HSC Chemistry — Module 7
Hydrocarbons — Flashcards & Quiz
Hydrocarbons are the simplest organic molecules — compounds of carbon and hydrogen only — and they form the basis of the HSC Chemistry Module 7 organic pathway. You need to distinguish alkanes (saturated, substitution), alkenes (C=C, addition), alkynes (C≡C) and cyclic forms, predict combustion products, balance combustion equations, and explain structural and geometric isomerism. The trend in boiling point and solubility with chain length is exam-standard.
Sample Flashcards
Q1: What are alkanes, alkenes and alkynes?
Alkanes: saturated hydrocarbons with only single C-C bonds. General formula CₙH₂ₙ₊₂. Alkenes: unsaturated with at least one C=C double bond. General formula CₙH₂ₙ. Alkynes: unsaturated with at least one C≡C triple bond. General formula CₙH₂ₙ₋₂.
Q2: How do boiling points change in a homologous series?
Within a homologous series, boiling point INCREASES as chain length increases. Longer chains = more electrons = stronger dispersion forces = more energy needed to separate molecules. Branching DECREASES boiling point because the molecule is more compact with less surface area.
Q3: Why is carbon able to form such a large variety of compounds?
Carbon has 4 valence electrons and can form 4 stable covalent bonds. It can bond to other carbon atoms to form chains, branches and rings of virtually unlimited length. It bonds to many other elements (H, O, N, S, halogens). This versatility enables millions of organic compounds.
Sample Quiz Questions
Q1: Alkanes are unsaturated hydrocarbons.
Answer: FALSE
Alkanes are SATURATED — they contain only single C-C bonds. Alkenes and alkynes are unsaturated (contain double or triple bonds).
Q2: The general formula for alkenes is CₙH₂ₙ.
Answer: TRUE
Alkenes follow the general formula CₙH₂ₙ (e.g. ethene C₂H₄, propene C₃H₆). This is due to the one C=C double bond.
Q3: Boiling point decreases as carbon chain length increases in a homologous series.
Answer: FALSE
Boiling point INCREASES with chain length because longer chains have more electrons and stronger dispersion forces.
Related Concepts
Last updated: March 2026 · 3 flashcards · 5 quiz questions