10th Science - Book Back Answers - Chemistry Unit 11 - English Medium Guides

 

SSLC / 10th - Science - Book Back Answers - Chemistry Unit 11 - English Medium

Tamil Nadu Board 10th Standard  Science - Chemistry Unit 11: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 11 – Chemistry from the Tamil Nadu State Board 10th Standard  Science textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Chemistry Unit 11along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 10 students! Prepare well and aim for top scores. Thank you!

Topic: Carbon and its Compounds

I. Choose the correct Answer

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 Key:
(b) alkene
 
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 Key:
(d) Alcohol
 
3. The secondary suffix used in IUPAC nomenclature of an aldehyde is:
(a) – ol
(b) – oic acid
(c) – al
(d) – one
Answer Key:
(c) – al
 
4. Which of the following pairs can be the successive members of a homologous series?
(a) C₃H₈ and C₄H₁₀
(b) C₂H₂ and C₂H₄
(c) CH₄ and C₃H₆
(d) C₂H₅OH and C₄H₈OH.
Answer Key:
(a) C₃H₈ and C₄H₁₀

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 Key:
(b) Combustion of ethanol
 
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 Key:
(a) 95.5 %
 
7. Which of the following are used as anaesthetics?
(a) Carboxylic acids
(b) Ethers
(c) Esters
(d) Aldehydes
Answer Key:
(b) Ethers
 
8. TFM in soaps represents _____ content in soap.
(a) mineral
(b) vitamin
(c) fatty acid
(d) carbohydrate.
Answer Key:
(c) fatty acid

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 – SO₃ ^–Na⁺
(d) It is effective even in hard water.
Answer Key:
(a) It is a sodium salt of long-chain fatty acids

II. Fill in the blanks

1. An atom or a group of atoms which is responsible for chemical characteristics of an organic compound is called …………
2. The general molecular formula of alkynes is ………..
3. In IUPAC name, the carbon skeleton of a compound is represented by ………. (root word / prefix / suffix)
4. (Saturated / Unsaturated) ……….. compounds decolourize bromine water.
5. Dehydration of ethanol by cone. Sulphuric acid forms ………. (ethene/ ethane)
6. 100 % pure ethanol is called ………..
7. Ethanoic acid turns ………… litmus to …………
8. The alkaline hydrolysis of fatty acids is termed as …………
9. Biodegradable detergents are made of …………. (branched / straight) chain hydrocarbons.
Answer Key:
1. Functional group
2- C_nH_2n-2
3. root word
4. unsaturated
5. ethene
6. absolute alcohol
7. Blue, red
8. Saponification
9. straight

 

III. Match the following

1. Match the Column I and Column II.

Column I		Column II.
1	Functional group –OH	i	Benzene
2	Heterocyclic	ii	Potassium stearate
3	Unsaturated	iii	Alcohol
4	Soap	iv	Furan
5	Carbocyclic	v	Ethene

Answer Key:

Column I		Column II.
1	Functional group –OH	iii	Alcohol
2	Heterocyclic	iv	Furan
3	Unsaturated	v	Ethene
4	Soap	ii	Potassium stearate
5	Carbocyclic	i	Benzene

a

IV.  Assertion & Reason 

Answer the following questions using the data given below:
i) A and R are correct, R explains the A.
ii) A is correct, R is wrong.
iii) A is wrong, R is correct.
iv) A and R are correct, R doesn’t explains A.

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 Key:
(a) Assertion and Reason are correct, Reason explains the Assertion.

2. Assertion: Alkanes are saturated hydrocrabons.
Reason: Hydrocarbons consits of covalnet bonds.
(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 Key:
(d) Assertion and Reason are correct, Reason doesn’t explains Assertion.

V.  Short answer questions

1. Name the simplest ketone and give its structural formula.
Answer Key:
The simplest ketone is Propanone.
It’s structural formula:

 
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 Key:

 

3. How is ethanoic acid prepared from ethanol? Give the chemical equation.
Answer Key:
Ethanol is oxidized to ethanoic acid with alkaline KMnO₄ or acidified K₂Cr₂O₇.
 $\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{H}\underset{\mathbf{2}\mathbf{O}}{\overset{{\mathbf{K}}_{\mathbf{2}}\mathbf{C}{\mathbf{r}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{7}}\mathbf{/}{\mathbf{H}}^{\mathbf{+}}}{\mathbf{\to }}}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{H}\mathbf{ }\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$

                                                   Ethanoic acid
4. How do detergents cause water pollution? Suggest remedial measures to prevent this pollution?
Answer Key:
• Some detergents having a branched hydrocarbon chain are not fully biodegradable by microorganisms present in water. So, they cause water pollution.
• They have straight hydrocarbon chains, in biodegradable detergents, which can be easily degraded by bacteria.

