Class 10 Science · Chapter 4
Short answer:
NCERT Class 10 Science Chapter 4 Carbon and its Compounds me total 13 in-text questions (4 page-wise sets) aur 15 exercise questions hain — sabke detailed solutions yahan Hinglish me diye gaye hain. Chapter cover karta hai: carbon ka covalent bonding (tetravalency + catenation), saturated aur unsaturated hydrocarbons, structural isomerism, functional groups, homologous series, IUPAC nomenclature, carbon compounds ke chemical properties (combustion, oxidation, addition, substitution), do important compounds — ethanol (C2H5OH) aur ethanoic acid (CH3COOH), aur last me soaps, detergents aur micelle ka cleansing action.
Carbon ke paas 4 valence electrons hote hain, isliye wo electron share karta hai — ionic bond nahi banata. Ek atom hone ke bawajood carbon ke 10 million se zyada compounds ban chuke hain, aur uski wajah sirf do properties hain — tetravalency (4 bonds bana sakta hai) aur catenation (carbon-carbon ki lambi chains bana sakta hai). Yahi chapter ka core hai — is ek idea se ismein sab kuch nikalta hai: isomers, homologous series, functional groups, aur ethanol/ethanoic acid ki reactions.
Chapter 4 Summary — 5 Minute Revision
1. Carbon me bonding — covalent bond kyun?
- Carbon ka atomic number 6, electronic configuration 2,4. Outermost shell me 4 electrons.
- Noble gas configuration paane ke liye 4 electrons gain kare ya 4 lose kare — dono impossible hain:
- 4 electrons gain karna: 6 protons ke liye 10 electrons hold karna mushkil hai.
- 4 electrons lose karna: itni zyada energy chahiye ki C4+ banana practically nahi hota.
- Isliye carbon electrons share karta hai — yani covalent bond banata hai.
2. Covalent compounds ke properties
- Melting point aur boiling point kam (intermolecular forces weak hoti hain — bond khud strong hai, par molecules ke beech ka attraction weak).
- Bijli conduct nahi karte — kyunki ions ya free electrons nahi hote.
- Zyadatar water me insoluble, organic solvents me soluble.
3. Carbon ki do superpower properties
- Catenation — carbon apne hi atoms se lambi chain, branched chain aur ring bana leta hai. C–C bond bahut strong hone ki wajah se ye chains stable rehti hain.
- Tetravalency — 4 valence electrons ki wajah se carbon 4 dusre atoms (C, H, O, N, S, Cl) se bond bana sakta hai.
4. Hydrocarbons
| Type | Bond | General formula | Example | Flame |
|---|---|---|---|---|
| Alkane (saturated) | Single C–C | CnH2n+2 | CH4, C2H6 | Clean blue flame |
| Alkene (unsaturated) | Double C=C | CnH2n | C2H4 | Yellow sooty flame |
| Alkyne (unsaturated) | Triple C≡C | CnH2n-2 | C2H2 | Yellow sooty flame |
↔ Table ko side me swipe karein
Cyclic (ring) hydrocarbons bhi hote hain — jaise cyclohexane C6H12, benzene C6H6.
5. Structural isomers
- Same molecular formula, alag structural arrangement = structural isomers.
- Butane C4H10 → 2 isomers. Pentane C5H12 → 3 isomers. Hexane C6H14 → 5 isomers.
- Pehle 3 alkanes (methane, ethane, propane) ke koi structural isomer nahi bante.
6. Functional groups
| Functional group | Formula | Suffix / Prefix | Example |
|---|---|---|---|
| Halo (chloro/bromo) | –Cl, –Br | prefix: chloro-, bromo- | CH3Cl chloromethane |
| Alcohol | –OH | suffix: -ol | C2H5OH ethanol |
| Aldehyde | –CHO | suffix: -al | CH3CHO ethanal |
| Ketone | –CO– | suffix: -one | CH3COCH3 propanone |
| Carboxylic acid | –COOH | suffix: -oic acid | CH3COOH ethanoic acid |
↔ Table ko side me swipe karein
Naming rule: agar suffix vowel (a, e, i, o, u) se shuru ho raha hai, to parent chain ke naam se final 'e' hata do. Jaise propane + -one = propanone (propaneone nahi).
7. Homologous series
- Same functional group wale compounds ki series jisme har member se agla member –CH2 unit se badhta hai.
- Molecular mass ka difference 14 u.
- Chemical properties same, physical properties (m.p., b.p., solubility) gradually change hoti hain.
8. Chemical properties of carbon compounds
(a) Combustion
Saturated hydrocarbon clean blue flame deta hai; unsaturated yellow sooty flame.
CH4 + 2O2 → CO2 + 2H2O + heat & light
(b) Oxidation
Alcohol ko alkaline KMnO4 ya acidified K2Cr2O7 ke saath garam karne par carboxylic acid banta hai. Ye oxidising agents kehlate hain.
