Carbon and Its Compounds
Combustion, Oxidation, Addition and Substitution Reactions
दहन, ऑक्सीकरण, योग एवं प्रतिस्थापन अभिक्रियाएँ
Class 10 Science | CBSE + Foundation + Competitive
Carbon and Its Compounds | Chemical Reactions
1. Chemical Properties of Carbon Compounds – रासायनिक गुण
English:
Carbon compounds undergo different chemical reactions depending upon their structure, functional group and type of carbon-carbon bond. The four important reactions studied in Class 10 are:
कार्बन यौगिक अपनी संरचना, क्रियात्मक समूह तथा कार्बन-कार्बन बंध के प्रकार के आधार पर विभिन्न रासायनिक अभिक्रियाएँ करते हैं। कक्षा 10 में मुख्य रूप से चार अभिक्रियाएँ महत्वपूर्ण हैं:
Carbon compounds undergo different chemical reactions depending upon their structure, functional group and type of carbon-carbon bond. The four important reactions studied in Class 10 are:
- Combustion Reaction
- Oxidation Reaction
- Addition Reaction
- Substitution Reaction
कार्बन यौगिक अपनी संरचना, क्रियात्मक समूह तथा कार्बन-कार्बन बंध के प्रकार के आधार पर विभिन्न रासायनिक अभिक्रियाएँ करते हैं। कक्षा 10 में मुख्य रूप से चार अभिक्रियाएँ महत्वपूर्ण हैं:
- दहन अभिक्रिया
- ऑक्सीकरण अभिक्रिया
- योग अभिक्रिया
- प्रतिस्थापन अभिक्रिया
Memory Trick – याद रखने की ट्रिक:
🔥 C = Combustion
🧪 O = Oxidation
➕ A = Addition
🔄 S = Substitution
C → O → A → S
🔥 C = Combustion
🧪 O = Oxidation
➕ A = Addition
🔄 S = Substitution
C → O → A → S
2. Combustion Reaction – दहन अभिक्रिया
English:
Combustion is a chemical reaction in which a carbon compound reacts with oxygen and produces heat and usually light. Most carbon compounds burn in oxygen to form carbon dioxide, water and heat.
हिन्दी:
दहन वह रासायनिक अभिक्रिया है जिसमें कार्बन यौगिक ऑक्सीजन के साथ अभिक्रिया करके कार्बन डाइऑक्साइड, जल तथा ऊष्मा उत्पन्न करता है।
Combustion is a chemical reaction in which a carbon compound reacts with oxygen and produces heat and usually light. Most carbon compounds burn in oxygen to form carbon dioxide, water and heat.
हिन्दी:
दहन वह रासायनिक अभिक्रिया है जिसमें कार्बन यौगिक ऑक्सीजन के साथ अभिक्रिया करके कार्बन डाइऑक्साइड, जल तथा ऊष्मा उत्पन्न करता है।
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Example: Combustion of Methane
मीथेन ऑक्सीजन में जलकर कार्बन डाइऑक्साइड और जल बनाता है।
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
मीथेन ऑक्सीजन में जलकर कार्बन डाइऑक्साइड और जल बनाता है।
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Combustion of Ethanol – एथेनॉल का दहन:
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O + Heat
Important:
Many carbon compounds are used as fuels because their combustion releases a large amount of heat.
महत्वपूर्ण:
कई कार्बन यौगिक ईंधन के रूप में उपयोग किए जाते हैं क्योंकि उनके दहन से काफी मात्रा में ऊष्मा प्राप्त होती है।
Many carbon compounds are used as fuels because their combustion releases a large amount of heat.
महत्वपूर्ण:
कई कार्बन यौगिक ईंधन के रूप में उपयोग किए जाते हैं क्योंकि उनके दहन से काफी मात्रा में ऊष्मा प्राप्त होती है।
3. Incomplete Combustion – अपूर्ण दहन
English:
When sufficient oxygen is not available, carbon compounds may undergo incomplete combustion. It may produce carbon monoxide (CO) and/or carbon (soot) instead of only carbon dioxide.
