Carbon and Its Compounds Class 10 Important Questions with Answers – 2022-2023

Important Questions Class 10 Science Chapter 4 – Carbon & Its Compounds

Science has a history of completely transforming the entire world that we live in. Science combines theoretical and practical knowledge, and students need to understand each concept in detail. 

Chapter 4 of Class 10 Science is about carbon and its compounds. In this chapter, students will concentrate on all the properties of carbon & the characteristics of its bond, as well as learn in-depth about some of the important compounds. The covalent bond of carbon is very interesting and is explained in simple language in the chapter notes. Additionally, the physical and chemical properties are discussed in depth as they are very important to understanding the chemical reactions of carbon compounds. This chapter plays an important role in creating strong basic concepts in organic chemistry. It will also support the students in higher studies and even competitive examinations like JEE and NEET.

The chapter discusses some interesting compounds like ethanol and ethanoic acid. The main topics covered here are soaps and detergents, which are relatively less complex when compared to the other topics. 

Extramarks is one of the leading online educational platforms for students from Class 1 to Class 12. Our academic experts understand the importance of frequently solving questions to understand chemistry concepts better. We have collated questions from different sources, including NCERT textbooks, NCERT Exemplars, past year question papers, other reference books, etc. 

The Important Questions Class 10 Science Chapter 4 covers all the vital points for students to get clear-cut insights into all the topics and sub-topics listed in the chapter. Solving questions would help students improve their performance, boost their confidence, and score well in examinations.

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Important Questions Class 10 Science Chapter 4 With Solutions

Extramarks has prepared Class 10 Science Chapter 4 Important Questions to help students get a consolidated question bank from different sources. By solving these questions, students can properly revise the concepts covered in the Hydrogen chapter and other related terms  by utilising this material.

Below is a list of a few questions and their solutions from our question bank of Important Questions in Class 10 Science Chapter 4.

Question 1: Draw the structure for the ethanoic acid molecule, CH3COOH.   

Answer 1: Ethanoic acid (CH3COOH)

Explanation: CH3COOH is ethanoic acid. It contains two carbon atoms and a -COOH carboxylic acid functional group.

Question 2: Soaps are formed by the saponification of

1. Alcohols
2. Simple ester
3. carboxylic acids
4. glycerides

 Answer 2:  The correct option is d. Glycerides

Explanation: We know that soaps are sodium or potassium derivative salts of long-chain fatty acids.

When triglycerides in fat/oil react with aqueous NaOH or KOH, they are changed into soap and glycerol.

It is called the alkaline hydrolysis of esters (C2H5COOCH3)

The chemical reaction is shown below,

C2H5COOCH3 + NaOH → C2H5COONa(soap)  + CH3OH

Since this reaction leads to soap formation, it is called the Saponification process.

Hence option (d) is the correct answer.

Question 3: Which Two Gases Can be Used in the Fountain Experiment?

• Ammonium chloride and hydrogen chloride gas

• Ammonia and hydrogen chloride gas

• Ammonia and chlorine gas

• Ammonia gas and hydrogen gas

Answer 3: The correct option is (b) Ammonia and hydrogen chloride gas

Explanation: Two gases that can be used in the study of fountain experiments are ammonia gas and hydrogen chloride gas. The investigation introduces concepts like solubility and gas laws at the entry-level. It explains the alkalinity or acidity property of gases when litmus is added to the reaction mixture and shows the colour change caused by the gas dissolving in water. Hence, option b is correct.

Question 4:The functional group of butanone is

• Carboxyl

• Ketonic

• Aldehydic

• Alcoholic

Answer 4: The correct option is (b) ketonic

Explanation:  The suffix -one is used for a ketone functional group. Therefore, the active group in butanone is ketone or ketonic.

Question 5. The enzyme which converts starch into maltose is

• Amylase

• Maltase

• Diastase

• Invertase

Answer 5:  The correct option is (a) Amylase

Explanation:  The enzyme that converts starch into maltose is amylase. Maltose is a disaccharide of two glucose units, whereas starch polysaccharide is made up of amylose and amylopectin. Amylase degrades glycosidic bonds.  

Question 6: The number of C−H bonds in ethane C2H6 molecules are

• 4 

• 6 

• 8 

• 10 

Answer 6:The correct option is  (b) 6

Explanation: In general, we know that all of the bonds in alkane molecules are connected by a single bond. That carbon-carbon is combined with a single bond, and carbon-hydrogen is associated with a single bond, as we consider that there is no hydrogen-hydrogen bond in an alkane.

Therefore, in ethane, one carbon-carbon single bond combining two carbons and three hydrogens is attached to one carbon, and the remaining three hydrogens are joined with another carbon. The ethane molecules can also be written as CH3−CH3. One carbon-carbon bond and six carbon-hydrogen bonds are C−H bonds in ethane molecules. Hence, option b. is the correct option.