CH3CH2OH Alkaline KMnO4 + Heat→ CH3COOH
(c) Addition reaction
Unsaturated compound me nickel/palladium catalyst ki presence me hydrogen add hota hai — isko hydrogenation kehte hain.
C2H4 + H2 Ni→ C2H6
(d) Substitution reaction
Saturated hydrocarbons sunlight me chlorine ke saath substitution dete hain.
CH4 + Cl2 Sunlight→ CH3Cl + HCl
9. Ethanol (C2H5OH)
- Room temperature par liquid, water me har ratio me soluble.
- Sodium ke saath: hydrogen gas nikalti hai (ye alcohol ka test hai).
2Na + 2C2H5OH → 2C2H5ONa + H2↑
- Dehydration: conc. H2SO4 ke saath 443 K par ethene banta hai.
C2H5OH Conc. H2SO4, 443 K→ CH2=CH2 + H2O
Ethanol medicines aur tinctures me solvent hai, par pure ethanol peene se health par serious nuksan hota hai. Methanol to bahut zyada toxic hai — liver me methanal banakar andhapan aur maut tak kar sakta hai.
10. Ethanoic acid (CH3COOH)
- Acetic acid — 5–8% solution ko vinegar kehte hain.
- Pure ethanoic acid 290 K par freeze ho jata hai, isliye ise glacial acetic acid kehte hain.
- Ye ek weak acid hai (mineral acids jaise HCl se weak).
Esterification: acid catalyst ke saath alcohol se ester banta hai — sweet smell.
CH3COOH + C2H5OH Conc. H2SO4→ CH3COOC2H5 + H2O
Saponification: ester + NaOH → alcohol + sodium salt of acid (soap banane ki reaction).
CH3COOC2H5 + NaOH → CH3COONa + C2H5OH
Base ke saath:
CH3COOH + NaOH → CH3COONa + H2O
Carbonate / hydrogencarbonate ke saath: brisk effervescence, CO2 nikalti hai — yahi carboxylic acid ka test hai.
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2↑
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2↑
11. Soaps, detergents aur micelle
- Soap = long chain carboxylic acid ka sodium/potassium salt. Molecule ke do sire hote hain:
- Hydrophilic (ionic –COO–Na+ head) — paani me ghulta hai.
- Hydrophobic (hydrocarbon tail) — oil/grease me ghulta hai.
- Paani me soap molecules ka cluster ban jata hai jisme tail andar oil ki taraf aur head bahar paani ki taraf hoti hai — isko micelle kehte hain.
- Micelle oily dirt ko gher leta hai, agitation se dirt kapde se alag ho jati hai aur paani me emulsion banakar bah jati hai.
- Hard water me Ca2+ aur Mg2+ ions hote hain jo soap ke saath insoluble salt (scum) bana dete hain — jhaag nahi banta aur soap waste hota hai.
- Detergents ammonium/sulphonate salts hote hain — inke calcium/magnesium salts bhi soluble rehte hain, isliye hard water me bhi jhaag dete hain.
In-Text Questions — Solutions
Q1. What would be the electron dot structure of carbon dioxide which has the formula CO2?
CO2 me carbon ke paas 4 valence electrons hain aur har oxygen ke paas 6. Carbon apne 4 electrons ko do oxygen atoms ke saath share karta hai — har oxygen ke saath 2 electron pairs, yani double bond.
O = C = O
Electron dot form me: carbon ke aur har oxygen ke beech do shared electron pairs (4 dots) dikhaye jaate hain, aur har oxygen atom par 2 lone pairs (4 dots) bache rehte hain. Is tarah carbon ke paas 8 electrons ho jaate hain aur har oxygen ke paas bhi 8 — dono ka octet pura.
Q2. What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur? (Hint: The eight atoms of sulphur are joined together in the form of a ring.)
Sulphur ka electronic configuration 2,8,6 hai — yani har S atom ke paas 6 valence electrons. Octet pura karne ke liye har sulphur atom ko sirf 2 aur electrons chahiye.
S8 me aath sulphur atoms ek ring (crown shape) me jude hote hain. Har sulphur apne dono padosi sulphur atoms ke saath ek-ek single covalent bond banata hai (1 shared pair har bond me), aur uske paas 2 lone pairs (4 dots) bache rehte hain.
S–S–S–S–S–S–S–S (aath atoms ka closed ring)
Total 8 single S–S bonds. Har atom: 2 bonding pairs + 2 lone pairs = 8 electrons = octet complete.
Q3. How many structural isomers can you draw for pentane?
Pentane ka formula C5H12 hai aur iske 3 structural isomers bante hain:
- n-Pentane — straight chain: CH3–CH2–CH2–CH2–CH3
- Iso-pentane (2-methylbutane) — 4 carbon ki chain, doosre carbon par ek CH3 branch.
