Class 10 Chemistry: Carbon

Cheatsheet Content

### Versatile Nature of Carbon - **Tetravalency:** Carbon has 4 valence electrons, forming 4 covalent bonds. - **Catenation:** Carbon atoms can link with other carbon atoms to form long chains, branched chains, or rings. This property gives rise to a large number of carbon compounds. - **Multiple Bonds:** Carbon can form single, double, and triple bonds with other carbon atoms and with other elements (e.g., C=C, C≡C, C=O, C≡N). ### Hydrocarbons - **Definition:** Compounds containing only carbon and hydrogen. - **Saturated Hydrocarbons (Alkanes):** - Single bonds between C atoms (C-C). - General formula: $C_nH_{2n+2}$ - Examples: Methane ($CH_4$), Ethane ($C_2H_6$), Propane ($C_3H_8$). - **Unsaturated Hydrocarbons:** - **Alkenes:** Contains at least one C=C double bond. - General formula: $C_nH_{2n}$ - Examples: Ethene ($C_2H_4$), Propene ($C_3H_6$). - **Alkynes:** Contains at least one C≡C triple bond. - General formula: $C_nH_{2n-2}$ - Examples: Ethyne ($C_2H_2$), Propyne ($C_3H_4$). ### Functional Groups - **Definition:** An atom or group of atoms responsible for the characteristic chemical properties of an organic compound. - **Common Functional Groups:** - **Haloalkanes:** -X (F, Cl, Br, I) e.g., Chloromethane ($CH_3Cl$) - **Alcohols:** -OH (hydroxyl group) e.g., Ethanol ($C_2H_5OH$) - **Aldehydes:** -CHO (aldehyde group) e.g., Ethanal ($CH_3CHO$) - **Ketones:** >C=O (ketone group, within chain) e.g., Propanone ($CH_3COCH_3$) - **Carboxylic Acids:** -COOH (carboxyl group) e.g., Ethanoic Acid ($CH_3COOH$) - **Esters:** -COO- (ester group) e.g., Ethyl ethanoate ($CH_3COOC_2H_5$) ### Isomerism - **Definition:** Compounds having the same molecular formula but different structural formulas. - **Example (Butane and Isobutane):** - $C_4H_{10}$ - n-Butane: $CH_3-CH_2-CH_2-CH_3$ - Isobutane (2-methylpropane): $CH_3-CH(CH_3)-CH_3$ ### Nomenclature (IUPAC) - **Prefix:** Number of carbon atoms (Meth-1, Eth-2, Prop-3, But-4, Pent-5, Hex-6). - **Root word:** Type of carbon chain (alkane, alkene, alkyne). - **Suffix:** Functional group. - **Example:** - $CH_3OH$: Methanol (Meth + an + ol) - $CH_3COOH$: Ethanoic acid (Eth + an + oic acid) ### Chemical Properties of Carbon Compounds - **Combustion:** - Most carbon compounds burn in oxygen to produce $CO_2$, water, heat, and light. - $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + Heat + Light$ - Saturated hydrocarbons burn with a clean flame, unsaturated with a sooty flame. - **Oxidation:** - Alcohols can be oxidised to carboxylic acids by oxidising agents like alkaline $KMnO_4$ or acidified $K_2Cr_2O_7$. - $CH_3CH_2OH \xrightarrow{\text{Alkaline } KMnO_4 \text{ + Heat}} CH_3COOH$ - **Addition Reaction:** - Unsaturated hydrocarbons add hydrogen in the presence of catalysts (Ni, Pd) to form saturated hydrocarbons. (Hydrogenation) - $CH_2=CH_2 + H_2 \xrightarrow{Ni} CH_3-CH_3$ - Used in the hydrogenation of vegetable oils. - **Substitution Reaction:** - Saturated hydrocarbons react with halogens in the presence of sunlight. - $CH_4 + Cl_2 \xrightarrow{\text{Sunlight}} CH_3Cl + HCl$ ### Ethanol and Ethanoic Acid - **Ethanol ($C_2H_5OH$):** - **Properties:** Colourless liquid, pleasant smell, burning taste, miscible with water, good solvent. - **Uses:** Alcoholic beverages, solvent, antiseptic, fuel. - **Reactions:** - **With Sodium:** $2C_2H_5OH + 2Na \rightarrow 2C_2H_5ONa + H_2$ (Sodium ethoxide) - **Dehydration:** $C_2H_5OH \xrightarrow{\text{Hot conc. } H_2SO_4} CH_2=CH_2 + H_2O$ (Elimination reaction) - **Ethanoic Acid ($CH_3COOH$):** - **Properties:** Colourless liquid, sour taste, vinegar-like smell, forms glacial acetic acid below $16.6^\circ C$. - **Uses:** Vinegar (5-8% solution), solvent, in making esters. - **Reactions:** - **Esterification:** Reacts with alcohol in the presence of conc. $H_2SO_4$ to form esters. - $CH_3COOH + C_2H_5OH \xrightarrow{\text{Conc. } H_2SO_4} CH_3COOC_2H_5 + H_2O$ (Ethyl ethanoate) - **With Bases:** $CH_3COOH + NaOH \rightarrow CH_3COONa + H_2O$ - **With Carbonates/Bicarbonates:** $2CH_3COOH + Na_2CO_3 \rightarrow 2CH_3COONa + H_2O + CO_2$ - $CH_3COOH + NaHCO_3 \rightarrow CH_3COONa + H_2O + CO_2$ ### Soaps and Detergents - **Soaps:** - **Definition:** Sodium or potassium salts of long-chain carboxylic acids. - **Structure:** Long hydrocarbon chain (hydrophobic) and ionic end (-COO-Na+) (hydrophilic). - **Cleaning Action:** Forms micelles (cluster of molecules with hydrophobic tails towards oil/grease and hydrophilic heads pointing outwards in water). The micelle traps the dirt and is washed away. - **Limitations:** Do not work well in hard water (forms scum with $Ca^{2+}$ and $Mg^{2+}$ ions). - **Detergents:** - **Definition:** Sodium salts of long-chain benzene sulphonic acids or long-chain alkyl hydrogen sulphates. - **Advantages:** Work well in hard water as they do not form insoluble precipitates with $Ca^{2+}$ and $Mg^{2+}$ ions. - **Types:** Anionic, Cationic, Non-ionic.