Question 7: Alcohol can be produced by the hydration of

• Alkenes

• Alkynes

• Alkynes

• Acids

Answer 7: The correct option is  (a) Alkenes

Explanation: Alcohols can be produced by the hydration of alkenes. Hydration means the addition of water. The production of alcohol takes place through the direct hydration of alkenes. The reaction is reversible. 

Question 8: The odour of acetic acid resembles that of

• Rose

• Burning Plastic

• Vinegar

• Kerosene

Answer 8:  The correct option is (c) Vinegar

Explanation: Acetic acid is also known as ethanoic acid. The formula of acetic acid is CH3COOH. Vinegar solution is a dilute solution of acetic acid in water. The odour of acetic acid resembles that of vinegar.

So the odour of ethanoic acid resembles vinegar option (c)is correct. 

Question 9: IUPAC name of the first compound of the homologous series of ketones, is

• Ethanone

• Methanone

• Propanone

• Butanone

Answer 9: The correct answer is (c) Propanone

Explanation: The first member of the homologous series of ketones is acetone, CH3COCH3. Its IUPAC name is propanone. The parent hydrocarbon is propane. The last alphabet, “e”, is replaced with “one” to obtain propanone.

Question 10: Out of butter and groundnut oil unsaturated in nature?

Answer 10: Groundnut oil

Explanation: Butter is saturated, and groundnut oil is unsaturated. Groundnut oil is unsaturated because it contains long organic chains of carbon connected by double and triple bonds.

Question 11: Which class of carbon compounds is dependable for depleting the ozone O3 layer at the maximum level of the atmosphere? 

Answer 11: The depletion of the ozone layer is responsible for using chemicals known as chlorofluorocarbons.

Question 12: While cooking time, if the bottom surface of the vessel is getting blackened on the exterior surface, it means that

 (a) the food is cooked partially.

 b) the fuel is not burning completely.

 (c) the fuel is wet.

 d) the fuel is burning completely.

Answer 12: The correct answer is (b) The fuel is not burning completely.

Explanation: While cooking, when the bottom surface of the vessel is getting blackened on the outer surface, the fuel is not burning completely. Incomplete combustion happens when there is insufficient oxygen, resulting in the formation of carbon monoxide. If the bottom of the vessel is black outside, the fuel is not burning completely. So the correct option (b) is right.

Question 13: Write the common name &  chemical formula of the initial member of the carbon compounds having a functional group – COOH. 

Answer 13: The first member of the carboxylic acid group is: HCOOH – Methanoic acid.

Explanation: The first member of the carbon compounds having a functional group -COOH is methanoic acid, as shown above.

 H-C=OOH

Question 14:  Which substance is added for the denaturation of ethyl alcohol?

Answer 14:  Methyl Alcohol

Explanation: Denatured alcohol, also called methylated spirits, is ethanol with additives that make it poisonous. Methanol is added  to that of the ethanol solvent and because it is toxic. So the correct answer is methanol.

Question 15: Which ions are responsible for making water hard?

Answer 15: Ca2+ and Mg2+

Explanation: Bicarbonates, chloride and sulphates of Ca2+ and Mg2+ are responsible for the hardness of the water.

Question 16:  What are the two main properties of carbon that lead to the large number of carbon compounds we see around us?

Answer 16: Two main properties of carbon that lead to the large number of carbon compounds we observe around us are

A carbon atom has four valence electrons, which is the maximum number of valency.

Covalent bonding forms easily with carbon atoms and numerous other atoms such as Oxygen, Chlorine, Nitrogen, Sulphur, Hydrogen, etc.

Explanation: The two main properties of carbon that lead to the creation of a maximum number of carbon compounds are-

( 1) Catenation- Carbon has the unique ability to create bonds with other carbon atoms, giving rise to large molecules. The carbon-carbon bond is very strong &  stable also.

(2) Tetravalency – Since a carbon compound has a valency of four, it can bond with four different atoms. Carbon’s bonds with other elements are strong, making these compounds exceptionally stable.

Question 17:  Draw the structures for the following compounds.

(i) Ethanoic acid

(ii) Bromopentane

(iii) Butanone

(iv) Hexanal

Answer 17: i) Ethanoic acid(CH3COOH)

1. ii) Bromopentane(CH3CH2CH2CH2CH2Br)

iii) Butanone(CH3COCH2CH3)

1. iv) Hexanal (CH3CH2CH2CH2CH2CHO)

Question 18: A mixture of Oxygen & ethyne is burnt for welding. Why is a variety of ethyne and air not used?

Answer 18: A mixture of oxygen & ethyne is burned for welding instead of a combination of ethyne & air due to heat production, which is very important for welding metals. If oxygen and ethyne are ignited, it burns completely and produces a higher temperature than air and ethyne. Oxygen and ethyne have a very hot flammable blue flame, but the mixture of air & ethyne gives out a sooty flame, meaning that there are unburnt particles, resulting in lesser heat.

