Is it correct to say: Confusing C_nH_2n (alkene) with C_nH_{2n+2} (alkane)?

Saturated (single bonds only) = 2n+2. One double bond removes 2 H, giving 2n.

Is it correct to say: Drawing structural formulae without showing every bond and H atom?

For SSC full marks, show all C-C and C-H bonds explicitly (or use clear condensed notation).

Is it correct to say: Naming CH_3-CH(OH)-CH_3 as propanol?

It is propan-2-ol (OH on carbon 2). Position number is compulsory in IUPAC names.

Is it correct to say: Saying soap does not work in hard water because 'it dissolves fully'?

Soap actually reacts with Ca^{2+}/Mg^{2+} forming insoluble scum, using up soap needed for cleaning.

Is it correct to say: Writing hydrogenation of ethene without a catalyst?

Nickel catalyst (150 °C) is essential — mention it above the arrow.

Is it correct to say: Writing product of ethanol + Na as ethoxide + H_2O?

Product is sodium ethoxide + H_2 gas, not water. Na reduces H, not O.

Carbon and Its Compounds

Covalent bonding of carbon, hydrocarbons, functional groups, homologous series, soaps/detergents — SSC Science Part 1 Ch 9

📐 11 formulas✏️ 3 examples🎯 6 practice⚖️ 5-6 marks🏫 Maharashtra State Board📚 Class 10✓ 2025–26 syllabus

💡

Board Exam Tips

→Draw structural formulae with all bonds shown — dashes, not lines only. Marks lost for skipping H atoms.
→IUPAC naming of first 4 alkanes, alkenes, alkynes plus alcohols and carboxylic acids is compulsory.
→Marathi terms: संतृप्त (saturated), असंतृप्त (unsaturated), समजातीय श्रेणी (homologous series), प्रकार्यगट (functional group).
→Difference between soap and detergent: soap fails in hard water, detergent works — a 2-mark question.
→Ethanol → ethanoic acid oxidation (with alkaline KMnO_4) is a favourite HOTS.

📐 Formulas(11)

General Formula of Alkanes★ Board fav

C_{n} H_{2 n + 2}

Symbol	Meaning
$n$	Number of carbon atoms (n = 1, 2, 3, ...)

General Formula of Alkenes★ Board fav

C_{n} H_{2 n}

General Formula of Alkynes

C_{n} H_{2 n - 2}

Combustion of Methane

C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O + heat

General Combustion of Alkane

C_{n} H_{2 n + 2} + (\frac{3 n + 1}{2}) O_{2} \to n C O_{2} + (n + 1) H_{2} O

Addition (Hydrogenation)★ Board fav

C H_{2} = C H_{2} + H_{2} Ni C H_{3} - C H_{3}

Substitution (Chlorination of Methane)

C H_{4} + C l_{2} sunlight C H_{3} C l + H C l

Oxidation of Ethanol to Ethanoic Acid

C H_{3} C H_{2} O H alk. KMnO_{4} Δ C H_{3} C O O H

Ester Formation (Esterification)★ Board fav

C H_{3} C O O H + C H_{3} C H_{2} O H conc. H_{2} SO_{4} C H_{3} C O O C_{2} H_{5} + H_{2} O

Saponification (Soap Making)

Fat/Oil + 3 N a O H \to Soap + Glycerol

Reaction of Sodium with Ethanol

2 C H_{3} C H_{2} O H + 2 N a \to 2 C H_{3} C H_{2} O N a + H_{2} ↑

✏️ Solved Examples

1Solved Exampleeasy5 steps

Write the molecular formula and name of the first four members of the alkane series.

General formula CnH_{2n+2}

2Solved Exampleboard3 steps

Explain with equations how ethanol can be converted into (a) ethene, (b) ethanoic acid.

Dehydration with conc. H_2SO_4 at 170 °C

C H_{3} C H_{2} O H 170 ° C conc. H_{2} SO_{4} C H_{2} = C H_{2} + H_{2} O

3Solved ExampleHOTS5 steps

Explain the cleansing action of soap and state why it fails in hard water.