5. Differentiate soaps and detergents.
Answer Key:

soaps	detergents.
It is a sodium salt of long chain fatty acids.	It is a sodium salt of sulphonic acids.
The iconic part of a soap is – COO –Na+	The iconic part of a detergent is – SO3 –Na+
It is prepared from animal fats or vegetables oils.	It is prepared from hydrocarbons obtained from crude oil.
It is effectiveness is reduced when used in hard water.	It is effective even in hard water.
It forms a scum in hard water.	Does not form a scum in hard water.
It has poor foaming capacity.	It has rich foaming capacity.
Soaps are biodegradable .	Most of the detergents are non-biodegradable.

 

 

VI. Long answer question

1. What is called a homologous series? Give any three of its characteristics?
Answer Key:
A homologous series is a group or a class of organic compounds having the same general formula and similar chemical properties in which the successive members differ by a – CH₂ group.
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.
• Chemical properties of the members of a homologous series are similar.
 
2. Arrive at, systematically, the IUPAC name of the compound: CH₃-CH₂– CH₂-OH.
Answer Key:
Step 1: The parent chain consists of 3 carbon atoms. The root word is ‘Prop’.
Step 2: There are single bonds between the carbon atoms of the chain. So, the primary suffix is ‘ane’.
Step 3: Since, the compound contains – OH group, it is an alcohol. The carbon chain is numbered from the end which is closest to – OH group. (Rule 3)
$\stackrel{\mathbf{3}}{\mathbf{C}}{\mathbf{H}}_{\mathbf{3}}\mathbf{-}\stackrel{\mathbf{2}}{\mathbf{C}}{\mathbf{H}}_{\mathbf{2}}\mathbf{-}\stackrel{\mathbf{1}}{\mathbf{C}}{\mathbf{H}}_{\mathbf{1}}\mathbf{-}\mathbf{O}\mathbf{H}$
Step 4: The locant number of – OH group is l and thus the secondary suffix is ‘l-ol’.
The name of the compound is Prop + ane + (l – ol) = Propan-l-ol
 
3. How is ethanol manufactured from sugarcane?
Answer Key:
Ethanol is manufactured in industries by the fermentation of molasses, which is a by-product obtained during the manufacture of sugar from sugarcane. Molasses is a dark coloured syrupy liquid left after the crystallization of sugar from the concentrated sugarcane juice. Molasses contain about 30% of sucrose, which cannot be separated by crystallization. It is converted into ethanol by the following steps:
(i) Dilution of molasses: Molasses is first diluted with water to bring down the concentration of sugar to about 8 to 10 percent.
(ii) Addition of Nitrogen source: Molasses usually contains enough nitrogenous matter to act as food for yeast during the fermentation process. If the nitrogen content of the molasses is poor, it may be fortified by the addition of ammonium sulphate or ammonium phosphate.
(iii) Addition of Yeastr The solution obtained in step (ii) is collected in large ‘fermentation tanks’ and yeast is added to it. The mixture is kept at about 303K for a few days. During this period, the enzymes invertase and zymase present in yeast, bring about the conversion of sucrose into ethanol.
${\mathbf{C}}_{\mathbf{12}}{\mathbf{H}}_{\mathbf{22}}{\mathbf{O}}_{\mathbf{11}}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\stackrel{\mathbf{i}\mathbf{n}\mathbf{v}\mathbf{e}\mathbf{r}\mathbf{t}\mathbf{a}\mathbf{s}\mathbf{e}}{\mathbf{\to }}{\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}\mathbf{+}{\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}$

Sugar                                         Glucose     Fructose

${\mathbf{ \; \; \; C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}\stackrel{\mathbf{Z}\mathbf{y}\mathbf{m}\mathbf{a}\mathbf{s}\mathbf{e}}{\to }{\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{O}\mathbf{H}\mathbf{+}\mathbf{2}\mathbf{C}{\mathbf{O}}_{\mathbf{2}}$

    glucose or fructose           ethanol
The fermented liquid is technically called wash.
(iv) Distillation of ‘Wash’: The fermented liquid (i.e., wash), containing 15 to 18 percent alcohol, is now subjected to fractional distillation. The main fraction drawn is an aqueous solution of ethanol which contains 95.5% of ethanol and 4.5% of water. This is called rectified spirit. This mixture is then refluxed over quicklime for about 5 to 6 hours and then allowed to stand for 12 hours. On distillation of this mixture, pure alcohol (100%) is obtained. This is called absolute alcohol.
 