Explanation: A mixture of oxygen and ethyne is burned for welding. But a variety of ethyne and air are not used. It is because ethyne undergoes incomplete combustion in the air, giving off a dark flame. Due to complete combustion, ethyne produces a clean flame with a maximum temperature of 3300 K in an oxygen atom.

Question 19: How would you distinguish experimentally between alcohol & a carboxylic acid?

Answer 19: In reaction with Sodium Carbonate, Carboxylic acids develop carbon dioxide gas that turns lime water milky, whereas alcohols do not have this type of chemical reaction. This experiment can be used to distinguish between alcohol and carboxylic acid.

The reaction of Carboxylic acid with sodium carbonate:

2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

Explanation: We can distinguish alcohol and carboxylic acid by interacting with carbonates/hydrogen. The acid interacts with hydrogen carbonate to liberate carbon dioxide, which turns lime water milky.

CH3COOH + NaHCO3 → CH3COONa + H2O + CO2

    Whereas alcohol shows no evolution of gas if reacted with carbonates.

  C2H5OH + NaHCO3 → No reaction

Question 20: What are oxidising agents?

Answer 20: Oxidising agents are those compounds that either replace hydrogen or add Oxygen to a compound. Ex: halogens, potassium nitrate, and nitric acid.

Explanation: The oxidation reaction is the process in which Oxygen is added, or hydrogen is replaced. The substance that combines Oxygen with others is called an oxidising agent. Example: Alkaline Potassium permanganate. Few substances, like alkaline potassium permanganate & acidified potassium dichromate, are capable of combining Oxygen with others. These are called oxidising agents.

Question 21: Would you be capable of checking if the water solution is hard by using a detergent?

Answer 21: It is impossible to check if water is hard using a detergent because all detergents are ammonium or sulphonates salts of long-chain carboxylic acids. Unlike soaps, they do not interact with calcium and magnesium to distinguish the nature of water.

Explanation- Detergents are ammonium or sulphonate salts of long, heavy-chain carboxylic acids. Unlike soap, they do not interact with calcium and magnesium ions in hard water to form scum. They produce a large amount of lather, irrespective of whether the water is hard or soft. It means that detergents can be used in both soft & hard water. So, it cannot be used to check whether the water is hard.

Question 22: People use several methods to wash clothes. Generally, after adding the soap, they ‘beat’ the dresses on a stone, beat them with a paddle, scrub them with a brush, or put the powder agitated in a washing machine. Why is agitation important to get cleanAnswer 22:Agitation is important to get clean clothes as agitation helps soap micelles catch oil, grease, or any other impurities that must be removed. When they are beaten or agitated, the dirt particles are taken out of the clothes’ surfaces and drain into the water, thus cleaning the clothes.

Explanation:  A soap molecule has two parts, namely hydrophobic & hydrophilic. With the support of these, it attaches to the grease or dirt particle and creates a cluster called a micelle. These micelles remain suspended as a colloid. It is essential to agitate clothes to remove these micelles (entrapping the dirt).

Question 23: Explain the behaviour of the covalent bond using the bond formation in methyl chloride CH3Cl.

Answer 23: Carbon can neither lose nor gain four electrons, as these methods make the system unstable because of the requirement for extra energy. Because methyl chloride, CH3Cl, completes its octet configuration by sharing its four electrons with carbon atoms or with different elements, the bonding in CH3Cl is covalent. Here, carbon requires four electrons to complete its octet, while every hydrogen atom needs a single electron to complete its duplet configuration. Even the chlorine atom requires an electron to complete the octet. Therefore, all of these share electrons, and as a result, carbon forms three bonds with hydrogen and one with chlorine.

Explanation: Carbon has four electrons in its outermost shell and needs to gain or lose four electrons to achieve a noble gas configuration. The carbon atom overcomes this problem by sharing its valence electrons with other carbon atoms or with atoms of any other element.

Three of the four electrons are shared with hydrogen atoms, and one is with a chlorine atom. Thus, it has three (C-H) and one (C-Cl) covalent bonds. These bonds developed by the sharing of electrons are called covalent bonds. Carbon, hydrogen, and chlorine attain the nearest noble gas configurations of Neon, Helium, and Argon, respectively.

Question 24: What is a homologous series? Explain with an example.

Answer 24: A homologous series is a compound with the same functional group. It also contains similar general formulas & chemical properties. Hence, there is a change in the physical properties, and there would be an increase in the molecular size & weight.

For example, methane, ethane, propane, butane, pentane, etc., are all part of the homologous alkane series. The common formula of this homologous series is CnH2n+2; examples are methane CH4, Ethane CH3CH3, Propane CH3CH2CH3 and Butane CH3CH2CH2CH3 etc. It can be noted that there is a difference in methylene −CH2 units between every successive compound.

Explanation: A homologous series is a series of carbon compounds with different numbers of carbon atoms but the same functional group. For example, methane, ethane, propane, butane, pentane, etc., are all members of the alkane homologous series. The common formula of this series is CnH2n+2.

