Carbon and its Compounds

Alkene

Step 1: Ethene has the formula C₂H₄ with 2 carbon atoms and 4 hydrogen atoms. Step 2: The general formula for alkenes is CₙH₂ₙ, and C₂H₄ fits this pattern (n=2). Step 3: Ethene contains a double bond between the two carbon atoms (C=C). Step 4: Hydrocarbons with double bonds are called alkenes and are unsaturated. Wrong options: Alkanes have single bonds only, alkynes have triple bonds, aromatic compounds have ring structure with delocalized electrons.

-OH

Step 1: Alcohols are organic compounds containing the hydroxyl functional group. Step 2: The hydroxyl group consists of one oxygen atom bonded to one hydrogen atom (-OH). Step 3: This group is attached to a carbon atom in the hydrocarbon chain. Step 4: Examples include methanol (CH₃OH) and ethanol (C₂H₅OH). Wrong options: -CHO is aldehyde group, -COOH is carboxylic acid group, -CO- is ketone group.

Acetic acid

Step 1: Ethanoic acid has the formula CH₃COOH and contains 2 carbon atoms. Step 2: The common name 'acetic acid' comes from the Latin word 'acetum' meaning vinegar. Step 3: Vinegar contains 5-8% acetic acid in water solution. Step 4: Pure ethanoic acid is called glacial acetic acid because it freezes in cold weather. Wrong options: Formic acid is methanoic acid (HCOOH), citric acid is found in citrus fruits, lactic acid is found in sour milk.

Carbon dioxide

Step 1: Ethanoic acid is a weak acid that reacts with carbonates. Step 2: The reaction is: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂. Step 3: Carbon dioxide gas is evolved, which turns lime water milky. Step 4: This is a characteristic test for acids - they produce CO₂ with carbonates. Wrong options: Hydrogen is produced with metals, oxygen is not produced in this reaction, carbon monoxide is toxic and not formed here.