Samacheer Kalvi Class 10 Science Chapter 11 Carbon and its Compounds

I. Choose the best answer:

Question 1. The molecular formula of an open-chain organic compound is C3H6. The class of the compound is
(a) alkane
(b) alkene
(c) alkyne
(d) alcohol
Answer: (b) alkene
In simple words: The formula C3H6 matches the general formula for alkenes, which is CnH2n. This means it is an alkene, a type of hydrocarbon with at least one carbon-carbon double bond.

🎯 Exam Tip: Remember the general formulas for different hydrocarbon series: alkanes \(C_nH_{2n+2}\), alkenes \(C_nH_{2n}\), and alkynes \(C_nH_{2n-2}\) to quickly classify compounds.

Question 2. The IUPAC name of an organic compound is 3-Methyl butan-1-ol. What type of compound it is?
(a) Aldehyde
(b) Carboxylic acid
(c) Ketone
(d) Alcohol
Answer: (d) Alcohol
In simple words: The suffix "-ol" in the name "3-Methyl butan-1-ol" clearly indicates that this compound belongs to the alcohol family. Alcohols contain a hydroxyl (-OH) functional group.

🎯 Exam Tip: Pay close attention to the suffixes in IUPAC names as they reveal the functional group and class of the organic compound.

Question 3. The secondary suffix used in IUPAC nomenclature of an aldehyde is:
(a) -ol
(b) -oic acid
(c) -al
(d) -one
Answer: (c) -al
In simple words: In the naming system for organic chemicals, the part "-al" at the end of a name tells us that the compound is an aldehyde. Aldehydes contain a carbonyl group (\(C=O\)) at the end of a carbon chain.

🎯 Exam Tip: Learn the common secondary suffixes for different functional groups, such as -al for aldehydes, -ol for alcohols, -oic acid for carboxylic acids, and -one for ketones.

Question 4. Two successive members of a homologous series must have a difference of -CH2 in the molecular formula. C3H8 \( \xrightarrow{\text{+CH2}} \) C4H10. The successive members of a homologous series must have a difference of
(a) C3H8 and C4H10
(b) C2H2 and C2H4
(c) CH4 and C3H6
(d) C2H5OH and C4H8OH.
Answer: (a) C3H8 and C4H10
In simple words: For compounds to be in the same homologous series, they must differ by a \(-\text{CH}_2\) unit. C3H8 (propane) and C4H10 (butane) perfectly show this difference, making them successive members of the alkane series.

🎯 Exam Tip: Always check that the molecular formulas of successive members in a homologous series differ by exactly one \(-\text{CH}_2\) group for a correct identification.

Question 5. C2H5OH + 3O2 → 2CO2 + 3H2O is a:
(a) Reduction of ethanol
(b) Combustion of ethanol
(c) Oxidation of ethanoic acid
(d) Oxidation of ethanal
Answer: (b) Combustion of ethanol
In simple words: When ethanol (C2H5OH) reacts with oxygen (3O2) to produce carbon dioxide (2CO2) and water (3H2O), it's a burning process, which is called combustion. This reaction releases energy, often as heat and light.

🎯 Exam Tip: Recognize combustion reactions by the presence of oxygen as a reactant and carbon dioxide and water as products, especially for organic compounds.

Question 6. Rectified spirit is an aqueous solution which contains about ______ of ethanol.
(a) 95.5%
(b) 75.5%
(c) 55.5%
(d) 45.5 %.
Answer: (a) 95.5%
In simple words: Rectified spirit is a mixture mostly made of ethanol, with a small amount of water. It is known to contain 95.5% ethanol and 4.5% water, which is the highest concentration possible through simple distillation.

🎯 Exam Tip: Remember the specific percentage composition of rectified spirit as it is a common fact asked in chemistry exams.

Question 7. Which of the following are used as anaesthetics?
(a) Carboxylic acids
(b) Ethers
(c) Esters
(d) Aldehydes
Answer: (b) Ethers
In simple words: Ethers are a group of organic compounds that were historically used in medicine to make people unconscious during surgery. Their ability to induce a state of insensitivity to pain made them valuable as early anaesthetics.

🎯 Exam Tip: Relate functional groups to their common applications, such as ethers being used as anaesthetics, to help recall their properties.

Question 8. TFM in soaps represents ______ content in soap.
(a) mineral
(b) vitamin
(c) fatty acid
(d) carbohydrate.
Answer: (c) fatty acid
In simple words: TFM stands for Total Fatty Matter, which tells you how much actual cleaning ingredient (fatty acids) is in a bar of soap. A higher TFM usually means better quality soap, indicating a larger proportion of soap-forming oils.

🎯 Exam Tip: Know that TFM is a key quality indicator for soaps, directly reflecting the amount of cleansing fatty matter present.

Question 9. Which of the following statements is wrong about detergents?
(a) It is a sodium salt of long chain fatty acids
(b) It is sodium salts of sulphonic acids
(c) The ionic part in a detergent is \(-\text{SO}_3^-\text{Na}^+\)
(d) It is effective even in hard water.
Answer: (a) It is a sodium salt of long-chain fatty acids
In simple words: Detergents are actually sodium salts of sulphonic acids, not fatty acids. This key difference makes detergents more effective in hard water compared to soaps, which are salts of fatty acids.

🎯 Exam Tip: Differentiate clearly between soaps (fatty acid salts) and detergents (sulphonic acid salts) to answer questions about their composition and behavior in hard water.

II. Fill in the blanks:

Question. Fill in the blanks.
1. An atom or a group of atoms which is responsible for chemical characteristics of an organic compound is called Functional group.
2. The general molecular formula of alkynes is \( \text{C}_\text{n}\text{H}_{2\text{n}-2} \).
3. In IUPAC name, the carbon skeleton of a compound is represented by root word.
4. Unsaturated compounds decolourize bromine water.
5. Dehydration of ethanol by cone. Sulphuric acid forms ethene.
6. 100% pure ethanol is called absolute alcohol.
7. Ethanoic acid turns Blue, red litmus to red.
8. The alkaline hydrolysis of fatty acids is termed as Saponification.
9. Biodegradable detergents are made of straight chain hydrocarbons.
Answer:
1. Functional group
2. \( \text{C}_\text{n}\text{H}_{2\text{n}-2} \)
3. root word
4. unsaturated
5. ethene
6. absolute alcohol
7. Blue, red
8. Saponification
9. straight
In simple words: These blanks cover basic facts about organic chemistry, from naming rules to properties of specific compounds like ethanol and detergents. Functional groups determine how compounds react, and homologous series have predictable formulas.