हिन्दी:
जब पर्याप्त ऑक्सीजन उपलब्ध नहीं होती है तब कार्बन यौगिकों का अपूर्ण दहन हो सकता है। इसमें कार्बन डाइऑक्साइड के साथ या उसके स्थान पर कार्बन मोनोऑक्साइड तथा कार्बन (कालिख) बन सकता है।
When sufficient oxygen is not available, carbon compounds may undergo incomplete combustion. It may produce carbon monoxide (CO) and/or carbon (soot) instead of only carbon dioxide.
हिन्दी:
जब पर्याप्त ऑक्सीजन उपलब्ध नहीं होती है तब कार्बन यौगिकों का अपूर्ण दहन हो सकता है। इसमें कार्बन डाइऑक्साइड के साथ या उसके स्थान पर कार्बन मोनोऑक्साइड तथा कार्बन (कालिख) बन सकता है।
2CH₄ + 3O₂ → 2CO + 4H₂O
CH₄ + O₂ → C + 2H₂O
Safety Point:
Carbon monoxide (CO) is a poisonous gas.
कार्बन मोनोऑक्साइड एक विषैली गैस है।
कार्बन मोनोऑक्साइड एक विषैली गैस है।
4. Oxidation Reaction – ऑक्सीकरण अभिक्रिया
English:
Oxidation can be understood as addition of oxygen or removal of hydrogen from a substance. In carbon compounds, ethanol can be oxidised to ethanoic acid.
हिन्दी:
ऑक्सीकरण को किसी पदार्थ में ऑक्सीजन के जुड़ने या हाइड्रोजन के हटने की प्रक्रिया के रूप में समझा जा सकता है। कार्बन यौगिकों में एथेनॉल का ऑक्सीकरण करके एथेनोइक अम्ल प्राप्त किया जा सकता है।
Oxidation can be understood as addition of oxygen or removal of hydrogen from a substance. In carbon compounds, ethanol can be oxidised to ethanoic acid.
हिन्दी:
ऑक्सीकरण को किसी पदार्थ में ऑक्सीजन के जुड़ने या हाइड्रोजन के हटने की प्रक्रिया के रूप में समझा जा सकता है। कार्बन यौगिकों में एथेनॉल का ऑक्सीकरण करके एथेनोइक अम्ल प्राप्त किया जा सकता है।
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
Ethanol
→ Oxidation
→ Ethanoic Acid
एथेनॉल → ऑक्सीकरण → एथेनोइक अम्ल
एथेनॉल → ऑक्सीकरण → एथेनोइक अम्ल
Oxidising Agents – ऑक्सीकारक:
- Alkaline potassium permanganate – KMnO₄
- Acidified potassium dichromate – K₂Cr₂O₇
Exam Point:
KMnO₄ और K₂Cr₂O₇ का उपयोग कार्बनिक यौगिकों के ऑक्सीकरण के लिए किया जा सकता है।
KMnO₄ और K₂Cr₂O₇ का उपयोग कार्बनिक यौगिकों के ऑक्सीकरण के लिए किया जा सकता है।
5. Addition Reaction – योग अभिक्रिया
English:
Addition reactions are generally shown by unsaturated carbon compounds containing double or triple bonds. In this reaction, atoms or groups are added across a multiple bond.
हिन्दी:
योग अभिक्रिया सामान्यतः उन असंतृप्त कार्बन यौगिकों में होती है जिनमें द्विबंध या त्रिबंध उपस्थित होता है। इस अभिक्रिया में बहु-बंध पर परमाणु या समूह जुड़ते हैं।
Addition reactions are generally shown by unsaturated carbon compounds containing double or triple bonds. In this reaction, atoms or groups are added across a multiple bond.