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

It can be noted that there is a difference of −CH2  methylene units between each successive compound.

Question 25: How can ethanol and ethanoic acid be differentiated based on their physical and chemical properties?

Answer 25: Ethanol is a liquid solvent at room temperature with a pleasant smell, while ethanoic acid has a vinegar-like smell. The melting point of ethanoic acid or vinegar is 17°C. It is below room temperature, and hence, it freezes during the winter.

Ethanoic acid reacts with metals and hydrogen carbonates to form a salt, water, and carbon dioxide gas, while ethanol does not interact with them.

Metal Carbonates/ Metal Hydrogen carbonates + Carboxylic acid→ Salt + Water + Carbon dioxide

For example,

2CH3COOH + Na2CO3→ 2CH3COONa + H2O + CO2

Metal Carbonates/ Metal Hydrogen Carbonates + Alcohols → No reaction

For example,

CH3CH2OH + Na2CO3→ No reaction

Explanation: 

Question 26: Why is Carbon & its compounds used as fuels for most applications?

Answer 26: Carbon & its compounds are used as fuels for most applications because they have high calorific values and give out a lot of energy. When burned in the air, most carbon compounds give off a lot of heat and light.

Explanation: Carbon compounds have high calorific values because carbon and its compounds are used as fuels for most applications. They give off a lot of heat and light when burned in the air. Saturated hydrocarbons, like methane compounds, burn with a clean flame without any smoke and are thus environmentally friendly.

Question 27: Why does micelle formation occur when soap is added to H2O? Do you observe if other solvents, like ethyl alcohol solvent, develop micelle formation?

Answer 27: Micelle formation occurs due to the dirt particles in normal and clean water. Two mediums are involved: one is pure water, and the other is dirt (also called impurities). The soap also has two forms:

(i) organic tail &

(ii) ionic head

So the organic tail mixes & dissolves with the dirt, whereas the oil, grease, and ionic head dissolve and mix with the water. Hence, when the material to be cleaned is separated from the water, the soap molecules take off the dirt in the water. Therefore, the soap cleans by forming closed structures through the mutual repulsion of the micelles (positively charged heads).

Several solvents, like ethanol, in which sodium or potassium salts of fatty acids do not mix, cannot form such micelles. Explanation: A soap is a sodium or potassium derivative salt of long-chain fatty acids. It has one polar hydrophilic end & one non-polar hydrophobic end group. These molecules have a special orientation inside water in the form of clusters of molecules in which hydrophobic ends are on the inside of the cluster & ionic ends are on the cluster’s surface, thus keeping the hydrocarbon portion out of water. This formation is known as a micelle. Because the oily dirt particles are collected in the centre of the micelle, soap in the form of a micelle can clean.No, micelle formation does not occur in ethanol solvent because the alkyl chain of soap becomes soluble in alcohol.

Question 28: What changes will you notice if you test soap with different litmus papers (red & blue)?

Answer 28: When soap dissolves in water and produces alkaline sodium or potassium hydroxide (NaOH or KOH), the solution is alkaline. The key changes the colour of the red litmus paper to blue, but in the soapy solution, the blue litmus paper remains blue.

Explanation: Because soap is basic, it will turn red and litmus blue. However, it will not affect blue litmus paper.

Question 29: What is hydrogenation? What is its industrial application?

Answer 29: Hydrogenation is a method or a chemical reaction between hydrogen & other compounds. It is commonly done in the presence of catalysts: for example., nickel, palladium, or platinum. Hydrogenation is mainly used to saturate organic compounds.

Explanation: The conversion of an unsaturated hydrocarbon to a saturated hydrocarbon by adding hydrogen in the presence of a nickel catalyst is called hydrogenation. This reaction is commonly used to hydrogenate vegetable oil into vegetable ghee.

Question 30:  Which hydrocarbons undergo additional reactions: C2H6, C3H8, C3H6, C2H2 & CH4?

Answer 30: Unsaturated hydrocarbons undergo additional reactions. C3H6 and C2H2 are unsaturated hydrocarbons that experience additional reactions.

Explanation: Unsaturated hydrocarbons like alkenes and alkynes will undergo additional reactions. As a result, C3H6 (an alkene with -C=C-) and C2H2 (an alkyne with -C=C-) will exhibit additional reactions.

Question 31: Give a test that can be used to differentiate between saturated & unsaturated hydrocarbons.