🎯 Exam Tip: Memorize the definitions of key terms like "functional group," "homologous series," and "saponification," as well as the general formulas for different hydrocarbon classes.

III Match the following:

Question 1. Match the Column I and Column II.

🎯 Exam Tip: For matching questions, quickly identify the most obvious pairs first, then use the process of elimination for the remaining items.

IV. Assertion and Reason:

Question 1. Assertion: Detergents are more effective cleansing agents than soaps in hard water. Reason: Calcium and magnesium salts of detergents are water soluble.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: Detergents clean better in hard water than soaps because the compounds they form with calcium and magnesium (which make water "hard") can dissolve. Soaps, on the other hand, form insoluble "scum" in hard water.

🎯 Exam Tip: Understand the chemistry of hard water and how detergents, unlike soaps, avoid forming insoluble precipitates with calcium and magnesium ions.

Question 2. Assertion: Alkanes are saturated hydrocarbons. Reason: Hydrocarbons consist of covalent bonds.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (d) Assertion and Reason are correct, Reason doesn't explains Assertion.
In simple words: Alkanes are indeed saturated hydrocarbons, meaning they only have single bonds. It is also true that hydrocarbons use covalent bonds. However, the reason about covalent bonds does not directly explain *why* alkanes are saturated.

🎯 Exam Tip: In assertion-reason questions, both statements must be true, and the reason must provide a direct and accurate explanation for the assertion to select option (a).

V. Short answer questions:

Question 1. Name the simplest ketone and give its structural formula.
Answer: The simplest ketone is Propanone.
Its structural formula is: \( \text{CH}_3-\text{CO}-\text{CH}_3 \). Propanone is also commonly known as acetone.
In simple words: The easiest ketone you can find is called propanone, and it has three carbon atoms with a double-bonded oxygen on the middle carbon.

🎯 Exam Tip: Remember that ketones must have at least three carbon atoms, with the carbonyl group (\(C=O\)) bonded to two carbon atoms, making propanone the smallest possible ketone.

Question 2. Classify the following compounds based on the pattern of carbon chain and give their structural formula:
(i) Propane
(ii) Benzene
(iii) Cyclo butane
(iv) Furan.
Answer:

Each compound can be grouped by the shape of its carbon chain, whether it's an open chain, a ring, or contains other atoms in the ring. This classification helps in understanding their properties and reactions.
In simple words: Compounds are sorted by how their carbon atoms are linked: in a straight line, a closed ring, or a ring with other atoms too. This helps us understand what they are like.

🎯 Exam Tip: Practice drawing the structural formulas and identifying the classification of common organic compounds, especially cyclic and heterocyclic structures.

Question 3. How is ethanoic acid prepared from ethanol? Give the chemical equation.
Answer: Ethanol is oxidized to ethanoic acid using an alkaline potassium permanganate (\(\text{KMnO}_4\)) solution or an acidified potassium dichromate (\(\text{K}_2\text{Cr}_2\text{O}_7\)). This is an oxidation reaction where ethanol gains oxygen atoms.
\( \text{CH}_3\text{CH}_2\text{OH} + 2[\text{O}] \xrightarrow{\text{H}^+/\text{K}_2\text{Cr}_2\text{O}_7} \text{CH}_3\text{COOH} + \text{H}_2\text{O} \)
In simple words: You can make ethanoic acid from ethanol by adding an oxidizing agent like acidified potassium dichromate. This chemical change adds oxygen to the ethanol, turning it into ethanoic acid.

🎯 Exam Tip: Remember that primary alcohols like ethanol can be oxidized to carboxylic acids using strong oxidizing agents such as acidified potassium dichromate or alkaline potassium permanganate.

Question 4. How do detergents cause water pollution? Suggest remedial measures to prevent this pollution?
Answer: Detergents can cause water pollution in a couple of ways.
• Some detergents have branched hydrocarbon chains that are difficult for microorganisms in water to break down. This means they are not fully biodegradable and stay in the water, causing pollution.
• To prevent this, biodegradable detergents are made with straight hydrocarbon chains. These are easier for microorganisms to break down and remove from the water, reducing their polluting effect. Developing advanced wastewater treatment plants is also a crucial step.
In simple words: Some detergents pollute water because tiny bugs cannot break them down easily. We can fix this by using detergents that have simpler chemical chains, which the bugs can eat up.

🎯 Exam Tip: Focus on the biodegradability of detergents related to their hydrocarbon chain structure (branched vs. straight) and link it to environmental impact and remedial measures.

Question 5. Differentiate soaps and detergents.
Answer:

Soaps and detergents both clean, but they are made differently and work best in different conditions. This difference in chemical structure, particularly the ionic part, is what gives them distinct properties and uses.
In simple words: Soaps are made from fats and don't work well in hard water, creating scum. Detergents are made from crude oil, work well in hard water without scum, and can foam a lot.

🎯 Exam Tip: Create a mental table of key differences between soaps and detergents based on their chemical composition, behavior in hard water, and biodegradability.

VI. Long answer questions.

Question 1. What is called a homologous series? Give any three of its characteristics?
Answer: A homologous series is a group or a class of organic compounds that share the same general formula and similar chemical properties. In such a series, successive members differ by a \(-\text{CH}_2\) group. This allows for predictable properties within the series.
Characteristics of homologous series:
• All members of a homologous series contain the same elements and functional group.
• All members of a homologous series can be prepared by a common method.
• The physical properties, like melting and boiling points, generally show a gradual change as the molecular mass increases.
In simple words: A homologous series is a group of chemicals that are alike because they have the same formula pattern and similar traits, with each member differing by a small \(-\text{CH}_2\) unit.

🎯 Exam Tip: Focus on the definition of a homologous series and its three main characteristics: same functional group, common general formula, and a \(-\text{CH}_2\) difference between successive members.