हिन्दी:
योग अभिक्रिया सामान्यतः उन असंतृप्त कार्बन यौगिकों में होती है जिनमें द्विबंध या त्रिबंध उपस्थित होता है। इस अभिक्रिया में बहु-बंध पर परमाणु या समूह जुड़ते हैं।
CH₂=CH₂ + H₂ → CH₃–CH₃
Ethene + Hydrogen → Ethane
एथीन + हाइड्रोजन → एथेन
यह एक addition reaction है क्योंकि एथीन के C=C बंध पर हाइड्रोजन जुड़ता है।
एथीन + हाइड्रोजन → एथेन
यह एक addition reaction है क्योंकि एथीन के C=C बंध पर हाइड्रोजन जुड़ता है।
6. Hydrogenation – हाइड्रोजनीकरण
Hydrogenation is the addition of hydrogen to an unsaturated
compound in the presence of a catalyst.
असंतृप्त यौगिक में उत्प्रेरक की उपस्थिति में हाइड्रोजन जोड़ने की प्रक्रिया को हाइड्रोजनीकरण कहते हैं।
असंतृप्त यौगिक में उत्प्रेरक की उपस्थिति में हाइड्रोजन जोड़ने की प्रक्रिया को हाइड्रोजनीकरण कहते हैं।
CH₂=CH₂ + H₂
Ni
→
CH₃–CH₃
Catalyst – उत्प्रेरक:
Nickel (Ni)
Example:
Vegetable oils → Hydrogenation → More saturated products
वनस्पति तेल → हाइड्रोजनीकरण → अधिक संतृप्त उत्पाद
Nickel (Ni)
Example:
Vegetable oils → Hydrogenation → More saturated products
वनस्पति तेल → हाइड्रोजनीकरण → अधिक संतृप्त उत्पाद
Industrial Application:
Hydrogenation is used in the processing of vegetable oils to produce more saturated products such as vanaspati.
Hydrogenation is used in the processing of vegetable oils to produce more saturated products such as vanaspati.
7. Substitution Reaction – प्रतिस्थापन अभिक्रिया
English:
Substitution reaction is a reaction in which one atom or group of atoms in a molecule is replaced by another atom or group. Saturated hydrocarbons commonly undergo substitution reactions.
हिन्दी:
प्रतिस्थापन अभिक्रिया वह अभिक्रिया है जिसमें किसी अणु का एक परमाणु या परमाणुओं का समूह दूसरे परमाणु या समूह द्वारा प्रतिस्थापित हो जाता है। संतृप्त हाइड्रोकार्बन सामान्यतः प्रतिस्थापन अभिक्रियाएँ करते हैं।
Substitution reaction is a reaction in which one atom or group of atoms in a molecule is replaced by another atom or group. Saturated hydrocarbons commonly undergo substitution reactions.
हिन्दी:
प्रतिस्थापन अभिक्रिया वह अभिक्रिया है जिसमें किसी अणु का एक परमाणु या परमाणुओं का समूह दूसरे परमाणु या समूह द्वारा प्रतिस्थापित हो जाता है। संतृप्त हाइड्रोकार्बन सामान्यतः प्रतिस्थापन अभिक्रियाएँ करते हैं।
CH₄ + Cl₂
Sunlight
→
CH₃Cl + HCl
Explanation – व्याख्या:
मीथेन में उपस्थित एक हाइड्रोजन परमाणु को क्लोरीन परमाणु प्रतिस्थापित कर देता है।
इसलिए यह substitution reaction है।
मीथेन में उपस्थित एक हाइड्रोजन परमाणु को क्लोरीन परमाणु प्रतिस्थापित कर देता है।
इसलिए यह substitution reaction है।
8. Chlorination of Methane – मीथेन का क्लोरीनीकरण
Methane reacts with chlorine in the presence of sunlight
or ultraviolet light.