Answer 31: The bromine water test – is mainly used to differentiate between unsaturated compounds (like alkenes and alkynes) and saturated compounds. For this purpose, bromine is commonly used as bromine water. A bromine solution in water functions as bromine water. Bromine water has a reddish-brown colour due to the presence of bromine in it. If bromine water is added to an unsaturated compound, bromine gets combined with the unsaturated compound, and the red-brown colour of bromine water is discharged. So, suppose an organic compound decolourises bromine water. In that case, it will be an unsaturated hydrocarbon (alkenes and alkynes containing a double or triple bond), but saturated hydrocarbons (alkanes) do not decolourise bromine water. A bromine water test is performed to differentiate between the unsaturated compounds (alkenes and alkynes) and the saturated compounds. Bromine water is added to a red-brown bromine unsaturated hydrocarbon solution. So if there is discolouration, the combination will be an unsaturated hydrocarbon. Explanation: Butter is a saturated compound, & oil is an unsaturated compound. We can understand the chemical test.

Test: If oil is a mix into a test tube containing alkaline potassium permanganate solution KMnO4, the pink colour of the solution disappears. So, cooking oil causes decolourisation of the solution. It does not happen in the case of butter.

Question 32: Explain the mechanism of the cleaning action of soaps.

Answer 32: There are so many impurities and dirt mixed in water, and the dirt does not become soluble in the water. Soap molecules are a merger of salts such as sodium or potassium (Na or K). These molecules are part of a long chain of carboxylic acids. So, the soap starts cleansing and trapping the dirt when the carbon chain is dissolved in oil and the ionic end is dissolved in water. When this occurs, the soap molecules form structures that are known as micelles and are used for capturing the oil droplets. On the other end are the ionic faces. It will then form an emulsion in the water and help dissolve the dirt or impurities when washing clothes. The soap molecules have various properties at different ends. The first end is the hydrophilic end, which is mixed in the water and is attracted to the water. The second is that the hydrophobic end is dissolved in the hydrocarbons and repels water. The hydrophobic tail aligns itself along the surface of the water because it is insoluble in it. Explanation: A soap is a sodium- or potassium-containing (Na or K )salt of long-chain fatty acids. It has one polar hydrophilic end & one non-polar hydrophobic end. If the soap molecule is at the outer surface of the water, the hydrophobic end of the soap, which is not soluble in water, sticks out of the water with the ionic end. When there is no more space for soap molecules on the surface, these molecules generate a special orientation inside water in the form of clusters,s in which hydrophobic ends are on the inside of the cluster & ionic ends are on the cluster’s surface, thus keeping the hydrocarbon portion out of water. This formation is known as a micelle.

Because the oily dirt is gathered in the middle of the micelle, soap in the form of a micelle can be cleaned.

The ionic ends in the micelles remain connected to water. When the stained clothes material is agitated in a soap solution, the oily dirt particles captured by soap micelles get dispersed in water, & the clothes get cleaned.

Question 33: Carbon exists in the atmosphere in the form of

(a) carbon monoxide CO only

(b) carbon monoxide in traces and carbon dioxide

(c) carbon dioxide only

(d) coal

Answer 33: The correct answer is (c) carbon dioxide only

Explanation: The amount of carbon present in the atmosphere is quite small. The atmosphere has 0.03% of carbon dioxide. So, the correct answer is option (c).

Question 34:  Which of the following statements are commonly correct for carbon compounds? These

 are

1. i) good conductors of electricity
2. ii) bad conductors of electricity

iii) having strong forces of attraction between their molecules

1. iv) does not have strong forces of attraction between all their molecules
2. a) i) & iii)
3. b) ii) and (iii)
4. c) i) and (iv)
5. d) ii) and (iv)

Answer 34: The correct answer is (d) (ii) & (iv)

Explanation: The Carbon compounds form covalent bonds; hence, they have a very weak force of attraction. Carbon compounds are poor conductors of electricity. Carbon forms covalently bonded molecules with strong bonds within the molecule, but intermolecular forces of attraction are weak. Since the electrons are shared between atoms & no charged particles are developed, such covalent compounds are commonly poor conductors of electricity. , which is why the correct answer is option (d).

Question 35: A molecule of ammonia (NH3) has

(a) only single bond

(b) only double bond

(c) only triple bond

(d) two double bonds and one single bond

Answer 35: The correct option (a) is right.

Explanation: Three hydrogen atoms share their electrons with a nitrogen atom to form a molecule of ammonia, NH3. It allows nitrogen and hydrogen atoms to achieve the electronic configuration of the nearest inert gas, Neon and Helium. The shared electron pair is said to donate a single covalent bond. Therefore, there are three single covalent bonds in ammonia. So, the correct answer is option (a).

Question 36: Buckminsterfullerene is an allotropic form of

(a) phosphorus

(b) sulphur

(c) carbon

(d) tin

Answer 36: The correct option is (c) Carbon 

Explanation- Diamond, Graphite, Lonsdaleite, C540, C60 (Buckminsterfullerene or buckyball),  C70, Amorphous Carbon, & a single-walled carbon nanotube, or buckytube. Are the allotropes of carbon

Buckminsterfullerene(C60) is an allotropic form of carbon. These Carbon atoms are arranged in the shape of a football. So, the correct answer is option (c).