Question 2. Arrive at, systematically, the IUPAC name of the compound: CH3-CH2-CH2-OH.
Answer: To name the compound \( \text{CH}_3-\text{CH}_2-\text{CH}_2-\text{OH} \) using IUPAC rules, we follow these steps:
Step 1: The longest continuous chain contains 3 carbon atoms. The root word for three carbons is 'Prop'.
Step 2: There are only single bonds between the carbon atoms in the chain, so the primary suffix is 'ane'.
Step 3: The compound has an -OH (hydroxyl) group, which means it is an alcohol. The carbon chain is numbered starting from the end closest to the -OH group. In this case, it is carbon 1.
\( \overset{3}{\text{CH}}_3-\overset{2}{\text{CH}}_2-\overset{1}{\text{CH}}_2-\text{OH} \)
Step 4: The locant number for the -OH group is 1, so the secondary suffix becomes '1-ol'.
Combining these parts, the name of the compound is Prop + ane + (1-ol) = Propan-1-ol. This systematic naming ensures a unique name for each compound.
In simple words: To name \( \text{CH}_3-\text{CH}_2-\text{CH}_2-\text{OH} \), count the three carbons (Prop), see only single bonds (ane), and note the -OH group on the first carbon (1-ol). Put it together, and it is Propan-1-ol.

🎯 Exam Tip: Practice IUPAC naming by breaking down compounds into their root word (carbon chain length), primary suffix (bond saturation), and secondary suffix (functional group and its position).

Question 3. How is ethanol manufactured from sugarcane?
Answer: Ethanol is made in factories from molasses, which is a thick, dark syrup left over after sugar is removed from sugarcane juice. Molasses has about 30% sucrose that cannot be crystallized. It is turned into ethanol through these steps:
(i) Dilution of molasses: First, molasses is mixed with water until the sugar concentration is about 8 to 10 percent. This makes it suitable for yeast activity.
(ii) Addition of Nitrogen source: Molasses usually has enough nitrogen compounds to feed yeast. If not, substances like ammonium sulphate or ammonium phosphate are added to boost the nitrogen content.
(iii) Addition of Yeast: The diluted molasses, enriched with nitrogen, is put into large tanks, and yeast is added. The mixture is kept at about 303K for a few days. During this time, enzymes from the yeast (invertase and zymase) convert the sucrose in molasses into glucose and fructose, and then into ethanol and carbon dioxide.
\( \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \xrightarrow{\text{invertase}} \text{C}_6\text{H}_{12}\text{O}_6 + \text{C}_6\text{H}_{12}\text{O}_6 \) (Sucrose into Glucose and Fructose)
\( \text{C}_6\text{H}_{12}\text{O}_6 \xrightarrow{\text{zymase}} 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 \) (Glucose/Fructose into Ethanol and Carbon Dioxide)
The liquid after this step is called 'wash'.
(iv) Distillation of 'Wash': The 'wash', which has 15 to 18 percent alcohol, is then put through fractional distillation. This separates the alcohol from water. The main part collected is rectified spirit (95.5% ethanol and 4.5% water). To get pure alcohol (100%), or absolute alcohol, this mixture is heated with quicklime for 5-6 hours and then distilled again. This process is called fermentation, a crucial part of brewing and ethanol production.
In simple words: Ethanol is made from sugary molasses, a leftover from sugarcane. Molasses is diluted, yeast is added, and it ferments into a low-alcohol liquid. Then, distillation cleans and concentrates the alcohol.

🎯 Exam Tip: Understand the entire fermentation process for ethanol production, including the role of molasses, yeast enzymes (invertase, zymase), and the final distillation steps.

Question 4. Give the balanced chemical equation of the following reactions:
(i) Neutralization of NaOH with ethanoic acid.
(ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO3.
(iii) Oxidation of ethanol by acidified potassium dichromate.
(iv) Combustion of ethanol.
Answer:
(i) Neutralization of NaOH with ethanoic acid:
\( \text{CH}_3\text{COOH} + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{H}_2\text{O} \)
(Ethanoic acid + Sodium hydroxide \( \rightarrow \) Sodium ethanoate + Water)
(ii) Evolution of carbon dioxide by the action of ethanoic acid with \( \text{NaHCO}_3 \):
\( \text{CH}_3\text{COOH} + \text{NaHCO}_3 \rightarrow \text{CH}_3\text{COONa} + \text{CO}_2 \uparrow + \text{H}_2\text{O} \)
(Ethanoic acid + Sodium bicarbonate \( \rightarrow \) Sodium ethanoate + Carbon dioxide + Water)
(iii) Oxidation of ethanol by acidified potassium dichromate:
\( \text{CH}_3\text{CH}_2\text{OH} + 2[\text{O}] \xrightarrow{\text{H}^+/\text{K}_2\text{Cr}_2\text{O}_7} \text{CH}_3\text{COOH} + \text{H}_2\text{O} \)
(Ethanol + Oxygen atoms \( \rightarrow \) Ethanoic acid + Water)
(iv) Combustion of ethanol:
\( \text{C}_2\text{H}_5\text{OH} + 3\text{O}_2 \rightarrow 2\text{CO}_2 \uparrow + 3\text{H}_2\text{O} \)
(Ethanol + Oxygen \( \rightarrow \) Carbon dioxide + Water)
These equations show how different types of reactions—neutralization, gas evolution, oxidation, and combustion—happen with common organic compounds.
In simple words: These are chemical recipes for how ethanoic acid reacts with a base (NaOH) and baking soda (\( \text{NaHCO}_3 \)), and how ethanol changes when it is oxidized or burned with oxygen.

🎯 Exam Tip: Master balancing chemical equations and understanding the reactants and products for common organic reactions like neutralization, oxidation, and combustion.

Question 1. The molecular formula of an alcohol is C4H10O. The locant number of its -OH group is 2.
(i) Draw its structural formula.
(ii) Give its IUPAC name.
(iii) Is it saturated or unsaturated?
Answer:
(i) Structural formula:
\( \text{CH}_3-\text{CH}-\text{CH}_2-\text{CH}_3 \)
\( \hspace{1.5cm} | \)
\( \hspace{1.5cm} \text{OH} \)
(ii) IUPAC name: Butan-2-ol. This name indicates a 4-carbon chain (butan) with a hydroxyl group on the second carbon (2-ol).
(iii) The compound is saturated. All carbon-carbon bonds are single bonds, and there are no double or triple bonds.
In simple words: For an alcohol with formula C4H10O and the -OH on the second carbon, its structure is a four-carbon chain with the alcohol group in the middle. It's called Butan-2-ol, and because it has only single bonds, it is saturated.

🎯 Exam Tip: When drawing structural formulas from a molecular formula and locant number, ensure all carbon valencies (4 bonds) are satisfied and the functional group is placed correctly.

