NCERT Solutions for Class 10 Science Ch 4: Carbon and Its Compounds, is given below.
You will get solutions for;
- In-text questions as well as,
- Exercises questions.
So let’s dive into it!
In-text Questions Set-1
1) What would be the electron dot structure of carbon dioxide which has the formula CO2?
Solution:
2) What would be the electron dot structure of a molecule of Sulphur which is made up of eight atoms of Sulphur? (Hint – The eight atoms of Sulphur are joined together in the form of a ring).
Solution:
In-text Questions Set-2
1) How many structural isomers can you draw for pentane?
Solution:
The structural isomers of pentane are as follows:
n-pentane
2-methylbutane
2, 2-dimethylpropane
2) What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Solution:
Two key properties of carbon that lead to the vast number of carbon compounds are:
– Carbon has four valence electrons, allowing it to form multiple bonds.
– Carbon easily forms covalent bonds with many elements, including oxygen, chlorine, nitrogen, sulfur, and hydrogen.
3) What will be the formula and electron dot structure of cyclopentane?
Solution:
The formula and electron dot structure of cyclopentane is:
4) Draw the structures for the following compounds.
(i) Ethanoic acid
(ii) Bromopentane*
(iii) Butanone
(iv) Hexanal
*Are structural isomers possible for bromopentane?
Solution:
The structures of compounds are given below:
*Yes, the structural isomers of bromopentane are possible.
5) How would you name the following compounds?
Solution:
1. Bromoethane
2. Methanal or Formaldehyde
3. 1 – Hexyne
In-text Questions Set-3
1) Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Solution:
The conversion of ethanol to ethanoic acid is an oxidation reaction. First, ethanol loses a hydrogen molecule to form ethanal, which is oxidation because hydrogen is removed.
Then, oxygen is added to ethanal, forming ethanoic acid. Since adding oxygen is also oxidation, the entire process is an oxidation reaction.
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 used for welding instead of ethyne and air because it produces more heat, which is essential for welding metals. When oxygen and ethyne burn together, they create a very hot blue flame with a higher temperature. In contrast, burning ethyne with air produces a sooty flame with unburnt particles, resulting in less heat.
In-text Questions Set-4
1) How would you distinguish experimentally between an alcohol and a carboxylic acid?
Solution:
When carboxylic acids react with sodium carbonate, they produce carbon dioxide gas, which turns lime water milky. Alcohols do not produce this reaction. This experiment can be used to distinguish between alcohols and carboxylic acids.
The reaction of a carboxylic acid with sodium carbonate is:
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
2) What are oxidizing agents?
Solution:
Oxidizing agents are compounds that either remove hydrogen or add oxygen to another substance. Examples include halogens, potassium nitrate, and nitric acid.
In-text Questions Set-5
1) Would you be able to check if water is hard by using a detergent?
Solution:
You cannot check if water is hard using detergent because detergents are made of ammonium salts or sulphonates of long-chain carboxylic acids. Unlike soaps, they do not react with calcium and magnesium to reveal if the water is hard.
2) People use a variety of methods to wash clothes. Usually, after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
Solution:
Agitation is necessary for clean clothes because it helps soap micelles trap oil, grease, and other impurities. When clothes are agitated, these particles are removed from the fabric and go into the water, leaving the clothes clean.
Exercise Questions
1) Ethane, with the molecular formula C2H6, has
(a) 6 covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds
Solution:
Ethane (C2H6) has 7 covalent bonds.
2) Butanone is a four-carbon compound with the functional group
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol
Solution:
(c) ketone
3) While cooking, if the bottom of the vessel is getting blackened on the outside, it means that
(a) the food is not cooked completely
(b) the fuel is not burning completely
(c) the fuel is wet
(d) the fuel is burning completely
Solution:
(b) the fuel is not burning completely
4) Explain the nature of the covalent bond using the bond formation in CH3Cl.
Solution:
Carbon cannot lose or gain 4 electrons because it requires too much energy, making the system unstable. Therefore, CH3Cl completes its octet by sharing 4 electrons with other atoms, resulting in covalent bonding.
