These eight questions use original compounds and equations. Draw and write your own answer before you open the explanation.
The set belongs to carbon compounds. The timed version is in the timed original practice session builder.
Questions
Q1. State the homologous series of (a) C₇H₁₆ and (b) C₃H₇COOH.
Answer
(a) Alkane, because C₇H₁₆ fits CₙH₂ₙ₊₂ with n = 7 (2 × 7 + 2 = 16).
(b) Carboxylic acid, because it contains –COOH. It has four carbons in total, so it is butanoic acid.
Q2. Name CH₃CH(CH₃)CH₂CH₃, and draw its full structural formula.
Answer
The longest chain has four carbons. A methyl group is on carbon 2, which is the lowest number from either end. The name is 2-methylbutane.
Draw carbons 1 to 4 in a line, add a CH₃ to carbon 2, and fill with hydrogens so that every carbon has four bonds.
Q3. Draw and name the isomers of C₄H₈ that are alkenes.
Answer
There are three: but-1-ene, CH₂=CHCH₂CH₃, but-2-ene, CH₃CH=CHCH₃, and 2-methylpropene, CH₂=C(CH₃)CH₃.
The first two differ in the position of the double bond. The third has a branched chain.
Q4. Write the equation for the complete combustion of butane, C₄H₁₀.
Answer
Carbon gives 4 CO₂ and hydrogen gives 5 H₂O. Oxygen on the right is 8 + 5 = 13, so the equation needs 6.5 O₂. Double everything to avoid a fraction.
2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O
Q5. Propene is shaken with bromine water. State the observation and write the equation.
Answer
The brown colour disappears, because bromine adds across the C=C bond.
CH₃CH=CH₂ + Br₂ → CH₃CHBr–CH₂Br. One product forms, which shows addition.
Q6. Propanoic acid reacts with methanol in the presence of concentrated sulfuric acid. Name the ester and state one observation.
Answer
The ester is methyl propanoate. The alkyl part comes from the alcohol (methyl) and the stem from the acid (propanoate). The mixture gives a sweet, fruity smell.
Q7. Plan a route from ethene to ethanoic acid. Name the intermediate and the reagent for each step.
Answer
Step 1: hydrate ethene with steam, using a phosphoric acid catalyst, high temperature and pressure, to give ethanol.
Step 2: oxidise ethanol with acidified potassium manganate(VII) and heat to give ethanoic acid. The intermediate is ethanol.
Q8. Draw the repeating unit of poly(propene), and give the monomer’s name.
Answer
The monomer is propene, CH₂=CH–CH₃. Open the double bond: –[CH₂–CH(CH₃)]ₙ–.
There is no C=C left in the chain, so poly(propene) does not decolourise bromine water.
If you got these wrong
Go back to the lesson for the skill you missed.
- Q1: identifying homologous series and functional groups.
- Q2: naming and drawing organic structures.
- Q3: distinguishing isomers.
- Q4, Q5 and Q6: writing characteristic organic reactions.
- Q7: planning a reaction pathway.
- Q8: comparing polymers and monomers.
Log each slip in the mistake log and paper-error review. For a teacher to work through new questions with you, see online one-to-one Chemistry tuition.