- Neo-pentane (2,2-dimethylpropane) — 3 carbon ki chain, beech wale carbon par do CH3 branch.
Teeno ka molecular formula same C5H12 hai, sirf carbon skeleton ka arrangement alag hai.
Q4. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Do properties hain:
- Catenation — carbon apne hi doosre carbon atoms ke saath bond banakar lambi chains, branched chains aur rings bana leta hai. C–C bond bahut strong hone ki wajah se ye structures stable rehte hain. Koi aur element itni lambi stable chains nahi bana pata.
- Tetravalency — carbon ke paas 4 valence electrons hain, isliye wo 4 dusre atoms (carbon, hydrogen, oxygen, nitrogen, sulphur, halogens) ke saath covalent bond bana sakta hai. Isse bahut zyada combinations possible ho jaate hain.
Q5. What will be the formula and electron dot structure of cyclopentane?
Cyclopentane ek cyclic saturated hydrocarbon hai jisme 5 carbon ek ring me jude hain. Ring wale saturated hydrocarbon ka general formula CnH2n hota hai, to n = 5 par:
Formula = C5H10
Structure: paanch carbon atoms ek closed pentagon ring banate hain. Har carbon apne do padosi carbons ke saath ek-ek single bond banata hai aur bache do bonds se do hydrogen atoms jodta hai.
Electron dot me: har C–C aur har C–H bond ek shared electron pair (do dots) se dikhaya jaata hai. Har carbon ke paas kul 4 shared pairs = 8 electrons, octet complete. Koi lone pair nahi.
Q6. Draw the structures for the following compounds. (i) Ethanoic acid (ii) Bromopentane (iii) Butanone (iv) Hexanal. Are structural isomers possible for bromopentane?
(i) Ethanoic acid — CH3COOH
Do carbon; doosre carbon par –COOH group (C ka O ke saath double bond aur –OH group).
CH3 – COOH
(ii) Bromopentane — C5H11Br
Paanch carbon ki chain, ek hydrogen ki jagah –Br.
CH3 – CH2 – CH2 – CH2 – CH2Br (1-bromopentane)
Haan, structural isomers possible hain. Straight chain me hi Br ki position badalne se teen isomer milte hain — 1-bromopentane, 2-bromopentane aur 3-bromopentane (aur branched chain lene par aur bhi bante hain).
(iii) Butanone — CH3COCH2CH3
Chaar carbon, doosre carbon par ketone (>C=O) group.
CH3 – CO – CH2 – CH3
(iv) Hexanal — CH3CH2CH2CH2CH2CHO
Chhe carbon, chain ke ek sire par aldehyde (–CHO) group.
CH3 – CH2 – CH2 – CH2 – CH2 – CHO
Q7. How would you name the following compounds? (i) CH3—CH2—Br (ii) HCHO (methanal-type aldehyde with one carbon) (iii) H—C≡C—CH2—CH2—CH2—CH3
(i) CH3—CH2—Br → Bromoethane
Do carbon = eth-, saturated = -ane, aur halogen prefix ke roop me = bromo. Isliye bromoethane.
(ii) HCHO → Methanal
Ek carbon = meth-, aldehyde group –CHO ka suffix = -al. 'Methane' se final 'e' hata kar methanal.
(iii) H—C≡C—CH2—CH2—CH2—CH3 → Hexyne (Hex-1-yne)
Chhe carbon = hex-, triple bond hai = -yne. Triple bond pehle carbon par hai, isliye hex-1-yne.
Q8. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Jab ethanol ko alkaline KMnO4 ya acidified K2Cr2O7 ke saath garam karte hain to ethanoic acid banta hai:
CH3CH2OH Alkaline KMnO4 + Heat→ CH3COOH
Is reaction me ethanol (C2H6O) me oxygen add hota hai aur hydrogen remove hota hai. Kisi compound me oxygen ka addition ya hydrogen ka removal — dono hi oxidation kehlate hain. Isliye ye ek oxidation reaction hai.
Yahan KMnO4 / K2Cr2O7 oxidising agent ka kaam karte hain.
Q9. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Ethyne (C2H2) ek unsaturated hydrocarbon hai. Air me oxygen sirf lagbhag 21% hota hai, isliye air ke saath jalane par incomplete combustion hoti hai — yellow sooty flame banti hai aur temperature kam rehta hai. Sath hi kaajal (carbon soot) nikalta hai.
Pure oxygen ke saath jalane par complete combustion hoti hai aur bahut hi high temperature ki clean blue flame (oxy-acetylene flame) milti hai, jo metals ko pighla kar weld karne ke liye zaroori hai.
