Carbon And Its Compounds

The electron-dot structure of carbon dioxide (CO₂) is:

The electron- dot structurer of Sulphur (S) is:

Three structural isomers are possible for pentane (C₅H₁₂). These are-

The two properties of carbon which lead to the formation of large number of carbon compounds are as follows:

(i) Catenation: It is ability to form bonds with other atoms of carbon.

(ii) Tetravalency: Since carbon has a valency of four, it is capable of bonding with four other atoms.

The molecular formula of cyclopentane is C₅H₁₀.

The electron-dot structure of cyclopentane is:

(i) The structure of ethanoic acid:

(ii) Structure of Bromopentane:

(iii) Structure of butanone:

(iv) Structure of hexanal:

Yes, there are many structural isomers are possible for bromopentane. Among them, the structure of three isomers are given below:

(i) The compound ( ) contains 2 carbon atoms which means the parent hydrocarbon is ethane. It also contains a bromo group attached to one of the carbon atoms. Thus, the nomenclature of the compound is bromoethane.

(ii) The compound () contains 1 carbon atom which means the parent hydrocarbon is methane. It also contains a functional group called aldehyde group which is represented by the adding a suffix 'al' at the end of name of the compound. Now, the name of carbon chain is modified by deleting the last 'e' of methane and adding the suffix 'al'. Thus, the nomenclature of the compound is 'methanal'.

(iii) The compound contains 6 carbon atoms which means the parent hydrocarbon is hexane. It also contains a triple bond in it which is represented by adding a suffix ‘yne’. Now, replacing the ‘ane’ of hexane by ‘yne’, the name of above compound becomes ‘hexyne’.

The addition of oxygen to a substance is called oxidation. The conversion of ethanol to ethanoic acid is as follows:

Since, in this reaction, one oxygen is added to ethanol, hence it is an oxidation reaction.

A mixture of ethyne and air is not used for welding because when ethyne is burnt in air, it gives a sooty flame due to incomplete combustion which is not enough to melt metals for welding.

Take the samples of alcohol and carboxylic acid in different test tubes and add some sodium hydrogen carbonated in both the tubes.

Carboxylic acid reacts with sodium hydrogen carbonate to give brisk effervescence of carbon dioxide gas but alcohol does not react with sodium hydrogen carbonate.

An oxidising agent is one which oxidises other substances by providing oxygen or removing hydrogen. Alkaline potassium permanganate and acidified potassium dichromate can be used as oxidising agents.

For example: Alkaline potassium permanganate or acidified potassium dichromate are oxidising alcohols to acids, that is, adding oxygen to the starting material.

Detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check the hardness of water by using a detergent.

It is necessary to agitate to get clean clothes because the soap micelles which entrap oily dirt on the surface of dirty cloth have to be removed from its surface. When the dirty clothes are agitated in soap solution, the oily dirt particles entrapped by soap micelles get dispersed in water and the clothes get cleaned.

The number of covalent bonds in ethane (C₂H₆) is 7. Ethane is a saturated hydrocarbon in which all the carbon atoms are connected by only single bonds.

Acetone (CH₃CH₂COCH₃) is an organic compound which contains a ketone as functional group.

While cooking, if the bottom of the cooking utensil is getting blackened on the outside, it means that the fuel is not burning completely.

Carbon has four electron in its outermost shell and needs to gain or loss four electrons to attain noble gas configuration. To overcome this, carbon shares each of the four electrons with each of the three hydrogen atoms and one chloride atom. The bond that are formed by sharing electrons are known as covalent bond.

(a) The electron – dot structure for ethanoic acid (CH₃COOH):

(b) The electron-dot structure for hydrogen sulphide (H₂S):

(c) The electron-dot structure for propane (CH₃COCH₃):

(d) The electron-dot structure for fluorine (F₂):

A series of organic compounds in which hydrogen in a carbon chain is replaced by the same functional group, is called homologous series. Any two adjacent homologues differ by (-CH₂) in their molecular formulae.

All the compounds of a homologous series show similar chemical properties.

Example of homologous series: Alkynes.

All the members of homologous series of alkynes have similar structure and similar chemical properties, so they can be grouped together into the homologous series. The general formula of homologous series of alkynes is C_nH_2n-2. Where, n is the number of carbon atoms in alkyne molecule. The members of alkyne homologous series are:

● Ethyne (C₂H₂)-First member of alkyne homologous series.

● Propyne (C₃H₄)-Second member of alkyne homologous series.

● Butyne (C₄H₆)-Third member of alkyne homologous series.

● Pentyne (C₅H₈)-Four member of alkyne homologous series.

● Hexyne (C₆H₁₀)-Five member of alkyne homologous series.

(a) Differences in physical properties :

(i) Ethanol has a pleasant smell whereas ethanoic acid has the smell of vinegar.

(ii) Ethanol has a burning taste whereas ethanoic acid has a sour taste.

(iii)The boiling point of ethanol is low (351 K) whereas that of ethanoic acid is comparatively high (391 K).

(b) Differences in chemical properties :

(i) Ethanol has no action on any litmus paper but ethanoic acid turns blue litmus to red.

(ii) Ethanol has no reaction with sodium hydrogencarbonate but ethanoic acid gives brisk effervescence of carbon dioxide with sodium hydrogencarbonate.

A soap is a sodium or potassium salt of long chain fatty acids. It has one polar end and one non-polar end. Polar end is hydrophilic in nature whereas non-polar end is hydrophobic. When soap is added to water, it forms a colloidal suspension in water in which the soap molecules cluster together to form spherical aggregates called micelles. In a soap micelle, soap molecules are arranged radially with hydrocarbon ends directed towards the center and ionic ends directed outwards.

No, micelle will not be formed in other solvents such as ethanol.

Carbon and its compounds are used as fuels because they give a lot of heat and light when burnt in air.

(i) When carbon is burned in air, it produces carbon dioxide gas and releases a lot of heat :

(ii) When a carbon compound methane is burned in air, it produces carbon dioxide and water vapour, and releases a lot of heat :

Soap does not work properly when hard water is used. Hard water contains salt of calcium and magnesium. When soap is added with hard water, a large amount of soap in water reacts with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum. This makes the cleaning of clothes difficult.

Since soap is basic in nature, it will turn red litmus paper blue. However, blue litmus paper will remain blue when tested with soap solution.

The addition of hydrogen to an unsaturated hydrocarbon in the presence of nickel (or palladium) catalyst to obtain a saturated hydrocarbon is called hydrogenation.

This reaction is commonly used in hydrogenation of vegetable oil into vegetable ghee (solid fat).

Unsaturated hydrocarbons (alkenes and alkynes) will give addition reactions. Being unsaturated hydrocarbons, C₃H₆ (alkene) and C₂H₂(alkyne)will give addition reactions.

Take butter and cooking oil in two separate test tubes and add bromine water in both the tubes. Cooking oil decolourises the bromine water which means it is an unsaturated compound whereas butter does not decolourise the bromine water showing it is a saturated compound.

Soaps are molecules in which the two ends have differing properties, one is hydrophilic, that is, it dissolves in water, while the other end is hydrophobic, that is, it dissolves in hydrocarbons. When soap is at the surface of water, the hydrophobic ‘tail’ of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon ‘tail’ protruding out of water.

Inside water, these molecules have a unique orientation that keeps the hydrocarbon portion out of the water. This is achieved by forming clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle. Soap in the form of a micelle is able to clean, since the oily dirt will be collected in the center of the micelle. The ionic ends in the micelles remain attached to water. When the dirty clothes are agitated in soap solution, the oily dirt particles entrapped by soap micelles get dispersed in water and the clothes get cleaned.