WASSCE Chemistry · Paper 1 style

Hydrocarbons

One sample question with the full working. 1 more in the app, with instant feedback and repair sessions for the traps below.

The first member of the alkane series is

Aethene
Bethane
Cmethane
Dpropane

Show the answer and working

Answer: C

Alkanes: methane, ethane, propane…

Trap A Confuses homologous series and functional groups: Alkanes CₙH₂ₙ₊₂ (C–C only); alkenes CₙH₂ₙ (C=C); alkynes CₙH₂ₙ₋₂ (C≡C); alkanols R–OH; alkanoic acids R–COOH; esters R–COO–R'. Identify the functional group first.

Trap B Miscounts atoms, electrons or steps: After working, check by counting back: total electrons = atomic number; atoms in the formula match the subscripts; number of half-lives = time ÷ half-life.

Trap D Mixes up a pair of similar chemical terms: Keep a list of confusable pairs with one defining feature each and a hook. Underline the key word in the stem and check it against the definition, not the sound of the name.

Traps in Hydrocarbons

Confuses homologous series and functional groups
Alkanes CₙH₂ₙ₊₂ (C–C only); alkenes CₙH₂ₙ (C=C); alkynes CₙH₂ₙ₋₂ (C≡C); alkanols R–OH; alkanoic acids R–COOH; esters R–COO–R'. Identify the functional group first.
Miscounts atoms, electrons or steps
After working, check by counting back: total electrons = atomic number; atoms in the formula match the subscripts; number of half-lives = time ÷ half-life.
Mixes up a pair of similar chemical terms
Keep a list of confusable pairs with one defining feature each and a hook. Underline the key word in the stem and check it against the definition, not the sound of the name.

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