2C2H2 + 5O2 → 4CO2 + 2H2O + heat
Isliye welding me ethyne + air nahi, balki ethyne + oxygen ka mixture use hota hai.
Q10. How would you distinguish experimentally between an alcohol and a carboxylic acid?
Do simple tests hain:
(a) Sodium carbonate / sodium hydrogencarbonate test (best test):
Dono ko alag-alag test tube me NaHCO3 ya Na2CO3 solution ke saath milaiye.
- Carboxylic acid — brisk effervescence (fizzing) deta hai, CO2 gas nikalti hai jo lime water ko doodhiya kar deti hai.
- Alcohol — koi reaction nahi, koi gas nahi.
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2↑
(b) Litmus test:
Carboxylic acid blue litmus ko red kar deta hai; alcohol litmus par koi asar nahi karta (wo neutral hai).
Q11. What are oxidising agents?
Wo substances jo doosre substances ko oxygen dete hain ya unse hydrogen chheenn lete hain — yani doosre ko oxidise karte hain aur khud reduce ho jaate hain — unhe oxidising agents kehte hain.
Common examples: alkaline potassium permanganate (KMnO4), acidified potassium dichromate (K2Cr2O7).
CH3CH2OH Alkaline KMnO4 + Heat→ CH3COOH
Yahan KMnO4 ethanol ko oxygen deta hai, isliye wo oxidising agent hai.
Q12. Would you be able to check if water is hard by using a detergent?
Nahi. Detergents se hard water check nahi kiya ja sakta.
Detergents ammonium ya sulphonate salts hote hain aur inke calcium aur magnesium salts bhi paani me soluble rehte hain. Isliye detergent hard water aur soft water — dono me achhi tarah jhaag (lather) deta hai aur koi farak nahi dikhta.
Hard water test karne ke liye soap use karte hain: soft water me soap achha jhaag deta hai, jabki hard water me jhaag ke bajaye scum (safed insoluble parat) banta hai.
Q13. People use a variety of methods to wash clothes. Usually after adding the soap, they beat the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
Soap ke molecules ka hydrophobic (tail) end oily dirt me ghus jata hai aur hydrophilic (head) end paani ki taraf rehta hai — is tarah dirt ke charon taraf micelle ban jata hai.
Lekin ye micelle-me-fansi hui dirt abhi bhi kapde ke fabric se chipki hui rehti hai. Use fabric se alag karne ke liye mechanical energy chahiye.
Beating, scrubbing ya washing machine me agitation se wahi mechanical force milta hai, jisse dirt kapde se ukhad kar paani me emulsion ke roop me suspend ho jati hai aur paani ke saath bah jaati hai. Isliye agitation zaroori hai.
Poore Class 10 Science ke handwritten colour notes
IITian & district toppers ke banaye short notes — revision-ready, diagram ke saath. Board se pehle poora syllabus 3 din me revise.
Exercise Questions — Solutions (Q1–Q15)
Q1. Ethane, with the molecular formula C2H6 has (a) 6 covalent bonds (b) 7 covalent bonds (c) 8 covalent bonds (d) 9 covalent bonds.
Answer: (b) 7 covalent bonds
Ethane me 1 C–C bond aur 6 C–H bonds hote hain (har carbon 3 hydrogen se juda hai). Total = 1 + 6 = 7 covalent bonds.
Q2. Butanone is a four-carbon compound with the functional group (a) carboxylic acid (b) aldehyde (c) ketone (d) alcohol.
Answer: (c) ketone
Naam ke ant me suffix '-one' ketone group (>C=O, chain ke beech me) ko darshata hai. Butanone ka structure CH3–CO–CH2–CH3 hai.
Q3. While cooking, if the bottom of the vessel is getting blackened on the outside, it means that (a) the food is not cooked completely (b) the fuel is not burning completely (c) the fuel is wet (d) the fuel is burning completely.
Answer: (b) the fuel is not burning completely
Oxygen ki supply kam hone par fuel ki incomplete combustion hoti hai, jisse unburnt carbon particles (soot / kaajal) nikalte hain aur bartan ka bottom kaala pad jata hai. Gas burner ke air holes band ho jaayen to yahi hota hai — unhe saaf karne se flame phir se blue ho jati hai.
Q4. Explain the nature of the covalent bond using the bond formation in CH3Cl.
Carbon ke paas 4 valence electrons hain, hydrogen ke paas 1 aur chlorine ke paas 7.
CH3Cl me carbon apne 4 electrons me se:
- 3 electrons teen hydrogen atoms ke saath share karta hai → 3 C–H single covalent bonds. Har hydrogen ka duplet (2 electrons) pura ho jata hai.
- 1 electron chlorine ke saath share karta hai → 1 C–Cl single covalent bond. Chlorine ka octet (8 electrons) pura ho jata hai.
