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Chemistry 30

Chemistry 30 · Worksheets

Organic chemistry

Ten questions of mixed difficulty, covering Organic chemistry. Print it, or work through it on screen — the answer key starts on its own page.

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Organic chemistry

Chemistry 30 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. A carboxylic acid reacts with an alcohol to produce

    1. a) a ketone and water
    2. b) an ester and water
    3. c) an aldehyde and hydrogen
    4. d) an ether and oxygen

  2. Two compounds with the same molecular formula but different structures are

    1. a) polymers
    2. b) isotopes
    3. c) isomers
    4. d) allotropes

  3. When bromine reacts with ethene, C₂H₄, the reaction is

    1. a) an addition reaction, because the double bond opens up
    2. b) an elimination reaction
    3. c) a combustion reaction
    4. d) a substitution reaction, because bromine replaces hydrogen

  4. Polyethene is formed from ethene by

    1. a) combustion
    2. b) addition polymerization, with no other product
    3. c) condensation polymerization, releasing water
    4. d) substitution, releasing hydrogen

  5. The IUPAC name for CH₃CH(CH₃)CH₂CH₃ is

    1. a) 3-methylbutane
    2. b) 2-methylpropane
    3. c) pentane
    4. d) 2-methylbutane

  6. The IUPAC name for CH₃CH₂CH₃ is

    1. a) butane
    2. b) propyne
    3. c) propene
    4. d) propane

  7. A ketone differs from an aldehyde because its carbonyl group is

    1. a) bonded to carbons on both sides, rather than at the end of the chain
    2. b) always attached to a benzene ring
    3. c) bonded to a hydroxyl group
    4. d) a double bond between two carbons

  8. A hydrocarbon is described as unsaturated when it

    1. a) dissolves readily in water
    2. b) contains only single bonds
    3. c) contains at least one double or triple bond between carbons
    4. d) contains an oxygen atom

  9. A compound containing an −OH functional group attached to a carbon chain is

    1. a) an ether
    2. b) a carboxylic acid
    3. c) an aldehyde
    4. d) an alcohol

  10. In the complete combustion of propane, C₃H₈ + __O₂ → 3CO₂ + 4H₂O, the coefficient of O₂ is

    1. a) 4
    2. b) 5
    3. c) 7
    4. d) 3

Answer key · Organic chemistry

Chemistry 30 · maddyhelps.com

  1. b) an ester and water — This is esterification, a condensation reaction: the two molecules join and a water molecule is released. Esters are responsible for many fruit smells and flavours.
  2. c) isomers — Isomers share a formula but arrange the atoms differently, which is why C₄H₁₀ can be butane or methylpropane, with different properties. Isotopes are atoms of one element differing in neutrons.
  3. a) an addition reaction, because the double bond opens up — The double bond breaks open and a bromine atom adds to each carbon, giving 1,2-dibromoethane. Alkanes, with no double bond available, undergo substitution instead.
  4. b) addition polymerization, with no other product — The double bonds in many ethene molecules open and link together into one long chain, with nothing left over. Condensation polymerization, which makes nylon and polyesters, releases a small molecule such as water at each link.
  5. d) 2-methylbutane — The longest chain is four carbons (butane) with a methyl branch. Numbering from the end that reaches the branch first puts it on carbon 2, so 2-methylbutane. Numbering the other way gives 3-methylbutane, which breaks the lowest-locant rule.
  6. d) propane — Three carbons gives the stem prop-, and all single bonds gives the ending -ane. The -ene and -yne endings mean a double and a triple bond.
  7. a) bonded to carbons on both sides, rather than at the end of the chain — Both families contain C=O. In an aldehyde it sits at the end of the chain with a hydrogen attached; in a ketone it is between two carbon atoms.
  8. c) contains at least one double or triple bond between carbons — Unsaturated means the carbons are not holding their maximum number of hydrogens, because some bonding is used up in a double or triple bond. Those bonds are also what make addition reactions possible.
  9. d) an alcohol — The hydroxyl group defines the alcohol family, and its name ends in -ol. A carboxylic acid is −COOH, which is a carbonyl and a hydroxyl on the same carbon.
  10. b) 5 — The products hold 3×2 = 6 oxygen atoms in CO₂ and 4 in H₂O, so 10 oxygen atoms are needed — that is 5 O₂ molecules. Complete combustion of a hydrocarbon always gives carbon dioxide and water.