Question 2. An organic compound 'A' is widely used as a preservative and has the molecular formula C2H4O2. This compound reacts with ethanol to form a sweet smelling compound 'B'.
(i) Identify the compound 'A'.
(ii) Write the chemical equation for its reaction with ethanol to form compound 'B'.
(iii) Name the process.
Answer:
(i) Compound 'A' is acetic acid (or) ethanoic acid. Its molecular formula \( \text{C}_2\text{H}_4\text{O}_2 \) matches, and it is a common food preservative.
\( \text{A} = \text{CH}_3\text{COOH} \)
(ii) Chemical equation for reaction with ethanol to form compound 'B':
\( \text{CH}_3\text{COOH} + \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \)
Here, 'B' is ethyl ethanoate, which is an ester and has a sweet smell. Concentrated sulphuric acid acts as a dehydrating agent in this reversible reaction.
(iii) The process is called Esterification.
In simple words: Compound 'A' is ethanoic acid, a preservative. When it reacts with ethanol, it makes a sweet-smelling substance called ethyl ethanoate, and this process is called esterification.

🎯 Exam Tip: Recognize ethanoic acid as a common preservative and associate its reaction with alcohol to form a sweet-smelling ester with the process of esterification. This is a crucial reaction in organic chemistry.

I. Choose the best answer.

Question 1. The general formula of alkane series is:
(a) \( \text{C}_\text{n}\text{H}_{2\text{n}} \)
(b) \( \text{C}_\text{n}\text{H}_{2\text{n}-1} \)
(c) \( \text{C}_\text{n}\text{H}_{2\text{n}+2} \)
(d) \( \text{C}_\text{n}\text{H}_{2\text{n}-2} \)
Answer: (c) \( \text{C}_\text{n}\text{H}_{2\text{n}+2} \)
In simple words: The formula \( \text{C}_\text{n}\text{H}_{2\text{n}+2} \) always tells you the correct number of hydrogen atoms for any alkane, which are organic compounds with only single bonds. This formula helps predict the molecular structure of any straight-chain or branched alkane.

🎯 Exam Tip: Memorize the general formulas for alkanes, alkenes, and alkynes (\( \text{C}_\text{n}\text{H}_{2\text{n}+2} \), \( \text{C}_\text{n}\text{H}_{2\text{n}} \), \( \text{C}_\text{n}\text{H}_{2\text{n}-2} \) respectively) as they are fundamental in organic chemistry.

Question 2. Organic compounds are ______ in nature.
(a) flammable
(b) inflammable
(c) heavy
(d) dissolving
Answer: (b) inflammable
In simple words: Most organic compounds can easily catch fire and burn, meaning they are inflammable. This property is due to their carbon and hydrogen composition, which readily oxidizes.

🎯 Exam Tip: Note that "flammable" and "inflammable" mean the same thing: easily set on fire. It's a common characteristic of many organic compounds.

Question 3. The Heterocyclic compound is:
(a) Benzene
(b) Pyridine
(c) Naphthalene
(d) Camphor
Answer: (b) Pyridine
In simple words: Pyridine has a ring structure where one carbon atom is replaced by a nitrogen atom. This makes it a heterocyclic compound, unlike the others which are purely carbon-based aromatic or non-aromatic structures.

🎯 Exam Tip: Remember that heterocyclic compounds contain at least one atom other than carbon in their ring structure.

Question 4. Pick out the unsaturated compound from the following
(a) \( \text{CH}_3-\text{CH}_2-\text{CH}_3 \)
(b) \( \text{CH}_3-\text{CH}=\text{CH}_2 \)
(c) \( \text{CH}_3-\text{C} \equiv \text{CH} \)
(d) both (b) and (c).
Answer: (d) both (b) and (c)
In simple words: Unsaturated compounds have double or triple bonds between carbon atoms. Propane (\( \text{CH}_3-\text{CH}_2-\text{CH}_3 \)) only has single bonds, making it saturated. Propene (\( \text{CH}_3-\text{CH}=\text{CH}_2 \)) has a double bond, and propyne (\( \text{CH}_3-\text{C} \equiv \text{CH} \)) has a triple bond, so both are unsaturated.

🎯 Exam Tip: Saturated compounds have only single bonds, while unsaturated compounds contain at least one double or triple bond, which allows them to react with substances like bromine water.

Question 5. ______ will decolourise \( \text{Br}_2/\text{H}_2\text{O} \).
(a) Methane
(b) Pent-2-ene
(c) Ethyl alcohol
(d) Ethanal
Answer: (b) Pent-2-ene
In simple words: Only chemicals with double or triple bonds (unsaturated) can remove the color from bromine water. Pent-2-ene has a double bond, so it changes the color by reacting with bromine.

🎯 Exam Tip: The decolorization of bromine water is a classic test to identify the presence of unsaturation (carbon-carbon double or triple bonds) in organic compounds.

Question 6. The simplest alkane is ______.
(a) Ethane
(b) Ethyne
(c) Propane
(d) Methane.
Answer: (d) Methane.
In simple words: Alkanes are simple carbon compounds. The smallest one, with just one carbon atom (\( \text{CH}_4 \)), is called methane.

🎯 Exam Tip: Always remember the general formulas for alkanes, alkenes, and alkynes to quickly identify their members.

Question 7. ______ is the prefix used for \( -\text{NH}_2 \) Group.
(a) Fluoro
(b) Methyl
(c) Amino
(d) Nitro
Answer: (c) Amino
In simple words: When an \( -\text{NH}_2 \) group is part of a chemical name, "amino" is the word you put in front to show it's there.

🎯 Exam Tip: Knowing common prefixes and suffixes for functional groups is crucial for correct IUPAC nomenclature.

Question 8. The IUPAC name of an organic compound is Pentan-2-one. The secondary suffix is:
(a) Pentan
(b) an
(c) -one
(d) -2-
Answer: (c) -one
In simple words: The ending part of a chemical name tells you what type of family it belongs to. For ketones, like Pentan-2-one, the ending is "-one".

🎯 Exam Tip: Identify the functional group first to determine the correct secondary suffix for IUPAC naming.

Question 9. Which of the following can be used to increase the nitrogen content?
(a) \( (\text{NH}_4)_2\text{SO}_4 \) (or) \( (\text{NH}_4)_3\text{PO}_4 \)
(b) \( (\text{NH}_4)_2\text{CO}_3 \) (or) \( \text{NH}_4\text{Cl} \)
(c) \( (\text{NH}_4)_2\text{CO}_3 \) (or) \( \text{NH}_4\text{OH} \)
(d) None of the options
Answer: (a) \( (\text{NH}_4)_2\text{SO}_4 \) (or) \( (\text{NH}_4)_3\text{PO}_4 \)
In simple words: To add more nitrogen, we can use chemicals that have ammonium in them, like ammonium sulfate or ammonium phosphate. These are good for plants as fertilizers.