H – C(H)(H) – Cl (4 single covalent bonds)
Nature: ismein koi electron transfer nahi hota, sirf sharing hoti hai — isliye ye covalent bond hai. Har shared pair dono atoms ke nucleus ko attract karta hai, jisse strong bond banta hai. Kyunki koi ion nahi banta, CH3Cl bijli conduct nahi karta aur uska melting/boiling point kam hota hai.
Q5. Draw the electron dot structures for (a) ethanoic acid (b) H2S (c) propanone (d) F2.
(a) Ethanoic acid, CH3COOH
Pehla carbon 3 hydrogen se 3 single bonds banata hai aur doosre carbon se 1 single bond. Doosra carbon ek oxygen se double bond (2 shared pairs) aur doosre oxygen se single bond banata hai; us oxygen se ek hydrogen juda hota hai. Double bond wale O par 2 lone pairs, –OH wale O par 2 lone pairs.
CH3 – C(=O) – O – H
(b) H2S
Sulphur (2,8,6) ke paas 6 valence electrons. Wo do hydrogen ke saath 2 single bonds (2 shared pairs) banata hai aur uske paas 2 lone pairs bachte hain.
H – S – H (S par 2 lone pairs)
(c) Propanone, CH3COCH3
Beech wala carbon oxygen ke saath double bond banata hai aur dono taraf ke CH3 groups se ek-ek single bond. Oxygen par 2 lone pairs.
CH3 – C(=O) – CH3
(d) F2
Fluorine (2,7) ke paas 7 valence electrons. Do fluorine atoms ek electron pair share karke single bond banate hain; har F par 3 lone pairs bachte hain.
F – F (har F par 3 lone pairs)
Q6. What is a homologous series? Explain with an example.
Homologous series aise carbon compounds ki series hai jisme sabhi members me same functional group hota hai aur har member apne pichle member se –CH2 unit se badhta hai.
Characteristics:
- Consecutive members ke molecular mass ka difference 14 u hota hai.
- Sabhi members ke chemical properties same hoti hain (kyunki functional group same hai).
- Physical properties (melting point, boiling point, solubility) molecular mass badhne ke saath gradually change hoti hain.
- Sabhi ko ek general formula se represent kiya ja sakta hai.
Example — alkane series (general formula CnH2n+2):
| Compound | Formula | Molecular mass (u) |
|---|---|---|
| Methane | CH4 | 16 |
| Ethane | C2H6 | 30 |
| Propane | C3H8 | 44 |
| Butane | C4H10 | 58 |
↔ Table ko side me swipe karein
Dekhiye — har baar difference 14 u ka hai.
Q7. How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Physical properties:
| Property | Ethanol (C2H5OH) | Ethanoic acid (CH3COOH) |
|---|---|---|
| Smell | Pleasant smell | Vinegar jaisi teekhi (pungent) smell |
| Melting point | 156 K | 290 K — winter me jam jata hai (glacial acetic acid) |
| Boiling point | 351 K | 391 K |
↔ Table ko side me swipe karein
Chemical properties:
| Test | Ethanol | Ethanoic acid |
|---|---|---|
| Litmus test | Koi asar nahi (neutral) | Blue litmus ko red kar deta hai |
| NaHCO3 / Na2CO3 | Koi reaction nahi | Brisk effervescence, CO2 gas |
| Sodium metal | H2 gas nikalti hai | H2 gas nikalti hai (dono dete hain, isliye ye distinguishing test nahi) |
↔ Table ko side me swipe karein
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2↑
Best test: sodium hydrogencarbonate test — sirf ethanoic acid effervescence deta hai.
Q8. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Soap molecule ke do alag-alag sire hote hain:
- Ionic head (–COO–Na+) — hydrophilic, paani me ghulta hai.
- Long hydrocarbon tail — hydrophobic, paani me nahi ghulta par oil/grease me ghulta hai.
Jab soap paani me daala jata hai to hydrocarbon tail paani se door bhagti hai, isliye soap molecules aise cluster bana lete hain jisme tails andar ki taraf (oil ki taraf) aur ionic heads bahar paani ki taraf hoti hain. Isi spherical cluster ko micelle kehte hain.
Ethanol me micelle nahi banega. Ethanol ek organic solvent hai jisme soap ki hydrocarbon tail aasani se ghul jaati hai. Jab tail solvent se bhaagne ki koshish nahi karti, to cluster banane ki koi zarurat hi nahi rehti — isliye micelle formation nahi hota.
Q9. Why are carbon and its compounds used as fuels for most applications?
Kyunki carbon aur uske compounds jalne par bahut zyada heat aur light dete hain. Inki reasons:
- Inka calorific value high hota hai — thodi si quantity se kaafi energy milti hai.
- Oxygen ki paryapt supply me ye completely burn hote hain aur sirf CO2 aur H2O dete hain — smoke ya residue nahi bachta.