मीथेन सूर्य के प्रकाश या UV प्रकाश की उपस्थिति में क्लोरीन के साथ अभिक्रिया करता है।
मीथेन सूर्य के प्रकाश या UV प्रकाश की उपस्थिति में क्लोरीन के साथ अभिक्रिया करता है।
CH₄ + Cl₂ → CH₃Cl + HCl
Further substitution can occur:
CH₃Cl + Cl₂ → CH₂Cl₂ + HCl
CH₂Cl₂ + Cl₂ → CHCl₃ + HCl
CHCl₃ + Cl₂ → CCl₄ + HCl
CH₃Cl + Cl₂ → CH₂Cl₂ + HCl
CH₂Cl₂ + Cl₂ → CHCl₃ + HCl
CHCl₃ + Cl₂ → CCl₄ + HCl
Remember:
Methane + Chlorine + Sunlight → Substitution Reaction
Methane + Chlorine + Sunlight → Substitution Reaction
9. Addition vs Substitution – योग एवं प्रतिस्थापन में अंतर
| Basis | Addition Reaction | Substitution Reaction |
|---|---|---|
| Usually occurs in | Unsaturated compounds | Saturated compounds |
| Bond | Double/Triple bond | Single bonds |
| Process | Atoms/groups are added | One atom/group replaces another |
| Example | Ethene + H₂ → Ethane | Methane + Cl₂ → CH₃Cl + HCl |
10. Reaction Summary – अभिक्रियाओं का सार
| Reaction | Reactant | Product |
|---|---|---|
| Combustion | Carbon compound + O₂ | CO₂ + H₂O + Heat |
| Oxidation | Ethanol + [O] | Ethanoic acid |
| Addition | Ethene + H₂ | Ethane |
| Substitution | Methane + Cl₂ | Chloromethane + HCl |
11. 30 MCQs – बहुविकल्पीय प्रश्न
Q1. Complete combustion of methane produces:
A) CO + H₂O
B) CO₂ + H₂O
C) C + H₂
D) CH₃Cl
Answer: B) CO₂ + H₂O
Q2. Which reaction is characteristic of unsaturated compounds?
A) Addition
B) Substitution
C) Neutralisation
D) Precipitation
Answer: A) Addition
Q3. Ethanol on oxidation gives:
A) Ethane
B) Methane
C) Ethanoic acid
D) Ethene
Answer: C) Ethanoic acid
Q4. Nickel is used as a catalyst in:
A) Combustion
B) Substitution
C) Neutralisation
D) Hydrogenation
Answer: D) Hydrogenation
Q5. Methane reacts with chlorine in the presence of:
A) Sunlight
B) Water
C) NaOH
D) CO₂
Answer: A) Sunlight
Q6. Which compound contains a double bond?
A) Methane
B) Ethene
C) Ethane
D) Propane
Answer: B) Ethene
Q7. The formula of ethene is:
A) C₂H₆
B) C₂H₂
C) C₂H₄
D) CH₄
Answer: C) C₂H₄
Q8. Which is a poisonous gas produced during incomplete combustion?
A) O₂
B) N₂
C) CO₂
D) CO
Answer: D) CO
Q9. Hydrogenation converts an unsaturated compound into a:
A) More saturated compound
B) More ionic compound
C) Metal
D) Salt
Answer: A) More saturated compound
Q10. Which reaction occurs in methane chlorination?
A) Addition
B) Substitution
C) Oxidation only
D) Neutralisation
Answer: B) Substitution
Q11. Which substance is an oxidising agent?
A) KMnO₄
B) NaCl
C) CH₄
D) H₂
Answer: A) KMnO₄
Q12. Ethene + H₂ gives:
A) Ethanol
B) Ethanoic acid
C) Ethane
D) Methane
Answer: C) Ethane
Q13. Saturated hydrocarbons generally undergo:
A) Addition
B) Substitution
C) Hydrolysis
D) Neutralisation
Answer: B) Substitution
Q14. Which gas is formed during complete combustion?