Question 37: CH3 – CH2 – OH Alkaline KMnO4 + heat → CH3 – COOH

In the above-given reaction, alkaline potassium permanganate KMnO4 acts as-

(a) reducing agents

(b) oxidising agents

(c) catalyst

(d) dehydrating agent

Answer 37: The correct answer is (b) oxidising agent

Explanation- Two Hydrogen atoms are removed by an atom of Oxygen, resulting in the oxidation of ethanol. Here the addition of Oxygen is provided by potassium.

Question 38: Oils reacting with hydrogen in nickel or palladium catalysts form fats. It is an example of

(a) Addition reaction

(b) Substitution reaction

(c) Displacement reaction

(d) Oxidation reaction

Answer 38: The correct answer is (a) Addition reaction

Explanation: Here, hydrogen is added to oil, which is an addition reaction. In the presence of catalysts such as nickel or palladium, unsaturated hydrocarbons combine with hydrogen to form saturated hydrocarbons. This addition reaction is generally used in hydrogenating vegetable oils using nickel or palladium as a catalyst. Vegetable oils commonly have long unsaturated carbon chains, whereas animal fats have saturated carbon chains. So, the correct answer is option (a).

Question 39: In which of the following compounds, —OH is the functional group?

(a) Butanone

(b) Butanol

(c) Butanoic acid

(d) Butanal

Answer 39: The correct answer is (b) Butanol

Explanation: Compounds with -OH functional group will have a suffix -ol in them, so the answer is (b) Butanol. So, C4H9OH is butanol. Therefore, the correct answer is an option (b).

Question 40: The soap molecule has a

(a) hydrophilic head & a hydrophobic tail

(b) hydrophobic head & a hydrophilic tail

(c) hydrophobic head & a hydrophobic tail

(d) hydrophilic head & a hydrophilic tail

Answer 40: The correct answer is (a) a hydrophilic head and a hydrophobic tail

Explanation: Because of the hydrophobic tail, oil, and grease are trapped inside a micelle. The hydrophobic head forms the outer surface of the micelle. Hence, micelle is easily washed by water. The soap molecule has two ends: the hydrophilic head, which interacts with water, and the hydrophobic tail, which interacts with hydrocarbons. So, the correct answer is option (a).

Question 41: Identify the unsaturated compounds from the following

(i) Propane

(ii) Propene

(iii) Propyne

(iv) Chloropropane

(a) (i) and (ii)

(b) (ii) and (iv)

(c) (iii) and (iv)

(d) (ii) and (iii)

Answer 41: The  correct answer is (d), (ii), and (iii)

Explanation: Propene has a double bond, and Propyne has a triple bond. Hence, they are unsaturated compounds. Those compounds in which the valencies of various atoms are fulfilled by single bonds only are known as saturated compounds. Those compounds in which the valencies of different atoms can not be fulfilled by single bonds  are known as unsaturated compounds. Carbon compounds have double or triple bonds between the atoms to satisfy valencies. Propane (C3H8) and chloropropane (C3H7Cl) are saturated compounds, while propene (C3H6) and Propyne (C3H4) are unsaturated compounds. So, the correct answer is option (d). 

Question 42: Chlorine interacts with saturated hydrocarbons at room temperature in the-

(a) absence of sunlight(h⋎)

(b) presence of sunlight

(c) presence of water molecule

(d) presence of HCl hydrochloric acid

Answer 42: The correct answer is (b) the presence of sunlight

Explanation: In the presence of the sun, Chlorine reacts with Hydrocarbons and displaces Hydrogen atoms.

Question 43: In the soap micelles-

(a) Ionic end of soap is on the cluster’s surface, while the carbon chain is on the inside of the cluster surface.

(b) ionic end of soap is in the inside of the cluster, & the carbon chain is out of the cluster.

(c) both the ionic end & carbon chain are on the inside of the cluster

(d) both the ionic end & carbon chain are on the outside of the cluster

Answer 43: The correct answer is (a) option, the ionic end part of the soap is on the surface of the cluster, although the carbon chain is on the interior of the cluster surface.

Question 44: Pentane has the molecular formula C5 H12. It has

(a) Five covalent bonds

(b) 12 covalent bonds

(c) 16 covalent bonds

(d) 17 covalent bonds

Answer 44: The correct answer is (c) 16 covalent bonds.

Question 45: Ethanol reacts with sodium & forms two products. These are

(a) sodium ethanoate & hydrogen

(b) sodium ethanoate & Oxygen

(c) sodium ethoxide & hydrogen

(d) sodium ethoxide & Oxygen

Answer 45: The correct answer is (c) sodium ethoxide and hydrogen

Explanation: When ethanol reacts with sodium, sodium ethoxide and hydrogen gas are produced. So, the correct answer is option (c).

2Na + 2CH3CH2OH → 2CH3CH2ONa + H2

Question 46: Vinegar is a solution of:

(a) 50% – 60% acetic acid in alcohol

(b) 5% – 8% acetic acid in alcohol

(c) 5% – 8% acetic acid in water

(d) 50% – 60% t acetic acid in water

Answer 46: The correct answer is (c) 5%-8% acetic acid in water

Explanation: Vinegar is a 5-8% solution of acetic acid in water. So, the correct answer is an option (c). 