- Ye aasani se available hain (coal, petroleum, natural gas, LPG, CNG) aur handle/store karna aasan hai.
- Ignition temperature theek hoti hai — na itni kam ki khud aag pakad le, na itni zyada ki jalana mushkil ho.
CH4 + 2O2 → CO2 + 2H2O + heat & light
Q10. Explain the formation of scum when hard water is treated with soap.
Hard water me calcium (Ca2+) aur magnesium (Mg2+) ions ke salts ghule hote hain.
Soap sodium ya potassium ka salt hota hai — long chain carboxylic acid ka. Jab soap hard water me daala jata hai, to soap ke anions in Ca2+/Mg2+ ions ke saath reaction karke calcium aur magnesium ke insoluble salts bana lete hain.
2C17H35COONa + CaCl2 → (C17H35COO)2Ca↓ + 2NaCl
Ye insoluble white precipitate paani ki surface par safed chipchipi parat ki tarah jam jata hai — isi ko scum kehte hain.
Iski wajah se soap jhaag (lather) nahi de pata aur kaafi soap bekaar chala jata hai — kapde saaf karne ke liye zyada soap lagana padta hai.
Q11. What change will you observe if you test soap with litmus paper (red and blue)?
Soap ek strong base (NaOH/KOH) aur ek weak carboxylic acid ka salt hai. Paani me ghulne par ye hydrolysis ki wajah se basic (alkaline) solution deta hai.
- Red litmus paper → blue ho jayega.
- Blue litmus paper → blue hi rahega (koi change nahi).
Yahi wajah hai ki soap solution ki pH 7 se zyada hoti hai aur haath par chikna/slippery lagta hai.
Q12. What is hydrogenation? What is its industrial application?
Hydrogenation wo addition reaction hai jisme unsaturated hydrocarbon me nickel ya palladium catalyst ki presence me hydrogen add kiya jata hai, jisse wo saturated ban jata hai.
CH2=CH2 + H2 Ni catalyst→ CH3–CH3
Industrial application: vegetable oils ko vanaspati ghee me badalne ke liye. Vegetable oils me unsaturated (double bond wali) long chains hoti hain aur wo liquid hote hain. Nickel catalyst ke saath hydrogen pass karne par ye saturated ho jaate hain aur room temperature par solid fat ban jaate hain.
Note: health ke liye unsaturated (vegetable) oils behtar mane jaate hain; saturated fats zyada khana sehat ke liye achha nahi hota.
Q13. Which of the following hydrocarbons undergo addition reactions: C2H6, C3H8, C3H6, C2H2 and CH4.
Addition reaction sirf unsaturated hydrocarbons (jinme double ya triple bond hai) dete hain.
| Compound | Type | Addition reaction? |
|---|---|---|
| C2H6 (ethane) | Saturated, CnH2n+2 | Nahi |
| C3H8 (propane) | Saturated | Nahi |
| C3H6 (propene) | Unsaturated, CnH2n | Haan |
| C2H2 (ethyne) | Unsaturated, CnH2n-2 | Haan |
| CH4 (methane) | Saturated | Nahi |
↔ Table ko side me swipe karein
Answer: C3H6 aur C2H2 addition reactions dete hain. Baaki teen saturated hain, wo substitution reaction dete hain.
Q14. Give a test that can be used to differentiate chemically between butter and cooking oil.
Butter me mukhya roop se saturated fats hote hain, jabki cooking oil me unsaturated fats. Unsaturation test se dono ko alag kiya ja sakta hai.
Test 1 — Bromine water test: dono ke sample me alag-alag bromine water ki kuch boondein daaliye.
- Cooking oil — bromine water ka orange/brown colour hat jata hai (decolourise ho jata hai), kyunki double bond par bromine add ho jata hai.
- Butter — colour waisa hi rehta hai (saturated hone ki wajah se addition nahi hoti).
Test 2 — Alkaline KMnO4 test: cooking oil alkaline potassium permanganate ka purple colour decolourise kar deta hai; butter nahi karta.
Q15. Explain the mechanism of the cleaning action of soaps.
Kapdon par lagi zyadatar dirt oil ya grease me fansi hoti hai, aur oil paani me ghulta nahi — isliye sirf paani se dirt nahi nikalti. Soap ka kaam yahin shuru hota hai.
Step 1 — Soap ka structure: soap molecule ke do sire hote hain — ek hydrophobic hydrocarbon tail (oil me ghulne wali) aur ek hydrophilic ionic head –COO–Na+ (paani me ghulne wali).
Step 2 — Micelle formation: paani me daalte hi soap molecules ki tails oily dirt ke andar ghus jaati hain aur ionic heads bahar paani ki taraf rehti hain. Is tarah oil drop ke charon or ek spherical cluster ban jata hai — micelle.