🎯 Exam Tip: Ammonium salts are frequently used as nitrogen sources in fertilizers because they contain the easily absorbed ammonium ion.

Question 10. Which one of the following is a general formula for alkyne?
(a) \( \text{C}_\text{n}\text{H}_{2\text{n}} \)
(b) \( \text{C}_\text{n}\text{H}_{2\text{n}+2} \)
(c) \( \text{C}_\text{n}\text{H}_{2\text{n}-2} \)
(d) \( \text{C}_\text{n}\text{H}_\text{n} \)
Answer: (c) \( \text{C}_\text{n}\text{H}_{2\text{n}-2} \)
In simple words: Alkynes are a type of carbon compound with a special triple bond. Their general rule for atoms is 'n' carbons and '2n minus 2' hydrogens.

🎯 Exam Tip: Distinguish clearly between the general formulas for alkanes (\( \text{C}_\text{n}\text{H}_{2\text{n}+2} \)), alkenes (\( \text{C}_\text{n}\text{H}_{2\text{n}} \)), and alkynes (\( \text{C}_\text{n}\text{H}_{2\text{n}-2} \)).

II. Fill in the blanks.

Question. Fill in the blanks.
1. The common difference between the successive members of a homologous series is ______.
2. Denatured spirit is a mixture of ethanol and ______.
3. Methane gas is produced when the sodium salt of ethanoic acid is ______ with soda lime.
4. For coagulating rubber from latex ______ is used.
5. ______ is added to prevent the caking of the detergent powder.
6. When a soap or detergent is added to water, the molecular clusters together to form ______.
7. The terminal functional group among aldehydes and ketones is ______.
8. On dehydrogenation of ethanol with Cu/573 K it gives ______ gas.
9. ______ converts glucose into ethanol and carbondi-oxide.
10. The IUPAC name of the compound with molecular formula \( \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COOH} \) is ______.
Answer:
1. \( -\text{CH}_2 \)
2. pyridine
3. decarboxylated
4. ethanoic acid
5. \( \text{Na}_2\text{SO}_4 \) or Sodium sulphate
6. micelles
7. aldehyde
8. \( \text{H}_2 \)
9. Zymase
10. Pentanoic acid
In simple words: Each step in a homologous series adds a \( -\text{CH}_2 \) group. Denatured spirit is ethanol mixed with pyridine. Methane gas is made when ethanoic acid is decarboxylated. Ethanoic acid helps rubber to clot. Sodium sulfate stops detergents from forming clumps. When soap is added to water, it forms tiny groups called micelles. The functional group at the end for aldehydes and ketones is aldehyde. Ethanol loses hydrogen to form \( \text{H}_2 \) gas. Zymase changes glucose into ethanol and carbon dioxide. The compound \( \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COOH} \) is called pentanoic acid.

🎯 Exam Tip: Review the definitions of homologous series, denaturation, decarboxylation, and IUPAC nomenclature for organic acids.

III Match the following:

Question 1. Match the Column I and Column II.

Answer:
A. (ii)
B. (iii)
C. (v)
D. (i)
E. (iv)
In simple words: Alkenes are compounds that are unsaturated because they have double bonds. Carboxylic acids have names ending in '-oic acid'. Carbon has a valency of four, meaning it can form four bonds. Cyclobutane is an alicyclic compound because it forms a ring of carbon atoms. Ethers are often used as pain killers in some medical applications.

🎯 Exam Tip: Practice identifying functional groups, their properties, and common uses to quickly match them.

IV. Assertion and Reason:

Question 1. Assertion: Alkynes decolourise bromine water. Reason: Alkynes are unsaturated compounds.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: Both statements are true. Alkynes change the color of bromine water because they are unsaturated, meaning they have triple bonds that can react with bromine. The reason correctly tells us why the assertion is true.

🎯 Exam Tip: For assertion-reason questions, first determine if each statement is true, then check if the reason logically explains the assertion.

Question 2. Assertion: Denaturation of ethanol makes it unfit for drinking purpose. Reason: Ethanol is mixed with Pyridine for denaturation.
(a) Assertion and Reason are correct, Reason explains the Assertion.
Answer: (a) Assertion and Reason are correct, Reason explains the Assertion.
In simple words: Both statements are correct. Ethanol is made undrinkable (denatured) by adding substances like pyridine to it. The pyridine makes it toxic and prevents it from being consumed as an alcoholic drink.

🎯 Exam Tip: Denaturation is an important process to prevent the misuse of ethanol; know the common denaturing agents like pyridine.

Question 3. Assertion: Organic compounds contain covalent bonds. Reason: Organic compounds have low melting and boiling points.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (d) Assertion and Reason are correct, Reason doesn't explains Assertion.
In simple words: Both statements are true. Organic compounds do have covalent bonds, and they also tend to have low melting and boiling points. However, the reason (low melting/boiling points) does not directly explain why they have covalent bonds. Covalent bonds explain the low melting point, not the other way around.

🎯 Exam Tip: Understand that while both statements might be true, the reason must *explain* the assertion for option (a) to be correct. Low melting points in organic compounds are a *consequence* of their covalent bonding, not a reason for it.

Question 4. Assertion: Due to catenation a large number of carbon compounds are formed. Reason: Carbon compounds show the property of allotropy.
(a) Assertion and Reason are correct, Reason explains the Assertion.
(b) Assertion is correct, Reason is wrong.
(c) Assertion is wrong, Reason is correct.
(d) Assertion and Reason are correct, Reason doesn't explains Assertion.
Answer: (b) Assertion is correct, Reason is wrong.
In simple words: The first statement is true: carbon can link with itself in many ways (catenation), making countless compounds. The second statement is false; while some carbon forms like diamond and graphite show allotropy, this is not the reason for the vast number of carbon compounds. Catenation is the actual reason.

🎯 Exam Tip: Catenation is the unique ability of carbon atoms to form long chains and rings, which is the primary reason for the vast diversity of organic compounds. Allotropy refers to different structural forms of an element.