4.Give the balanced chemical equation of the following reactions:
(i) Neutralization of NaOH with ethanoic acid.
Answer Key:
$\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{H}\mathbf{+}\mathbf{N}\mathbf{a}\mathbf{O}\mathbf{H}\mathbf{\to }\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{N}\mathbf{a}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$
                                          Sodium           water

                                          ethanoate

(ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO3.
Answer Key:
$\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{H}\mathbf{+}\mathbf{N}\mathbf{a}\mathbf{H}\mathbf{C}{\mathbf{O}}_{\mathbf{3}}\mathbf{\to }\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{N}\mathbf{a}\mathbf{+}\mathbf{C}{\mathbf{O}}_{\mathbf{2}}\mathbf{\uparrow }\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$
Ethanoic        Sodium           Sodium           Corbani

acid               bycorbonate   ethanoate        dioxide

(iii) Oxidation of ethanol by acidified potassium dichromate.
Answer Key:
$\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{H}\mathbf{+}\mathbf{2}\mathbf{\left[}\mathbf{O}\mathbf{\right]}\stackrel{{\mathbf{H}}^{\mathbf{+}}\mathbf{/}{\mathbf{K}}_{\mathbf{2}}\mathbf{C}{\mathbf{r}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{7}}}{\mathbf{\to }}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{H}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$
  Ethanol                                           Ethanoic acid

(iv) Combustion of ethanol.
Answer Key:
${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{O}\mathbf{H}\mathbf{+}\mathbf{3}{\mathbf{O}}_{\mathbf{2}}\mathbf{\to }\mathbf{2}\mathbf{C}{\mathbf{O}}_{\mathbf{2}}\mathbf{\uparrow }\mathbf{+}\mathbf{3}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$
 Ethanol                  Corbani Oxide   Water

 

5.Explain the mechanism of cleansing action of soap.
Answer Key:
A soap molecule contains two chemically distinct parts that interact differently with water. It has one polar end, which is a short head with a carboxylate group (-COONa) and one non – polar end having the long tail made of the hydrocarbon chain.
The polar end is hydrophilic (Water-loving) in nature and this end is attracted towards the water. The non – polar end is hydrophobic (Water hating) in nature and it is attracted towards dirt or oil on the cloth, but not attracted towards the water. Thus, the hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the entire molecule soluble in water.
When soap or detergent is dissolved in water, the molecules join together as clusters called ‘micelles’. Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar end of the soap molecules. The charged carboxylate end of the soap molecules makes the micelles soluble in water. Thus, the dirt is washed away with the soap.

.

VII. HOT questions

1. The molecular formula of an alcohol is C₄H₁₀O. The locant number of its -OH group is 2.
(i) Draw its structural formula.
Answer Key:
 $\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{-}\underset{\stackrel{\mathbf{|}}{\mathbf{O}\mathbf{H}}}{\mathbf{C}\mathbf{H}}\mathbf{-}\mathbf{C}{\mathbf{H}}_{\mathbf{2}}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}$
(ii) Give its IUPAC name.
Answer Key:
Butan-2-ol
(iii) Is it saturated or unsaturated?
Answer Key:
Saturated

2. An organic compound ‘A’ is widely used as a preservative and has the molecular formula C₂ H₄ O₂ . This compound reacts with ethanol to form a sweet smelling compound ‘B’.
(i) Identify the compound ‘A’.
Answer Key:
Organic Compound ‘A’ with the molecules formula C₂ H₄ O₂ which is a preservative is acetic acid (or) ethanoic acid.
A – CH₃COOH
(ii) Write the chemical equation for its reaction with ethanol to form compound ‘B’.
Answer Key:
$\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}\mathbf{H}\mathbf{+}{\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{O}\mathbf{H}\stackrel{\mathbf{c}\mathbf{o}\mathbf{n}{\mathbf{H}}_{\mathbf{2}}\mathbf{S}{\mathbf{O}}_{\mathbf{4}}}{\mathbf{\to }}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{O}\mathbf{O}{\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$
 Ethanoic             Ethanol                                     Ethyl ethanoate

 Acide

B – Ethyl ethanoate (ester – sweet smelling)
(iii) Name the process.
Answer Key:
Esterification