Step 3 — Agitation: beating, scrubbing ya washing machine ki agitation se micelle-me-fansi dirt kapde se ukhad kar paani me aa jaati hai.
Step 4 — Emulsion aur rinsing: micelles ki bahar wali ionic heads ek doosre ko repel karti hain, isliye oil drops dobara aapas me nahi judte aur paani me emulsion ke roop me suspend rehte hain. Saaf paani se rinse karte hi ye sab dirt bah jaati hai aur kapda saaf ho jata hai.
Important Equations — Ek Nazar Me
| Concept / Compound | Formula / Reaction | Yaad rakhne ki baat |
|---|---|---|
| Alkane (saturated) | CnH2n+2 | Sirf single bonds, substitution reaction |
| Alkene | CnH2n | Ek double bond, addition reaction |
| Alkyne | CnH2n-2 | Ek triple bond, addition reaction |
| Cyclic saturated (ring) | CnH2n | Cyclopentane C5H10, cyclohexane C6H12 |
| Homologous series difference | –CH2, mass difference 14 u | Chemical properties same rehti hain |
| Combustion of methane | CH4 + 2O2 → CO2 + 2H2O | Clean blue flame |
| Oxidation of ethanol | CH3CH2OH Alk. KMnO4, Δ→ CH3COOH | Oxygen add, hydrogen remove |
| Hydrogenation | C2H4 + H2 Ni→ C2H6 | Oil → vanaspati ghee |
| Substitution (chlorination) | CH4 + Cl2 Sunlight→ CH3Cl + HCl | Saturated hydrocarbons ki reaction |
| Ethanol + Sodium | 2Na + 2C2H5OH → 2C2H5ONa + H2↑ | Sodium ethoxide + hydrogen gas |
| Dehydration of ethanol | C2H5OH Conc. H2SO4, 443 K→ C2H4 + H2O | H2SO4 = dehydrating agent |
| Esterification | CH3COOH + C2H5OH Conc. H2SO4→ CH3COOC2H5 + H2O | Sweet smell wala ester |
| Saponification | CH3COOC2H5 + NaOH → CH3COONa + C2H5OH | Soap banane ki reaction |
| Acid + Base | CH3COOH + NaOH → CH3COONa + H2O | Neutralisation |
| Acid + Carbonate | 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2↑ | Brisk effervescence — acid ka test |
| Acid + Hydrogencarbonate | CH3COOH + NaHCO3 → CH3COONa + H2O + CO2↑ | Alcohol vs acid distinguish karne ka test |
| Scum formation | 2C17H35COONa + CaCl2 → (C17H35COO)2Ca↓ + 2NaCl | Hard water me jhaag nahi banta |
| Glacial acetic acid | Pure CH3COOH, freezes at 290 K | Winter me jam jata hai |
↔ Table ko side me swipe karein
Common Mistakes — Yahan Marks Kat te Hain
- Ethane ke bonds ginne me galti. Students sirf C–H bonds gin lete hain aur beech wala C–C bond bhool jaate hain — jawab 6 likh dete hain. Sahi jawab 7 hai (1 C–C + 6 C–H). Hamesha carbon skeleton pehle banao, phir hydrogen jodo.
- Nomenclature me final 'e' nahi hatana. Jab suffix vowel se shuru ho (-ol, -al, -one, -oic acid), tab parent chain ka last 'e' hatta hai. Propane + one = propanone, 'propaneone' nahi. Lekin halogen prefix (chloro-, bromo-) me kuch nahi hatta — 'chloroethane' sahi hai.
- Sodium metal test se alcohol aur acid distinguish karna. Ye galat hai — ethanol aur ethanoic acid dono sodium ke saath H2 gas dete hain. Distinguishing test hamesha NaHCO3/Na2CO3 hai (sirf acid effervescence deta hai) ya litmus test.
- Reaction conditions likhna bhool jaana. Arrow ke upar catalyst/temperature nahi likhne par marks kat jaate hain. Hydrogenation me Ni, esterification me conc. H2SO4, dehydration me conc. H2SO4 + 443 K, substitution me sunlight, oxidation me alkaline KMnO4 + heat — ye zaroori hain.
- Hard water test ke liye detergent bata dena. Detergent hard aur soft dono paani me jhaag deta hai, isliye usse hardness detect nahi hoti. Hardness sirf soap se check hoti hai — hard water me scum banta hai, jhaag nahi.
- Isomers me same structure do baar likh dena. Pentane ke 3 isomers puchhe jaane par students chain ko mod kar (bend karke) chautha 'isomer' bana dete hain — par sirf mod dene se structure nahi badalta. Isomer tabhi alag hai jab carbon skeleton ka connection pattern alag ho. Pentane = 3, butane = 2, hexane = 5.