A) CO₂
B) CO
C) H₂
D) N₂
Answer: A) CO₂
Q15. Oxidation of ethanol produces:
A) Ethyne
B) Methane
C) Ethanoic acid
D) Ethane
Answer: C) Ethanoic acid
Q16. Which catalyst is commonly used in hydrogenation?
A) Cu
B) Fe
C) Zn
D) Ni
Answer: D) Ni
Q17. A reaction involving addition across C=C is:
A) Addition
B) Substitution
C) Neutralisation
D) Decomposition
Answer: A) Addition
Q18. Methane is:
A) Unsaturated
B) Saturated
C) Aromatic only
D) Ionic
Answer: B) Saturated
Q19. Which reaction releases heat?
A) Combustion
B) Addition only
C) Substitution only
D) Hydrolysis only
Answer: A) Combustion
Q20. The product of CH₄ + Cl₂ in sunlight is:
A) C₂H₆
B) CH₃Cl + HCl
C) CO₂
D) CH₃OH
Answer: B) CH₃Cl + HCl
Q21. Incomplete combustion may produce:
A) Only oxygen
B) Only nitrogen
C) Carbon monoxide
D) Hydrogen chloride only
Answer: C) Carbon monoxide
Q22. Which compound is unsaturated?
A) C₂H₄
B) C₂H₆
C) CH₄
D) C₃H₈
Answer: A) C₂H₄
Q23. Hydrogenation requires:
A) Chlorine
B) Hydrogen
C) Oxygen only
D) Nitrogen
Answer: B) Hydrogen
Q24. Which one is an oxidising agent?
A) KMnO₄
B) CH₄
C) C₂H₆
D) H₂
Answer: A) KMnO₄
Q25. Substitution means:
A) Addition of oxygen
B) Removal of carbon
C) Replacement of an atom/group
D) Formation of water only
Answer: C) Replacement of an atom/group
Q26. Which reaction is used in processing vegetable oils?
A) Hydrogenation
B) Neutralisation
C) Precipitation
D) Electrolysis
Answer: A) Hydrogenation
Q27. Which compound is saturated?
A) Ethene
B) Ethyne
C) Ethane
D) Propene
Answer: C) Ethane
Q28. What is required for chlorination of methane?
A) Sunlight/UV light
B) Nickel only
C) Water only
D) NaCl only
Answer: A) Sunlight/UV light
Q29. Ethanol is oxidised to:
A) Ethane
B) Ethanoic acid
C) Methane
D) Ethyne
Answer: B) Ethanoic acid
Q30. Which sequence is correct?
A) Unsaturated → Addition
B) Saturated → Addition only
C) Ethanol → Methane by oxidation
D) Methane + Cl₂ → Addition
Answer: A) Unsaturated → Addition
12. 30 Subjective Questions – वर्णनात्मक प्रश्न
1 Mark
Q1. What is combustion?
दहन क्या है?
दहन क्या है?
Answer:
Combustion is the reaction of a substance with oxygen producing
heat and usually light.
ऑक्सीजन के साथ अभिक्रिया जिसमें ऊष्मा तथा सामान्यतः प्रकाश उत्पन्न होता है, दहन कहलाती है।
ऑक्सीजन के साथ अभिक्रिया जिसमें ऊष्मा तथा सामान्यतः प्रकाश उत्पन्न होता है, दहन कहलाती है।
1 Mark
Q2. Name the gas formed during complete combustion of carbon compounds.
Answer: Carbon dioxide (CO₂).
1 Mark
Q3. Name the catalyst used in hydrogenation.
Answer: Nickel (Ni).
1 Mark
Q4. Which reaction is characteristic of unsaturated compounds?
Answer: Addition reaction.
1 Mark
Q5. What is the product of oxidation of ethanol?