Question 47: Mineral acids are stronger acids than carboxylic acids because-

(i) the mineral acids are completely ionised

(ii) the carboxylic acids are fully ionised

(iii) the mineral acids are partially ionised

(iv) carboxylic acids are partially ionised

(a) (i) & (iv)

(b) (ii) & (iii)

(c) (i) and (ii)

(d) (iii) and (iv)

Answer 47: The correct answer is (a) (i) and (iv)

Explanation: Mineral acids are completely ionised, whereas carboxylic acids are partially ionised. So mineral acids are stronger than carboxylic acids. Mineral acids such as sulphuric acid, hydrochloric acid, etc., are completely ionised. Hence, they are strong acids. Carboxylic acids are partially ionised; they are weak acids. Therefore, the correct answer is an option (a). 

Question 48: Carbon develops four covalent bonds by sharing its valence electrons with four univalent atoms, such as hydrogen. After the formation of four bonds, a carbon attains the electronic configuration of-

(a) helium

(b) neon

(c) argon

(d) krypton

Answer 48:  The correct answer is (b) option Neon

Explanation: After sharing four valence electrons with four univalent atoms. The electronic configuration of carbon becomes 2, 8, the same as Neon’s electronic configuration refer to Important Questions Class 10 Science Chapter 4.

Question 49: Which of the following does not belong to the identical homologous series?

(a) CH4

(b) C2 H6

(c) C3 H8

(d) C4 H8

Answer 49:  The correct answer is (d)  option C4 H8

Explanation: Common formula for C4H8 is CnH2n, and for other options, it is CnH2n+2

Question 50: The name of the compound CH3– CH2– CHO is

(a) Propanal

(b) Propanone

(c) Ethanol

(d) Ethanal

Answer 50: The correct answer is (a) Propanal

Explanation: This compound has three carbon atoms and an aldehyde which adds the suffix al to 3 carbon compounds.

Question 51: The heteroatoms present in CH3-CH2-O-CH2-CH2Cl are-

(i) oxygen atom

(ii) carbon 

(iii) hydrogen

(iv) chlorine

(a) (i) & (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iv)

Answer 51: The correct answer is (d), (i), and (iv)

Explanation: Oxygen and Chlorine are not among the important components of hydrocarbons; hence they are heteroatoms. So the correct option is (d).

Question 52. Which of the following reactions represents the saponification reaction?

(a) CH3COONa + NaOH CH4 + Na2CO3

(b) CH3COOH + C2H5OH CH3COOC2H5 +H2O

(c) 2CH3COOH + 2Na → 2CH3COONa + H2

(d) CH3COOC2H5 + NaOH → CH3COONa + C2H5OH

Answer 52: The correct answer is (d) CH3COOC2H5 + NaOH → CH3COONa + C2H5OH

Explanation: On reacting with sodium hydroxide (NaOH), which is an alkali,  ethyl acetate, which is an ester, is changed to alcohol & sodium acetate (salt of carboxylic acid). This chemical reaction is called saponification because it is used in preparing soap. So, the correct answer is option (d).

Question 53: Why are detergents better cleansing agents than soaps? Explain.

Answer 53:Detergents are better than soaps because detergents are ammonium or sulphonate salts of long-chain carboxylic acids. Charged ends will not allow precipitation with calcium and magnesium in hard water.. Conversely, soaps will form a precipitate with calcium and magnesium ions in the hard water.

Question 54: Name the functional groups present in the following compounds

(a) CH3COCH2 CH2 CH2 CH3

(b) CH3CH2CH2COOH

(c) CH3CH2 CH2 CH2 CHO

(d) CH3CH2OH

Answer 54: 

1. Ketone
2. Carboxylic acid
3. Aldehyde
4. Alcohol

Explanation: a) >CO represents a functional group of the ketone.

1. b) -COOH represents a functional group of carboxylic acid.
2. c) -CHO represents a functional group of aldehydes.
3. d) -OH represents a functional group of alcohol.

Question 55:  Intake of a tiny quantity of methanol can be lethal. Comment.

Answer 55: Methanol converts to methane in the liver & kills all the cells. Methanol also affects the optic nerves & causes blindness. Therefore intake of a small quantity of methanol can be lethal.

Explanation: Even small amounts of methanol can be lethal because methanol is oxidised to methanal in the liver and methanal interacts quickly with cell components. It coagulates the protoplasm in the same way that cooking thickens an egg.

Question 56: (a) What are hydrocarbons? Give examples also.

(b) Give the structural differences between saturated & unsaturated hydrocarbons with two examples each.

 (c) What is a functional group? Give examples of four different functional groups.