In CH3Cl, carbon needs 4 electrons to complete its octet, each hydrogen needs 1 electron to complete its duplet, and chlorine needs 1 electron to complete its octet. Thus, carbon forms 3 bonds with hydrogen and 1 bond with chlorine by sharing electrons.
5) Draw the electron dot structures for
(a) ethanoic acid
(b) H2S
(c) propanone
(d) F2
Solution:
6) What is a homologous series? Explain with an example.
Solution:
A homologous series is a group of compounds with the same functional group and similar chemical properties. They also share a general formula, but their physical properties change due to increasing molecular size and mass.
For example, methane, ethane, propane, and butane are part of the alkane homologous series, which has the general formula CnH2n+2. Each compound differs by a −CH2 unit from the next one. Here are their formulas:
– Methane: CH4
– Ethane: CH3CH3
– Propane: CH3CH2CH3
– Butane: CH3CH2CH2CH3
7) How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Solution:
| Ethanol | Ethanoic acid |
| Has a good smell | Smells like vinegar |
| It does not react with sodium hydrogen carbonate | Bubbles and fizzes with sodium hydrogen carbonate |
| It has a burning taste | It has sour taste |
| It shows no action on litmus paper | It turns blue litmus paper to red |
8) Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents, such as ethanol also?
Solution:
Micelle formation occurs when dirt and clean water interact. There are two key components: pure water and the dirt (or impurities). Soap also has two parts: an organic tail and an ionic head. The organic tail binds with the dirt, while the ionic head interacts with the water.
As a result, when you rinse the material, the soap molecules lift the dirt away. Soap cleans effectively by forming micelles, which trap dirt and repel water. Other solvents, like ethanol, don’t dissolve the sodium salt of fatty acids, so they can’t form micelles.
9) Why are carbon and its compounds used as fuels for most applications?
Solution:
Carbon and its compounds are commonly used as fuels because they produce a lot of energy. When burned, most carbon compounds release significant amounts of heat and light.
10) Explain the formation of scum when hard water is treated with soap.
Solution:
Scum forms when hard water reacts with soap. The calcium and magnesium in hard water create an insoluble substance called scum.
11) What change will you observe if you test soap with litmus paper (red and blue)?
Solution:
When soap dissolves in water, it forms an alkaline solution because of the presence of NaOH or KOH. This solution turns red litmus paper blue. However, in a soap solution, blue litmus paper stays blue.
12) What is hydrogenation? What is its industrial application?
Solution:
Hydrogenation is a chemical reaction where hydrogen reacts with other compounds, often using catalysts like nickel, palladium, or platinum. This process is mainly used to make organic compounds more saturated.
13) Which of the following hydrocarbons undergo addition reactions: C2H6, C3H8, C3H6, C2H2 and CH4?
Solution:
Unsaturated hydrocarbons, like C3H6 and C2H2, undergo addition reactions.
14) Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.
Solution:
The bromine water test helps to distinguish between unsaturated compounds (like alkenes and alkynes) and saturated compounds. Bromine water is a red-brown solution of bromine in water.
When added to an unsaturated compound, the bromine reacts and the red-brown color disappears. If a compound decolorizes bromine water, it is an unsaturated hydrocarbon (with double or triple bonds). Saturated hydrocarbons (alkanes) do not change the color of bromine water.
15) Explain the mechanism of the cleaning action of soaps.
Solution:
Water contains many impurities and dirt that don’t dissolve. Soap molecules, which are salts like sodium or potassium, have long chains of carboxylic acids. The soap works by having one end of the molecule dissolve in oil (hydrophobic) and the other end dissolve in water (hydrophilic).
When soap is used, the hydrophobic ends bind with the oil and dirt, while the hydrophilic ends stay in the water. This creates structures called micelles that trap the oil and dirt. These micelles form an emulsion with the water, helping to remove impurities from clothes during washing. The hydrophilic end of the soap attracts water, while the hydrophobic end repels it, aligning itself with the oil.