V. Short answer questions:

Question 1. Define isomerism with an example.
Answer: Isomerism is a phenomenon where organic compounds have the same molecular formula but different structural formulas. For example, the molecular formula \( \text{C}_2\text{H}_6\text{O} \) can represent two different compounds: ethanol (\( \text{CH}_3\text{CH}_2\text{OH} \)) and methoxy methane (\( \text{CH}_3\text{OCH}_3 \)). These compounds have different properties despite having the same atomic count. Each isomer represents a unique arrangement of atoms.
In simple words: Isomerism is when two or more chemicals have the same list of atoms (like \( \text{C}_2\text{H}_6\text{O} \)) but are put together in different ways. For example, ethanol and methoxy methane both have two carbons, six hydrogens, and one oxygen, but they are arranged differently.

🎯 Exam Tip: When defining isomerism, always provide a clear example with both the molecular formula and the structural formulas of the isomers.

Question 2. What are root words?
Answer: Root words are the main part of an IUPAC name for an organic compound. They tell us about the number of carbon atoms in the longest continuous chain (the parent chain) of the compound. They also give a basic idea of how these carbon atoms are arranged. For example, 'meth-' for one carbon, 'eth-' for two, 'prop-' for three, and so on.
In simple words: Root words in chemistry names tell us how many carbon atoms are in the longest chain of a chemical. Like 'meth' means one carbon, 'eth' means two carbons.

🎯 Exam Tip: Knowing the root words for carbon chain lengths (meth-, eth-, prop-, but-, pent-, hex-, etc.) is fundamental to IUPAC naming.

Question 3. Write the functional group and the secondary suffix of the following compounds.

Answer: The table above shows the common functional groups and their corresponding secondary suffixes for different classes of organic compounds. Each functional group gives the compound its characteristic properties and determines how it is named in the IUPAC system. This systematic naming helps to accurately describe the chemical structure.
In simple words: The table lists special groups of atoms (functional groups) and the endings (suffixes) we use in names for chemicals like alcohols, aldehydes, ketones, and carboxylic acids. These endings help us know what kind of chemical it is.

🎯 Exam Tip: Memorize the functional groups and their IUPAC suffixes for common organic compound classes; this is a frequent examination topic.

Question 4. What happens when ethanol is dehydrated with concentrated \( \text{H}_2\text{SO}_4 \) at 443K?
Answer: When ethanol is heated with concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)) at 443 Kelvin, a dehydration reaction occurs. In this process, the ethanol molecule loses a molecule of water. This leads to the formation of ethene, which is an alkene. Concentrated sulfuric acid acts as a dehydrating agent.
\[ \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Conc.H}_2\text{SO}_4 \text{ at } 443\text{K}} \text{CH}_2=\text{CH}_2 + \text{H}_2\text{O} \]
In simple words: If you heat ethanol with strong sulfuric acid, it loses water and turns into ethene. Think of the acid pulling the water out.

🎯 Exam Tip: Remember the specific conditions (temperature and catalyst) for dehydration reactions, as they are crucial for determining the product formed (e.g., ethene vs. ether formation at different temperatures).

Question 5. Write a note on esterification.
Answer: Esterification is a chemical reaction where an alcohol reacts with a carboxylic acid to form an ester, a compound often recognized by its characteristic fruity smell. This reaction typically occurs in the presence of a strong acid catalyst, such as concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)), which also acts as a dehydrating agent. For example, when ethanol reacts with ethanoic acid, ethyl ethanoate is formed.
\[ \text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{COOH} \xrightarrow{\text{conc.H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \]
In simple words: Esterification is when an alcohol and an acid join together to make a new chemical called an ester, which smells like fruit. This process needs a strong acid to help it happen.

🎯 Exam Tip: Esters are easily identified by their fruity fragrance, a key property to remember for identifying products of esterification.

Question 6. Write tests to identify the presence of ethanoic acid.
Answer: There are several tests to identify the presence of ethanoic acid:
1. Ethanoic acid turns blue litmus paper red, indicating its acidic nature. This is a general test for acids.
2. It causes brisk effervescence (fizzing) when treated with sodium carbonate (\( \text{Na}_2\text{CO}_3 \)) because carbon dioxide gas is released. This reaction is typical for carboxylic acids.
3. Ethanoic acid produces a sweet-smelling compound (an ester) when it reacts with ethanol, especially in the presence of a catalyst. This specific esterification reaction confirms its identity.
In simple words: You can find ethanoic acid in a few ways: it makes blue litmus paper red; it fizzes when you add baking soda (sodium carbonate); and it smells sweet like fruit if you mix it with alcohol.

🎯 Exam Tip: Remember both general tests for acids (litmus, carbonate reaction) and specific reactions (esterification) to confidently identify ethanoic acid.

Question 7. Write a note on decarboxylation reaction.
Answer: Decarboxylation is a chemical reaction that involves the removal of a carboxyl group (\( -\text{COOH} \)) from a compound, typically in the form of carbon dioxide (\( \text{CO}_2 \)). A common example is when a sodium salt of ethanoic acid (sodium acetate) is heated with soda lime (a solid mixture of sodium hydroxide, \( \text{NaOH} \), and calcium oxide, \( \text{CaO} \)). This process yields methane gas.
\[ \text{CH}_3\text{COONa} \xrightarrow{\text{NaOH/CaO}} \text{CH}_4\uparrow + \text{Na}_2\text{CO}_3 \]
In simple words: Decarboxylation is a reaction where a chemical loses a \( \text{CO}_2 \) part. For example, if you heat sodium ethanoate with soda lime, it forms methane gas.

🎯 Exam Tip: Decarboxylation is an important method for shortening carbon chains and is often used in the preparation of alkanes from carboxylic acids.

Question 8. What is hard soap?
Answer: Hard soaps are a type of soap typically prepared through a process called saponification. This involves the reaction of oils or fats with caustic soda (sodium hydroxide, \( \text{NaOH} \)). These soaps are solid and are commonly used for general washing and cleaning purposes. The nature of the alkali (sodium hydroxide) used in their production contributes to their hardness. They form a good lather and are effective in cleaning.
In simple words: Hard soaps are made by mixing oils or fats with a strong chemical called sodium hydroxide. They are solid and are used for cleaning.

🎯 Exam Tip: Remember that hard soaps are typically sodium salts of fatty acids, distinguishing them from soft soaps (potassium salts).

