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S6 Chemistry: Organic Reactions and Isomerism (Paper 3: challenge)
S6 Chemistry: Organic Reactions and Isomerism (Paper 3: challenge)
Ten challenge items on hexane isomers, degree of unsaturation, percentage carbon by mass, carbon dioxide volume from combustion, ester mass, bromine addition, fermentation yield, a formula from combustion data, homologous series, and branching against boiling point.
Direct answers Answers in order: five, three, 82.8 percent, 6.00 dm3, 130.0, 1.12 g, 82.8 g, C4H10, a homologous series, and branching reduces contact area and weakens the forces.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S6 Chemistry: Organic Reactions and Isomerism |
| Level | S6 |
02 Questions (10 items)
- FoundationHow many structural isomers does hexane C6H14 have?
- FoundationWhat is the degree of unsaturation of the hydrocarbon C8H12?
- FoundationWhat percentage by mass of butane is carbon?
- IntermediateWhat volume of carbon dioxide at 24.0 dm3 per mol comes from burning 0.050 mol of pentane completely?
- IntermediateWhat is the relative molecular mass of the ester formed from butan-1-ol and propanoic acid?
- ChallengeWhat mass of an alkene of Mr 56.0 reacts fully with 3.2 g of bromine, Mr 160.0?
- ChallengeFermentation of 1.00 mol of glucose at 90.0 percent yield gives what mass of ethanol?
- ChallengeBurning 0.10 mol of a hydrocarbon gives 0.40 mol of carbon dioxide and 0.50 mol of water. Find its formula.
- IntermediatePropane and butane differ by one CH2 unit. What is their relationship?
- Error redoWhy does 2-methylpropane boil lower than butane although both are C4H10?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Five | There are one straight chain, two singly branched and two doubly branched structures. |
| 2 | Three | Two times eight plus two minus twelve, all divided by two, gives three. |
| 3 | 82.8 percent | 48.0 divided by 58.0 and multiplied by 100 gives 82.8 percent. |
| 4 | 6.00 dm3 | Each mole of pentane gives five moles of carbon dioxide, so 0.050 times five times 24.0 gives 6.00 dm3. |
| 5 | 130.0, butyl propanoate | For C7H14O2 the parts are 84.0, 14.0 and 32.0, giving 130.0. |
| 6 | 1.12 g | The bromine is 0.020 mol and so is the alkene, giving 0.020 times 56.0, that is 1.12 g. |
| 7 | 82.8 g | Two moles of ethanol are expected, and at 90.0 percent that is 1.80 mol, so 1.80 times 46.0 gives 82.8 g. |
| 8 | C4H10 | Each mole of the hydrocarbon holds four moles of carbon and ten of hydrogen, so the formula is C4H10. |
| 9 | They are members of the same homologous series | Members of a homologous series share a general formula and similar chemistry, with physical properties changing steadily along the chain. |
| 10 | The branched molecule is more compact, so there is less contact area and weaker forces between molecules | Van der Waals forces grow with contact area, so a branched isomer with less contact area boils lower. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Write the molecular formula and functional group first, decide the reaction type, then do the mole calculation.Tutor Registration →
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