Soap is Na/K salt of long-chain fatty acid — has ionic (hydrophilic) head and hydrocarbon (hydrophobic) tail

⚠️ Traps & Common Mistakes

⚠️Common Mistakes6

1
Confusing C_nH_2n (alkene) with C_nH_{2n+2} (alkane)
✓Saturated (single bonds only) = 2n+2. One double bond removes 2 H, giving 2n.
2
Drawing structural formulae without showing every bond and H atom
✓For SSC full marks, show all C-C and C-H bonds explicitly (or use clear condensed notation).
3
Naming CH_3-CH(OH)-CH_3 as propanol
✓It is propan-2-ol (OH on carbon 2). Position number is compulsory in IUPAC names.
4
Saying soap does not work in hard water because 'it dissolves fully'
✓Soap actually reacts with Ca^{2+}/Mg^{2+} forming insoluble scum, using up soap needed for cleaning.
5
Writing hydrogenation of ethene without a catalyst
✓Nickel catalyst (150 °C) is essential — mention it above the arrow.
6
Writing product of ethanol + Na as ethoxide + H_2O
✓Product is sodium ethoxide + H_2 gas, not water. Na reduces H, not O.

🎯 Practice Yourself

🎯Practice Yourself6 questions

Q1
Write IUPAC names: (a) CH_3-CH_2-CH_2-CHO, (b) CH_3-CH=CH-CH_3.
Q2
Give the molecular formula of butyne and draw its structure.
Q3
Which gas is released when ethanoic acid reacts with sodium carbonate?
Q4
State one physical and one chemical difference between soap and detergent.
Q5
Draw the structural formula of ethyl ethanoate and name the reaction that produces it.
Q6
State one property in which diamond differs from graphite (both are pure carbon).

📝 Notes

Carbon and Its Compounds

Carbon's ability to form four covalent bonds (tetravalency) and chain up with itself (catenation) explains why we have over 10 million carbon compounds. This chapter is the SSC gateway to organic chemistry.

SSC angle

Chapter 9 of Science Part 1 usually contributes 5-6 marks:

1-mark: IUPAC name / structure identification.
3-mark: write reactions of ethanol (or ethene) with catalysts.
HOTS: cleansing action of soap with a labelled micelle diagram.

Why carbon is special

Catenation — self-linking to form long chains, branches and rings.
Tetravalency — four covalent bonds per carbon → huge variety.
Small size — strong C-C and C-H bonds.

Homologous series checklist

Same general formula (C_nH_{2n+2}, etc.).
Successive members differ by -CH_2- (14 u).
Same functional group and similar chemical properties.
Gradual change in physical properties (boiling point, density).

Functional groups to memorise

| Group | Formula | Class | Suffix | |---|---|---|---| | -OH | Hydroxyl | Alcohol | -ol | | -CHO | Aldehyde | Aldehyde | -al | | >C=O | Ketone | Ketone | -one | | -COOH | Carboxylic acid | Acid | -oic acid | | -X | Halo | Haloalkane | halo- | | C=C, C≡C | Double/triple bond | Alkene/Alkyne | -ene/-yne |

Ethanol vs Ethanoic acid — SSC must-know

Ethanol: CH_3CH_2OH — neutral to litmus, denaturant, alcoholic drinks.
Ethanoic acid (vinegar): CH_3COOH — pungent, turns blue litmus red, freezing point 16.6 °C hence 'glacial'.

Soap vs Detergent — one-line SSC answer

Soap = Na salt of long-chain carboxylic acid, fails in hard water. Detergent = Na salt of long-chain sulphonic acid, works even in hard water.

Board vs CBSE

Both boards teach the same organic basics. Maharashtra SSC emphasises structural drawings and comparisons (ethanol vs ethanoic acid, soap vs detergent). Show every C-H bond in structural formulae for full marks.