Answer: Ethanoic acid.
2 Marks
Q6. Write the combustion equation of methane.
Solution:
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
2 Marks
Q7. What is an addition reaction?
Answer:
An addition reaction is a reaction in which atoms or groups are added across a multiple bond.
Example: CH₂=CH₂ + H₂ → CH₃CH₃
An addition reaction is a reaction in which atoms or groups are added across a multiple bond.
Example: CH₂=CH₂ + H₂ → CH₃CH₃
2 Marks
Q8. What is substitution reaction?
Answer:
A reaction in which one atom or group is replaced by another atom or group is called substitution reaction.
CH₄ + Cl₂ → CH₃Cl + HCl
A reaction in which one atom or group is replaced by another atom or group is called substitution reaction.
CH₄ + Cl₂ → CH₃Cl + HCl
2 Marks
Q9. What is hydrogenation?
Answer:
Addition of hydrogen to an unsaturated compound in the presence of a catalyst is called hydrogenation.
Addition of hydrogen to an unsaturated compound in the presence of a catalyst is called hydrogenation.
2 Marks
Q10. What happens during incomplete combustion?
Answer:
When oxygen is insufficient, carbon compounds may undergo incomplete combustion and form CO and/or carbon.
When oxygen is insufficient, carbon compounds may undergo incomplete combustion and form CO and/or carbon.
3 Marks
Q11. Explain combustion of carbon compounds with an example.
Answer:
- Carbon compounds react with oxygen.
- Heat and usually light are produced.
- Complete combustion generally gives CO₂ and H₂O.
3 Marks
Q12. Explain oxidation of ethanol.
Answer:
Ethanol is oxidised using an oxidising agent such as KMnO₄ or K₂Cr₂O₇.
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
Thus ethanol changes into ethanoic acid.
Ethanol is oxidised using an oxidising agent such as KMnO₄ or K₂Cr₂O₇.
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
Thus ethanol changes into ethanoic acid.
3 Marks
Q13. Explain addition reaction with an example.
Answer:
Unsaturated compounds containing double or triple bonds undergo addition reactions.
CH₂=CH₂ + H₂ → CH₃CH₃
Ethene changes into ethane.
Unsaturated compounds containing double or triple bonds undergo addition reactions.
CH₂=CH₂ + H₂ → CH₃CH₃
Ethene changes into ethane.
3 Marks
Q14. Explain substitution reaction of methane.
Answer:
Methane reacts with chlorine in the presence of sunlight.
CH₄ + Cl₂ → CH₃Cl + HCl
One hydrogen atom of methane is replaced by chlorine.
Methane reacts with chlorine in the presence of sunlight.
CH₄ + Cl₂ → CH₃Cl + HCl
One hydrogen atom of methane is replaced by chlorine.
3 Marks
Q15. Why is nickel used in hydrogenation?
Answer:
Nickel acts as a catalyst. It helps hydrogen add to the multiple bond of an unsaturated compound and increases the rate of reaction.
Nickel acts as a catalyst. It helps hydrogen add to the multiple bond of an unsaturated compound and increases the rate of reaction.
4 Marks
Q16. Differentiate between addition and substitution reactions.
| Addition | Substitution |
|---|---|
| Usually unsaturated compounds | Usually saturated compounds |
| Atoms/groups are added | One atom/group replaces another |
| Example: Ethene + H₂ | Example: Methane + Cl₂ |
4 Marks
Q17. Explain complete and incomplete combustion.
Complete combustion:
Occurs in sufficient oxygen and generally produces CO₂, H₂O and heat.
Incomplete combustion:
Occurs when oxygen is insufficient and may produce CO and/or carbon.
Occurs in sufficient oxygen and generally produces CO₂, H₂O and heat.
Incomplete combustion:
Occurs when oxygen is insufficient and may produce CO and/or carbon.
4 Marks
Q18. Write four major chemical reactions of carbon compounds.
