An atom or group of atom that substitutes one or more hydrogen atom from the hydrocarbon chain and determines the chemical properties of an organic compound is known as functional group. 

Compound Structural formula Functional group
Ethanol C2H5OH Alcohol
Ethanoic Acid CH3COOH Carboxylic acid     

Question 6: Give IUPAC Name of the given compound 

Answer: Prefix – Chloro at Carbon number 4

Word root – pent

Primary suffix – ane

Secondary suffix – oic acid

IUPAC Name: 4-Chloropentanoic acid

Question 7: A Carbon compound having the molecular formula C2H6O. It is also used as a constituent of wine. On heating the compound A with alkaline potassium permanganate it gets oxidized to give the another compound B which on treating with blue litmus solution turns blue litmus red.
(a) Identify the compound A and write its chemical formula and chemical name.
(b) Identify the compound B and write its chemical formula and chemical name.
(c) Identify the functional group present in the compounds A and B.
(d) Write the chemical equation of the reaction of the compound A with alkaline potassium permanganate.
(e) Name the type of reaction that is taking place for the formation of compound B from the compound A. 

Answer: (a) Since the compound A is a constituent of wine, it is ethyl alcohol or ethanol. The molecular formula of compound A will be C2H5OH and its chemical name is ethanol. 

(b) Compound A, i.e., Ethanol when treated with alkaline potassium permanganate changes into Ethanoic acid. Thus B is Ethanoic acid with chemical formula as CH3COOH.

(c) The functional group in A is alcoholic group and in compound B is carboxylic acid.

(d) C2H5OH + 2[O] → CH3COOH + H2O

(e) Since when the compound changes from A to B there is an increase in the proportion of oxygen. Therefore, it must be an oxidation reaction. 

Question 8: Compare the catenation ability of carbon and silicon.

Answer: The property of self linking of carbon atoms through covalent bond in order to form long straight or branched chain and drinks of different size is generally defined as catenation. Carbon has the higher ability of catenation than silicon due to its smaller size that leads to the greater strength of C—C bond over Si—Si bond. 

Question: Name the functional group which always occur in the middle of the carbon Chain and those functional groups that always occur as a terminal position of the carbon chain?

Answer: Ketonic group always occur in the middle of the carbon chain whereas Aldehydic and Carboxyl group always occur at the terminal positions. 

Question: Would an individual be able to check whether the water is hard by using a detergent?

Answer: No it won’t be possible to check whether the sample of the water is hard with the help of detergent since detergent forms leather easily even in hard water.

Question: What are the advantages of detergent over soap for washing clothes? State one disadvantage also.

Answer: Detergents can be used even when water is hard on the other hand soaps and not suitable for washing purpose when the water is hard. The cleansing action of detergents is strong as compared to the weak cleansing action of soaps.
The disadvantage of detergents over soap is that some of the detergents are not biodegradable, i.e., they cannot be decomposed by microorganisms resulting in water pollution in lakes and rivers. 

#Carbon and its Compounds Class 10 Notes

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