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Quiz Organic Chemistry: carbon, alkanes and functional groups

Test your basics in organic chemistry: carbon bonds, alkanes, functional groups, isomers and IUPAC names. Eleven verified questions with explainers.

12 questions~6 minen
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How many covalent bonds does a carbon atom typically form?

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  1. Q1. How many covalent bonds does a carbon atom typically form?

    • 2
    • 3
    • 4
    • 6
    Carbon has 4 valence electrons and almost always forms 4 covalent bonds. This tetravalence is what allows the immense diversity of organic molecules and life chemistry.

  2. Q2. What is the general formula for an alkane?

    • CₙH₂ₙ
    • CₙH₂ₙ₊₂
    • CₙH₂ₙ₋₂
    • CₙHₙ
    Saturated alkanes follow CₙH₂ₙ₊₂. Methane is CH₄ (n=1), ethane C₂H₆, propane C₃H₈, butane C₄H₁₀. Only single C-C bonds, no rings.

  3. Q3. Which functional group defines an alcohol?

    • −COOH
    • −OH
    • −NH₂
    • −CHO
    Alcohols carry a hydroxyl group −OH bonded to a saturated carbon. Ethanol (CH₃CH₂OH) is the alcohol in beverages; methanol (CH₃OH) is toxic and used as solvent or fuel.

  4. Q4. What is the simplest alkene?

    • Methane
    • Ethylene (ethene)
    • Acetylene
    • Propane
    Ethylene C₂H₄ is the simplest alkene, with one C=C double bond. It is the most produced organic compound in industry (~200 million tons/year) and a plant ripening hormone.

  5. Q5. Which group is characteristic of carboxylic acids?

    • −OH
    • −COOH
    • −CO−
    • −NO₂
    The carboxyl group −COOH defines carboxylic acids. Acetic acid CH₃COOH gives vinegar its sour taste (pKa ≈ 4.76) and is produced by acetic-acid bacteria.

  6. Q6. What kind of isomers share the same molecular formula but different connectivity?

    • Stereoisomers
    • Structural isomers
    • Enantiomers
    • Conformers
    Structural (constitutional) isomers have the same formula but a different atom connectivity. C₄H₁₀ has two: n-butane (linear) and isobutane (branched), with different boiling points.

  7. Q7. Which element is always present in organic compounds?

    • Nitrogen
    • Carbon
    • Oxygen
    • Sulfur
    Carbon is the defining element of organic chemistry, almost always paired with hydrogen. Exceptions like CO₂ or carbonates are usually classified as inorganic by convention.

  8. Q8. What is the hybridization of carbon in methane (CH₄)?

    • sp
    • sp²
    • sp³
    • sp³d
    In CH₄, carbon is sp³ hybridized with four equivalent orbitals pointing to the corners of a tetrahedron. The H-C-H angle is 109.5°, predicted by VSEPR theory.

  9. Q9. Which compound is an aldehyde?

    • CH₃COOH
    • CH₃CHO
    • CH₃OCH₃
    • CH₃NH₂
    CH₃CHO is acetaldehyde, containing the −CHO group at a terminal carbon. It is a metabolite of ethanol oxidation in the liver and largely responsible for hangovers.

  10. Q10. What does the IUPAC suffix '-ene' indicate?

    • A triple bond
    • A double bond
    • An alcohol
    • A ring
    The '-ene' suffix marks a C=C double bond (alkene), as in propene CH₂=CH−CH₃. '-yne' indicates a triple bond, '-ane' a saturated chain.

  11. Q11. How many carbon atoms are in benzene?

    • 4
    • 5
    • 6
    • 8
    Benzene C₆H₆ is a planar ring of 6 carbons with delocalized π electrons. Friedrich August Kekulé proposed its cyclic structure in 1865 after dreaming of a snake biting its tail.

  12. Q12. Which pair are enantiomers?

    • cis/trans 2-butene
    • n-butane / isobutane
    • D-glucose / L-glucose
    • Ethanol / dimethyl ether
    D-glucose and L-glucose are non-superimposable mirror images — enantiomers. Living organisms almost exclusively use D-glucose for metabolism (~16 kJ/g energy yield).

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