- Combustion
- Oxidation
- Addition
- Substitution
4 Marks
Q19. Explain hydrogenation of vegetable oils.
Answer:
Vegetable oils contain unsaturated compounds. Hydrogen is added to their multiple bonds in the presence of nickel catalyst. This increases saturation and is used in the processing of vegetable oils.
Vegetable oils contain unsaturated compounds. Hydrogen is added to their multiple bonds in the presence of nickel catalyst. This increases saturation and is used in the processing of vegetable oils.
4 Marks
Q20. Write the chemical equation for chlorination of methane
and explain it.
CH₄ + Cl₂
Sunlight
→ CH₃Cl + HCl
One hydrogen atom of methane is replaced by chlorine. Therefore, it is a substitution reaction.
One hydrogen atom of methane is replaced by chlorine. Therefore, it is a substitution reaction.
5 Marks
Q21. Explain the four major chemical properties of
carbon compounds with equations.
1. Combustion:
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
2. Oxidation:
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
3. Addition:
CH₂=CH₂ + H₂ → CH₃CH₃
4. Substitution:
CH₄ + Cl₂ → CH₃Cl + HCl
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
2. Oxidation:
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
3. Addition:
CH₂=CH₂ + H₂ → CH₃CH₃
4. Substitution:
CH₄ + Cl₂ → CH₃Cl + HCl
5 Marks
Q22. Explain why carbon compounds are used as fuels.
Many carbon compounds undergo combustion and release
considerable heat energy.
For example: CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Therefore hydrocarbons and several other carbon compounds are widely used as fuels.
For example: CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Therefore hydrocarbons and several other carbon compounds are widely used as fuels.
5 Marks
Q23. Explain the oxidation of ethanol in detail.
Ethanol reacts with an oxidising agent such as alkaline
KMnO₄ or acidified K₂Cr₂O₇.
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
The alcohol group is converted into the carboxylic acid functional group, producing ethanoic acid.
CH₃CH₂OH + 2[O] → CH₃COOH + H₂O
The alcohol group is converted into the carboxylic acid functional group, producing ethanoic acid.
5 Marks
Q24. Explain the addition reaction of ethene with hydrogen.
Ethene contains a carbon-carbon double bond.
Hydrogen adds across this double bond in the presence
of nickel catalyst.
CH₂=CH₂ + H₂ Ni → CH₃–CH₃
Ethene is converted into ethane.
CH₂=CH₂ + H₂ Ni → CH₃–CH₃
Ethene is converted into ethane.
5 Marks
Q25. Explain substitution reaction with methane as an example.
Methane is a saturated hydrocarbon.
In the presence of sunlight/UV light, chlorine replaces
hydrogen atoms of methane.
CH₄ + Cl₂ → CH₃Cl + HCl
Further substitution can produce CH₂Cl₂, CHCl₃ and CCl₄.
CH₄ + Cl₂ → CH₃Cl + HCl
Further substitution can produce CH₂Cl₂, CHCl₃ and CCl₄.
6 Marks
Q26. Describe combustion and incomplete combustion
of carbon compounds.
Complete Combustion:
When sufficient oxygen is available, carbon compounds burn completely.
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Incomplete Combustion:
When oxygen is insufficient, incomplete combustion occurs.
2CH₄ + 3O₂ → 2CO + 4H₂O
It may also produce carbon/soot.
When sufficient oxygen is available, carbon compounds burn completely.
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Incomplete Combustion:
When oxygen is insufficient, incomplete combustion occurs.
2CH₄ + 3O₂ → 2CO + 4H₂O
It may also produce carbon/soot.
6 Marks
Q27. Explain addition and hydrogenation reactions
with suitable examples.
Unsaturated compounds undergo addition reactions.
CH₂=CH₂ + H₂ → CH₃CH₃
The addition of hydrogen to an unsaturated compound in the presence of nickel catalyst is called hydrogenation.