Answer 56:

1. Compounds of Carbon & Hydrogen are called Hydrocarbons. Ex: Ethane, Methane
2. All the bonds in saturated Hydrocarbons are single, whereas bonds in unsaturated Hydrocarbons are either double or triple bonds.

Saturated Hydrocarbon Examples are Ethane, Methane

Unsaturated Hydrocarbons examples are Ethyne, Ethene

1. A functional group is a specific combination of atoms that is responsible for the chemical properties of a compound. Students can refer to Important Questions for Class 10 Science Chapter 4 for examples of CHO-aldehyde, OH-hydroxyl, and COOH-carboxylic acid.

Question 57: An organic compound A, on heating with concentrated sulphuric acid H2SO4, forms a compound B which, in addition to one mole of hydrogen in the presence of nickel, includes a compound C. One mole of compound C on combustion creates two moles of carbon dioxide CO2 and 3 moles of water molecule H2O. Identify the compounds A, B & C and write the chemical equations of the reactions involved.

Answer 57: Compound A is Ethanol

Compound A = CH3CH2OH

CH3CH2OH (in the presence of concentrated H2SO4) → CH2-CH2 + H2O

and Compound B is Ethene

Compound B is CH2= CH2

CH2=CH2 (in the presence of nickel)  → C2H6

Compound C is CH3 — CH3

2C2H6+7O2 → 4CO2 + 6H2O

Question 58:  Esters are sweet-smelling substances & are used in making perfumes. Suggest some activity and reaction in preparing an ester with a well-labelled diagram.

Answer 58:In a test tube, take 1ml ethanol & 1 ml glacial acetic acid and mix a few drops of concentrated H2SO4. Warm the test tube for five minutes over a water bath. Transfer the content to a beaker. The sweet smell confirms the formation of Ester.

CH3COOH + CH3CH2OH CH3COOCH2CH3 + H2O

Explanation: Esters are commonly formed by the chemical reaction of acid & alcohol. The following activity can be carried out to prepare an ester-

Take 1 ml ethanol solution and 1 ml glacial acetic acid in a test tube. Sulfuric acid was added to the test tube in the form of drops. Warm this in a water bath for a few minutes ( at least 5 minutes). Pour this into a glass beaker containing 20-50 ml of water & smell the mixture. If it smells sweet, which means an ester has been formed. Esters are sweet-smelling substances used in making perfumes and as flavouring agents; refer to Important Questions Class 10 Science Chapter 4. 

g perfumes and as flavouring agents; refer to Important Questions Class 10 Science Chapter 4. 

Ethanoic acid + ethyl alcohol Ester + Water

Question 59: A compound C (molecular formula, C2H4O2 ) interacts with Na – sodium metal to form a compound R & release a gas which burns with a pop-up sound. Compound C, on treatment with alcohol A in the presence of an acid, develops a sweet-smelling compound S (molecular formula, C3H6O2 ). In addition to sodium hydroxide NaOH to C, it gives R and water. S on treatment with sodium hydroxide NaOH solution gives back R & A. Identify C, R, A, and S and write down the reactions involved.

Answer 59:

1)Compound C is Ethanoic acid[Acetic acid]

It interacts with sodium metal to form a compound called R.

R is Sodium Ethanoate.

2CH3COOH  +2 Na →2CH3COONa + H2

(in the presence of Conc H2SO4)

2) CH3COOH  +C2H5OH → CH3COOC2H5 + H2O

so compound S is Ester or Ethyl ethanoate, and compound A is Ethanol

3)CH3COOC2H5+NaOH →CH3COONa    + C2H5OH.

So compound R is again Sodium Ethanoate.

So compound C is Ethanoic acid

A is Ethanol

S is Ester and R is sodium Ethanoate.

Question 60:  Name the chemical reaction commonly used in converting vegetable oils to fats. Explain the reaction involved in detail.

Answer 60: The addition reaction is involved in converting oils into fats. This process is known as hydrogenation. Here Saturated fats are formed when unsaturated vegetables are converted to saturated fats, which contain saturated carbons.The nickel acts as a catalyst in the hydrogenation process, and the reaction is given below.

R2C=CR2 + Nickel catalyst +H2 R2CH-CHR2

Animal fats generally contain saturated fatty acids, which are unhealthy, while vegetable oils contain unsaturated fatty acids, which are healthy. 

Question 61: Match the reactions in Column (A) with the names in column (B).

Answer 61:

Question 62. Draw the molecular structure of a hexanal molecule, C5H11CHO.  

Answer 62: Hexanal molecule, C5H11CHO:

Explanation: The structure of the hexanal molecule is shown above. Hex means the carbon skeleton contains six carbon atoms. A ‘nal’ means the functional group is an aldehyde. 

Benefits of Solving Important Questions Class 10 Science Chapter 4

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• Students will learn more about all of the balanced chemical equations and chemical reactions topics covered in Chapter 4 of the Class 10 Science syllabus by referring to the detailed step-by-step solutions provided in our solutions.
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