Question 9. Why ordinary soap is not suitable for using with hard water?
Answer: Ordinary soaps are not ideal for use with hard water because hard water contains high levels of dissolved mineral salts, primarily calcium and magnesium ions. When ordinary soap comes into contact with these ions, it reacts to form an insoluble precipitate known as scum. This sticky, grey scum floats on the water's surface and deposits on clothes or tubs, making the cleaning process ineffective and leaving residues. Therefore, the cleansing action of soap is significantly reduced in hard water. This is why detergents are often preferred in hard water areas.
In simple words: Regular soap doesn't work well with hard water because hard water has minerals like calcium and magnesium. These minerals mix with the soap to form a sticky 'scum' that doesn't clean well and leaves marks.

🎯 Exam Tip: The formation of insoluble scum (calcium and magnesium salts of fatty acids) is the key reason why ordinary soaps are ineffective in hard water.

Question 10. What are the advantages of detergents over soaps?
Answer: Detergents offer several advantages over traditional soaps:
1. They work well in both hard and soft water and clean more effectively in hard water because they do not form scum. They do not react with calcium or magnesium ions to form precipitates.
2. Detergents can also be used in salty and acidic water, maintaining their cleaning power.
3. Unlike soaps, detergents do not leave behind any soap scum on surfaces like tubs or clothes, ensuring a cleaner finish.
4. They dissolve easily even in cool water and rinse off completely, leaving no residue.
5. Detergents are suitable for washing delicate items like woollen garments, a task for which soap is often unsuitable.
6. Most modern detergents have linear hydrocarbon chains, making them biodegradable and more environmentally friendly.
7. They act as active emulsifiers, meaning they are very effective at breaking down and removing tough substances like motor grease.
8. Detergents provide powerful and safe cleaning, helping to keep synthetic fabrics looking brighter and whiter.
In simple words: Detergents clean better in hard and soft water, don't leave scum, work in salty or acidic water, dissolve easily, are safe for wool, are often biodegradable, cut through grease, and keep clothes bright and clean.

🎯 Exam Tip: Focus on the key differences: detergents' effectiveness in hard/acidic water, lack of scum formation, and biodegradability (for modern ones) as primary advantages.

Question 1. Write the IUPAC name of the following compounds.

Answer: The table provides the IUPAC names for the given organic compounds, which are systematically determined based on their longest carbon chain and functional groups. For example, propanone is a ketone with three carbon atoms, and methanal is the simplest aldehyde with one carbon atom. Correctly naming these compounds helps in understanding their structure and properties.
In simple words: The table above shows the correct scientific names for different chemicals, like propanone, ethanal, butanoic acid, hexan-3-one, and methanal. These names help scientists understand what the chemicals are made of.

🎯 Exam Tip: Practice IUPAC nomenclature regularly, paying close attention to identifying the parent chain, functional groups, and numbering rules for substituents.

Question 2. Write the characteristics of organic compounds.
Answer: Organic compounds have several distinct characteristics:
1. They often have high molecular weights and complex structures, which contribute to their diverse properties.
2. Most organic compounds are insoluble in water but readily dissolve in organic solvents like ether, carbon tetrachloride, and toluene. This is because "like dissolves like".
3. Many organic compounds are highly inflammable, meaning they burn easily, often producing carbon dioxide and water.
4. They are generally less reactive compared to inorganic compounds, leading to slower reaction rates. This allows for more controlled chemical synthesis.
5. Organic compounds primarily form covalent bonds, where atoms share electrons, rather than ionic bonds.
6. They typically exhibit lower melting and boiling points compared to inorganic compounds, due to weaker intermolecular forces.
7. Organic compounds frequently display isomerism, where a single molecular formula can represent multiple compounds with different physical and chemical properties.
8. Many organic compounds are volatile, meaning they can easily vaporize at room temperature.
9. Organic compounds can often be synthesized (prepared) in laboratory settings.
In simple words: Organic compounds are usually large and complex. They don't mix well with water but dissolve in other special liquids. Many catch fire easily. They react slower than non-organic chemicals. They share electrons to form bonds. They usually melt and boil at lower temperatures. They can have the same atoms but different shapes (isomerism). Many turn into gas easily. We can make them in labs.

🎯 Exam Tip: When listing characteristics, aim for a comprehensive set that covers physical properties, bonding, reactivity, and structural diversity like isomerism.

Question 3. List the advantages of detergents over soaps.
Answer: Detergents have several benefits when compared to soaps:
1. They work well in both hard and soft water and clean more effectively in hard water because they do not form scum.
2. Detergents can also be used in salty and acidic water, maintaining their cleaning power.
3. Unlike soaps, detergents do not leave behind any soap scum on tubs or clothes, ensuring a cleaner finish.
4. They dissolve easily in cool water and rinse off completely, leaving no residue.
5. Detergents are suitable for washing woollen garments, a task for which soap is often unsuitable.
6. Modern detergents typically have linear hydrocarbon chains, making them biodegradable and more environmentally friendly.
7. They are effective emulsifiers, meaning they are good at breaking down and removing tough substances like motor grease.
8. Detergents provide powerful and safe cleaning, helping to keep synthetic fabrics looking brighter and whiter.
In simple words: Detergents clean better in hard and soft water, don't leave scum, work in salty or acidic water, dissolve easily, are safe for wool, are often biodegradable, cut through grease, and keep clothes bright and clean.

🎯 Exam Tip: The ability to function in hard water without forming scum is the most significant advantage of detergents over soaps; always highlight this point.

Question 4. Draw the schematic diagram for the classification of organic compounds based on the pattern of carbon chain with example.
Answer: Organic compounds are classified based on their carbon chain structure into acyclic (open chain) and cyclic (closed chain) compounds. Cyclic compounds are further divided into carbocyclic and heterocyclic, and carbocyclic compounds are split into alicyclic and aromatic. This classification helps in understanding the structural diversity and properties of various organic molecules.

In simple words: Organic chemicals can be grouped by how their carbon atoms are linked. They can be open chains or closed rings. Rings can be all carbon (carbocyclic) or have other atoms too (heterocyclic). Carbocyclic rings can be simple (alicyclic) or special like benzene (aromatic). Open chains can have only single bonds (saturated) or double/triple bonds (unsaturated).

🎯 Exam Tip: When drawing classification diagrams, ensure clear distinctions between categories and provide relevant examples for each type of compound.