Board-Style Important Questions
- 1 mark: Kisi ek property ka naam batao jiski wajah se carbon bahut saare compounds bana pata hai, aur usko ek line me define karo.
- 1 mark: Pure ethanoic acid ko 'glacial acetic acid' kyun kehte hain?
- 2 marks: Ethanol aur ethanoic acid ko chemically distinguish karne ka ek test likho, uski reaction ke saath.
- 3 marks: Hydrogenation kya hai? Uski reaction likho aur ek industrial application batao.
- 3 marks: Homologous series kya hai? Uske teen characteristics likho aur alkane series ka example do.
- 5 marks: (a) Soap ka cleansing action micelle formation ki madad se samjhao. (b) Hard water me soap jhaag kyun nahi deta? Reaction likho. (c) Detergent hard water me kaam kyun kar leta hai?
Quick Quiz — Score Check Karein
Q1. Carbon covalent bonds kyun banata hai, ionic bonds kyun nahi?
Q2. Carbon compounds itni badi sankhya (10 million+) me kis wajah se milte hain?
Q3. Covalent compounds (jaise carbon compounds) ka ek typical property kya hai?
Q4. Ethene (C2H4) kis series ka hydrocarbon hai aur uska general formula kya hai?
Q5. Butane (C4H10) ke kitne structural isomers bante hain?
Q6. Propanone (CH3COCH3) me '-one' suffix se pehle 'propane' ka final 'e' kyun hataya gaya?
Q7. Homologous series ke consecutive members ke molecular mass me kitna difference hota hai?
Q8. CH4 + Cl2 → CH3Cl + HCl (sunlight me) — yeh reaction kis type ki hai?
Q9. Ethanol ko alkaline KMnO4 ya acidified K2Cr2O7 ke saath garam karne par kya banta hai, aur yeh kaunsi reaction hai?
Q10. Pure ethanoic acid ko 'glacial acetic acid' kyun kehte hain?
Aksar Poochhe Jaane Wale Sawaal
Carbon ionic bond kyun nahi banata?
Carbon ke paas 4 valence electrons hain. 4 electrons gain karke C4- banane ke liye 6 protons ko 10 electrons hold karne padenge, jo mushkil hai. 4 electrons lose karke C4+ banane ke liye bahut zyada energy chahiye. Dono raste practical nahi hain, isliye carbon electrons share karta hai — yani covalent bond banata hai.
Saturated aur unsaturated hydrocarbon me sabse aasan farak kya hai?
Saturated me sirf single C-C bonds hote hain (alkane, CnH2n+2) aur wo clean blue flame ke saath jalte hain, substitution reaction dete hain. Unsaturated me double ya triple bond hota hai (alkene CnH2n, alkyne CnH2n-2), wo yellow sooty flame dete hain aur addition reaction dete hain. Lab me test: unsaturated compound bromine water ka colour hata deta hai, saturated nahi.
Isomers kaise gine jaate hain — koi trick hai?
Pehle sabse lambi straight chain banao, wo ek isomer. Phir chain ek carbon chhoti karo aur bacha hua CH3 group alag-alag positions par lagao (chain ke end wale carbon par mat lagao, kyunki wo wahi straight chain ban jayegi). Aise hi aage badho. Methane, ethane aur propane ke koi isomer nahi hote. Butane = 2, pentane = 3, hexane = 5.
Ethanol aur methanol me kya farak hai?
Ethanol C2H5OH hai — do carbon wala alcohol, medicines aur tinctures me solvent ke roop me use hota hai. Methanol CH3OH hai — ek carbon wala aur bahut zyada toxic. Methanol liver me oxidise hokar methanal banata hai jo cells ko damage karta hai, jisse andhapan aur maut tak ho sakti hai. Isliye industrial spirit me methanol milaya jaata hai — usko denatured spirit kehte hain taaki koi pi na sake.
Micelle exactly kya hota hai?
Micelle soap molecules ka ek spherical cluster hai jo paani me banta hai. Iske andar ki taraf sabhi hydrocarbon tails hoti hain jo oily dirt ko pakad leti hain, aur bahar ki taraf ionic heads hoti hain jo paani me ghuli rehti hain. Isi wajah se oil, jo paani me ghulta hi nahi, micelle ke andar fans kar paani ke saath bah jaata hai.
Esterification aur saponification me kya farak hai?
Esterification me carboxylic acid aur alcohol conc. H2SO4 ki presence me milkar sweet smell wala ester aur paani banate hain. Saponification uska ulta hai — ester ko sodium hydroxide ke saath garam karne par wapas alcohol aur carboxylic acid ka sodium salt milta hai, aur wahi sodium salt hi soap hai. Isliye saponification ko soap banane ki reaction kehte hain.
Class 10 Science — Saare Chapters
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Class 10 Science ke saare chapters ke colour handwritten short notes — diagrams, formulas aur important points ek jagah.
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