NCERT Solutions for Class 10 Science Chapter 2 - Carbon and its Compounds

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Pentane has three structural isomers. These are:

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These are 1. Tetracovalency 2. Catenation.

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Formula of cyclopentane is C₅H₁₀ and its electron dot structure is

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1. Ethanoic acid has the structure:

   

2. Butanone:

   

3. Bromopentane: There are three structural isomers possible for bromopentane:

   

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1. 1-Bromoethane
2. Methanal
3. Hex-1-yne.

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This is because in this reaction oxygen gets added to ethanol.

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A mixture of ethyne and air is not burnt for welding because air also contains nitrogen along with oxygen. Nitrogen burn in oxygen producing oxides of nitrogen such as nitric oxide (NO) and nitrogen dioxide (NO₂) which cause pollution.

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The following two tests are used:

1. Litmus test. Treat the given compound with blue litmus solution. If the blue litmus solution turns red, it is a carboxylic acid and if does not turn red, it is an alcohol.
2. Sodium bicarbonate test. Add some sodium bicarbonate solution to the given compound. If there is a brisk effervescence of a colourless and odourless gas (CO₂) which turns freshly prepared lime water milky, it is carboxylic acid. If there is no effervescence, it is an alcohol.

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The substances which can oxidise other substances by loosing oxygen are called oxidising agents.

Examples are alkaline potassium permanganate solution, acidified potassium dichromate solution etc.

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No, we can’t check whether the water is hard or soft using a detergent. This is because detergent can produce lather even with hard water.

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This is because when soap molecules dissolve in dirt, the dirt is somewhat loosened from the clothes and in order to remove it from clothes, the clothes have to be agitated. For that clothes are beaten on a stone or beaten with a paddle or scrubbed with a brush or the mixture is agitated in washing machines.

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7 covalent bonds

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Ketone

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The fuel is not burning completely.

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The formation of CH₃Cl can be represented as:

Carbon forms single convalent bonds with three H – atoms and one Cl – atom by sharing one electron pair with each C – H bonds are non-polar. But C – Cl bond is polar because C and H leave almost same electronegativity whereas Cl has more electronegativity than carbon.

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A series of compounds having similar structural formulae, same functional group and hence similar chemical properties is called a homologous series. In the homologous series any two adjacent members differ by a CH₂ unit in their molecular formulae.

For example, homologous series of aldehydes (or alkanals) can be represented as:

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Differences between ethanol and ethanoic acid:

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A soap molecule has two ends with different properties. One end is polar i.e. hydrophilic while the other end is non-polar i.e. hydrophobic. The hydrophilic part is water soluble while the hydrophobic part is insoluble in water. When soap is added to water, the hydrophilic end of soap molecules dissolves in water while the hydrophobic end of soap molecules get attracted to each other, which results in the formation of spherical ionic micelles.The hydrophilic end of soap molecule is insoluble in ethanol; thus micelle formation does not occur in ethanol.

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Carbon and its compounds are used as fuels for most applications because they produce a large amount of heat on burning, have low ignition temperature and cobustion is spontaneous.

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When soap is added to hard water, it reacts with the soluble calcium and magnesium salts present in the water to give insoluble calcium salt of soap called scum.

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Soap solution will turn red litmus paper blue because soap is alkaline in nature.

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The addition of hydrogen to unsaturated hydrocarbons in the presence of catalysts like palladium, platinum, or nickel to give saturated hydrocarbons is called hydrogenation.

This reaction is used for hydrogenation of liquid vegetable oils using a nickel catalyst to get artificial or vanaspati ghee.

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C₃H₆ and C₂H₂ are unsaturated hydrocarbons and undergo addition reactions because they contain multiple bonds. An unsaturated hydrocarbon undergoes addition reactions.

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Unsaturated compounds are oxidised by alkaline potassium permanganate with the disappearance of its pink colour; therefore when cooking oil (unsaturated compound) is treated with a few drops of alkaline KMnO₄ solution, the pink colour of KMnO₄ disappears. However with butter, which contains saturated compounds, the pink colour of KMnO₄ does not disappear.

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Soaps are sodium or potassium salts of higher fatty acids e.g., sodium palmitate, C₁₅H₃₅COO^–Na⁺, sodium sterate, C₁₇H₃₅COO–Na+ etc. A molecule of soap consists of two parts:

1. A long chain hydrocarbon part (C₁₅H₃₁ –, C₁₇H₃₅ – etc.) which is soluble in oil and
2. Ionic part on polar group, – COO–Na₊ which is soluble in water. Thus a molecule of soap can be represented as:

The long hydrocarbon chain is insoluble in water but soluble in oil and greases while the ionic or the polar part is soluble in water. Dirty clothes contain greasy and oily substance (dirt). Soap molecules dissociate in water to give carboxylate ion (RCOO_–) and cation (Na₊). When dirty clothes are agitated in soap, the hydrocarbon part of carboxylate group dissolves in greasy or oily dirt particles whereas the polar (COO_–) group remains attached to water. In this way each oil droplet acquires negative charge. These negative charged oil droplets called micelles cannot coalesce and hence form a stable emulsion in water. These small droplets along with dirt can be easily washed away with water. Thus soap helps in removing greasy dirt by producing stable oil in water-type emulsion. Also, soap reduces surface tension of water. Hence, clothes get cleaned.