Question 5. Explain the manufacture of soap.
Answer: The manufacturing of soap, particularly hard soap, traditionally follows the Kettle Process, which is one of the oldest methods and is still used today for small-scale production. This process primarily involves two main steps:
1. Saponification of oil: In this step, oils or fats are placed in a large iron kettle. An alkaline solution, usually 10% caustic soda (sodium hydroxide), is slowly added in a slight excess. The mixture is then heated and boiled by passing steam through it. Over several hours of boiling, the oil undergoes hydrolysis, meaning it reacts with the alkali to break down into soap (sodium salt of fatty acids) and glycerol. This entire reaction is known as saponification.
2. Salting out of soap: After saponification, common salt (sodium chloride) is added to the boiling mixture. The addition of salt reduces the solubility of the soap in the water, causing it to precipitate out. The soap then rises to the top of the liquid mixture, forming a thick, curdy mass. This 'neat soap' is collected and allowed to cool, after which it can be processed further into bars. This method ensures efficient separation of the pure soap.
In simple words: Making soap, especially hard soap, involves two steps. First, oils are boiled with a strong alkaline liquid like caustic soda; this process is called saponification. Second, salt is added to the boiled mixture, which makes the soap float to the top as a thick layer, separate from the water. This is called salting out.

🎯 Exam Tip: Understand that saponification is essentially the hydrolysis of an ester (fat/oil) in the presence of an alkali, and salting out is a separation technique based on solubility changes.

Question 6. Ethanol is heated with excess concentrated \( \text{H}_2\text{SO}_4 \) at 443K.
(a) Name the reaction that occurs and explain it.
(b) Provide the chemical equation for the reaction.
(c) What is the product formed? What happens when this gas is passed through \( \text{Br}_2/\text{H}_2\text{O} \).
(d) Why does no decolourization occur when ethanol is treated with \( \text{Br}_2/\text{H}_2\text{O} \)?
Answer:
(a) The reaction that occurs is called Dehydration (Loss of water). When ethanol is heated with concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)) at a temperature of 443 Kelvin, it loses a molecule of water from its structure. This specific condition causes ethanol to be converted into ethene, an unsaturated hydrocarbon. Concentrated sulfuric acid acts as a powerful dehydrating agent, removing the water molecule. This is a common method for producing alkenes from alcohols.
(b) The chemical equation for the dehydration of ethanol to ethene is:
\[ \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Conc.H}_2\text{SO}_4 \text{ at } 443\text{K}} \text{CH}_2=\text{CH}_2 + \text{H}_2\text{O} \]
(c) The product formed is ethene gas. When ethene gas is passed through bromine water (\( \text{Br}_2/\text{H}_2\text{O} \)), it causes the bromine water to decolorize. This happens because ethene, being an unsaturated compound with a carbon-carbon double bond, undergoes an addition reaction with bromine, consuming the bromine and removing its characteristic color. This is a common test for unsaturation.
(d) Decolourization does not occur when ethanol is treated with bromine water (\( \text{Br}_2/\text{H}_2\text{O} \)) because ethanol is a saturated compound. It contains only carbon-carbon single bonds, and therefore, it cannot undergo the addition reaction with bromine that unsaturated compounds like ethene can. Saturated compounds generally do not react with bromine water under normal conditions.
In simple words: (a) When ethanol is heated with strong sulfuric acid, it loses water in a process called dehydration. (b) This makes ethene gas and water. (c) The ethene gas is the product, and it will remove the color from bromine water because it has a double bond. (d) Ethanol itself won't change the color of bromine water because it only has single bonds and can't react in the same way.

🎯 Exam Tip: Distinguish between the reactions of saturated and unsaturated compounds with bromine water; this is a fundamental test in organic chemistry.

VII. Hot Questions.

Question 1. Organic compounds A and B are isomers with the molecular formula \( \text{C}_2\text{H}_6\text{O} \). (A) liberates \( \text{H}_2 \) gas when it reacts with metallic sodium whereas (B) does not. Compound (A) reacts with ethanoic acid and forms a fruity smelling compound (C). Identify A, B and C and explain the reactions.
Answer:
Given that compounds A and B are isomers with the molecular formula \( \text{C}_2\text{H}_6\text{O} \), and knowing their reactions, we can identify them:
1. Compound (A) reacts with metallic sodium to liberate \( \text{H}_2 \) gas. This is a characteristic reaction of alcohols, where the hydrogen of the \( -\text{OH} \) group is replaced by sodium. Thus, (A) is ethanol (\( \text{CH}_3\text{CH}_2\text{OH} \)).
\[ 2\text{CH}_3\text{CH}_2\text{OH} + 2\text{Na} \rightarrow 2\text{CH}_3\text{CH}_2\text{ONa} + \text{H}_2\uparrow \]
2. Compound (B) does not react with metallic sodium. This indicates that it is not an alcohol. Given that it is an isomer of ethanol with formula \( \text{C}_2\text{H}_6\text{O} \), (B) must be methoxy methane (dimethyl ether, \( \text{CH}_3\text{OCH}_3 \)). Ethers do not have an acidic hydrogen to react with sodium.
3. Compound (A) (ethanol) reacts with ethanoic acid to form a fruity smelling compound (C). This is an esterification reaction. The fruity smelling compound (C) is ethyl ethanoate (an ester).
\[ \text{CH}_3\text{CH}_2\text{OH} + \text{CH}_3\text{COOH} \xrightarrow{\text{conc.H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \]
Therefore:
A = Ethanol (\( \text{CH}_3\text{CH}_2\text{OH} \))
B = Methoxy methane (\( \text{CH}_3\text{OCH}_3 \))
C = Ethyl ethanoate (\( \text{CH}_3\text{COOC}_2\text{H}_5 \))
In simple words: Chemicals A and B have the same number of atoms but are different. A reacts with sodium to make hydrogen gas, which means A is ethanol. B does not react, so B is methoxy methane. A (ethanol) also reacts with ethanoic acid to make a sweet-smelling chemical C, which is ethyl ethanoate.

🎯 Exam Tip: Use characteristic reactions (like reaction with sodium for alcohols, esterification for alcohols and acids) to differentiate between isomers and identify unknown compounds.

Question 2. Write the IUPAC names of the following compounds.

Answer: The table above provides the systematic IUPAC names for the given organic compounds, following the rules for identifying the parent chain, functional groups, and positions of substituents. Each name accurately describes the chemical structure, which is crucial for clear scientific communication. For example, 2-Methyl hexane indicates a hexane chain with a methyl group on the second carbon.
In simple words: This table shows the scientific names for different chemicals based on their structure. For example, a six-carbon chain with a methyl group on the second carbon is called 2-Methyl hexane. These names help us understand exactly what each chemical looks like.

🎯 Exam Tip: Pay close attention to numbering the carbon chain correctly to give the lowest possible numbers to functional groups and substituents.