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NCERT Class 10 Science Textbook Chapter 4 With Answer PDF Free Download
Chapter 4: Carbon and its Compounds
In the last Chapter, we came to know many compounds of importance to us. In this chapter, we will study some more interesting compounds and their properties.
Also, we shall be learning about carbon, an element that is of immense significance to us in both its elemental form and in its combined form.
Look at the items that come in the last column of the above table filled by you – your teacher will be able to tell you that most of them are made up of compounds of carbon.
Can you think of a method to test this? What would be the product if a compound containing carbon is burnt? Do you know of any test to confirm this?
Food, clothes, medicines, books, and many of the things that you listed are all based on this versatile element carbon. In addition, all living structures are carbon-based. The amount of carbon present in the earth’s crust and in the atmosphere is quite meager.
The earth’s crust has only 0.02% carbon in the form of minerals (like carbonates, hydrogen carbonates, coal, and petroleum) and the atmosphere has 0.03% of carbon dioxide.
In spite of this small amount of carbon available in nature, the importance of carbon seems to be immense. In this Chapter, we will know about the properties of carbon that make carbon so important to us.
4.1 Bondin In Carbon– The Covalent Bond
In the previous chapter, we studied the properties of ionic compounds. We saw that ionic compounds have high melting and boiling points and conduct electricity in solution or in the molten state.
saw how the nature of bonding in ionic compounds explains these properties. Let us now study the properties of some carbon compounds.
Most carbon compounds are poor conductors of electricity as we have seen in Chapter 2. From the data are given in Table 4.1 on the boiling and melting points of the carbon compounds, we find that these compounds have low melting and boiling points as compared to ionic compounds (Chapter 3).
We can conclude that the forces of attraction between the molecules are not very strong. Since these compounds are largely non-conductors of electricity, we can conclude that the bonding in these compounds does not give rise to any ions.
Versatile Nature Of Carbon
We have seen the formation of covalent bonds by the sharing of electrons in various elements and compounds. We have also seen the structure of a simple carbon compound, methane.
In the beginning of the Chapter, we saw how many things we use contain carbon. In fact, we ourselves are made up of carbon compounds.
The number of carbon compounds whose formulae are known to chemists was recently estimated to be in millions!
This outnumbers by a large margin the compounds formed by all the other elements put together. Why is it that this property is seen in carbon and no other element?
The nature of the covalent bond enables carbon to form a large number of compounds. Two factors noticed in the case of carbon are –
(i) Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules.
This property is called catenation. These compounds may have long chains of carbon,
branched chains of carbon or even carbon atoms arranged in rings.
In addition, carbon atoms may be linked by single, double or triple bonds.
Compounds of carbon, which are linked by only single bonds between the carbon atoms are called saturated compounds.
Compounds of carbon having double or triple bonds between their carbon atoms are called unsaturated compounds.
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NCERT Solutions Class 10 Science Chapter 4 Carbon and its Compounds
2. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Solution: A mixture of oxygen and ethyne is burnt for welding instead of a mixture of ethyne and air because the production of heat is very important for welding metals. When oxygen and ethyne are burnt, it burns completely and produces a higher temperature than air and ethyne. Oxygen and ethyne produce a very hot blue flame but the mixture of air and ethyne gives out a sooty flame which means that there are unburnt particles, resulting in lesser heat.
1. How would you distinguish experimentally between an alcohol and a carboxylic acid?
Solution: On reaction with Sodium Carbonate, Carboxylic acids produce carbon dioxide gas which turns lime water milky whereas alcohols do not give this reaction. This experiment can be used to distinguish alcohol and carboxylic acid.
Reaction of Carboxylic acid with sodium carbonate:
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
2. What are oxidizing agents?
Solution: Oxidising agents are those compounds that either remove Hydrogen or add oxygen to a compound. Ex: halogens, potassium nitrate, and nitric acid.
4. Explain the nature of the covalent bond using the bond formation in CH3Cl
Solution: Carbon can neither lose 4 electrons nor do gain four electrons as these processes make the system unstable due to the requirement of extra energy. Therefore CH3Cl completes its octet configuration by sharing its 4 electrons with carbon atoms or with atoms of other elements. Hence the bonding that exists in CH3Cl is covalent bonding.
Here, carbon requires 4 electrons to complete its octet, while each hydrogen atom requires one electron to complete its duplet. Also, chlorine requires an electron to complete the octet. Therefore, all of these share the electrons and as a result, carbon forms 3 bonds with hydrogen and one with chlorine.
6. What is a homologous series? Explain with an example.
A homologous series is a series of compounds, which has the same functional group. This also contains a similar general formula and chemical properties. Since there is a change in the physical properties, we can say that there would be an increase in molecular size and mass.
For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series. The general formula of this series is CnH2n+2. Methane CH4 Ethane CH3CH3 Propane CH3CH2CH3 Butane CH3CH2CH2CH3. It can be noticed that there is a difference of −CH2 units between each successive compound.
9. Why are carbon and its compounds used as fuels for most applications?
Solution: Carbon and its compounds are used as fuels for most applications for they have high calorific values and give out a lot of energy. Most carbon compounds give a lot of heat and light when burnt in the air.
10. Explain the formation of scum when hard water is treated with soap?
Solution: Scrum is produced from the reaction of hard water with soap. Calcium and magnesium present in the hard water form an insoluble precipitate that sticks as a white which is also called a scrum.
Carbon and its Compounds NCERT Textbook With Solutions PDF Free Download