Hydrogenation is used in the processing of vegetable oils to make more saturated products.
CH₂=CH₂ + H₂ → CH₃CH₃
The addition of hydrogen to an unsaturated compound in the presence of nickel catalyst is called hydrogenation.
Hydrogenation is used in the processing of vegetable oils to make more saturated products.
6 Marks
Q28. Explain the chlorination of methane step by step.
Methane reacts with chlorine in sunlight.
Step 1: CH₄ + Cl₂ → CH₃Cl + HCl
Step 2: CH₃Cl + Cl₂ → CH₂Cl₂ + HCl
Step 3: CH₂Cl₂ + Cl₂ → CHCl₃ + HCl
Step 4: CHCl₃ + Cl₂ → CCl₄ + HCl
This is a substitution reaction.
Step 1: CH₄ + Cl₂ → CH₃Cl + HCl
Step 2: CH₃Cl + Cl₂ → CH₂Cl₂ + HCl
Step 3: CH₂Cl₂ + Cl₂ → CHCl₃ + HCl
Step 4: CHCl₃ + Cl₂ → CCl₄ + HCl
This is a substitution reaction.
6 Marks
Q29. Compare combustion, oxidation, addition and
substitution reactions.
| Reaction | Main Feature | Example |
|---|---|---|
| Combustion | Reaction with oxygen | CH₄ + O₂ |
| Oxidation | Addition of oxygen/removal of hydrogen | Ethanol → Ethanoic acid |
| Addition | Addition across multiple bond | Ethene + H₂ → Ethane |
| Substitution | Replacement of atom/group | Methane + Cl₂ |
6 Marks
Q30. Prepare a complete reaction map of carbon compounds.
CARBON COMPOUNDS
↓
🔥 COMBUSTION
Carbon compound + O₂
↓
CO₂ + H₂O + Heat
↓
🧪 OXIDATION
Ethanol
↓
Ethanoic Acid
↓
➕ ADDITION
Ethene + H₂
↓
Ethane
↓
🔄 SUBSTITUTION
Methane + Cl₂
↓
Chloromethane + HCl
↓
🔥 COMBUSTION
Carbon compound + O₂
↓
CO₂ + H₂O + Heat
↓
🧪 OXIDATION
Ethanol
↓
Ethanoic Acid
↓
➕ ADDITION
Ethene + H₂
↓
Ethane
↓
🔄 SUBSTITUTION
Methane + Cl₂
↓
Chloromethane + HCl
13. Quick Revision – त्वरित पुनरावृत्ति
- Combustion: Carbon compound + O₂ → CO₂ + H₂O + Heat
- Incomplete Combustion: CO and/or carbon may be formed.
- Oxidation: Ethanol → Ethanoic acid
- Addition: Usually occurs in unsaturated compounds.
- Hydrogenation: Addition of H₂ to an unsaturated compound.
- Catalyst: Nickel (Ni)
- Substitution: Usually occurs in saturated hydrocarbons.
- Methane Chlorination: CH₄ + Cl₂ → CH₃Cl + HCl
⭐ ONE-LINE EXAM REVISION
🔥 Combustion: Carbon compound + O₂ → CO₂ + H₂O + Heat
🧪 Oxidation: Ethanol → Ethanoic Acid
➕ Addition: Unsaturated + H₂ → Saturated
🔄 Substitution: CH₄ + Cl₂ → CH₃Cl + HCl
Remember:
Unsaturated → Addition
Saturated → Substitution
🔥 Combustion: Carbon compound + O₂ → CO₂ + H₂O + Heat
🧪 Oxidation: Ethanol → Ethanoic Acid
➕ Addition: Unsaturated + H₂ → Saturated
🔄 Substitution: CH₄ + Cl₂ → CH₃Cl + HCl
Remember:
Unsaturated → Addition
Saturated → Substitution
