中文（繁體）
中文（简体）
English
S6 Chemistry: Organic Reactions and Isomerism (Paper 2: intermediate)
S6 Chemistry: Organic Reactions and Isomerism (Paper 2: intermediate)
Ten intermediate items on isomer counts for pentane and butene, dichloroethane isomers, cis trans isomerism, ester mass, oxidation of a primary alcohol, percentage yield, bromine addition, an alkene formula from its mass, and the limits of the bromine water test.
Direct answers Answers in order: three, three, two, cis and trans, 17.6 g, 74.0, 69.9 percent, 8.0 g, C5H10, and alkynes also decolourise bromine water.
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 pentane C5H12 have?
- FoundationHow many structural isomers does butene C4H8 have, counting chain and position differences?
- FoundationHow many structural isomers does C2H4Cl2 have?
- IntermediateDoes but-2-ene show geometric isomerism, and how many forms are there?
- IntermediateWhat mass of ethyl ethanoate, Mr 88.0, forms from 0.20 mol of ethanol with excess ethanoic acid and concentrated sulphuric acid?
- IntermediatePropan-1-ol is fully oxidised by acidified dichromate. What is the relative molecular mass of the final product?
- ChallengeAn esterification has a theoretical yield of 17.6 g but only 12.3 g is collected. Find the percentage yield.
- ChallengeWhat mass of bromine, Mr 160.0, adds to 0.050 mol of propene?
- ChallengeAn alkene has relative molecular mass 70.0. Find its molecular formula.
- Error redoA student claims that any compound decolourising bromine water must be an alkene. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Three | They are pentane, 2-methylbutane and 2,2-dimethylpropane, one straight chain and two branched. |
| 2 | Three: but-1-ene, but-2-ene and 2-methylpropene | A different double bond position or a branched chain gives a different structure. |
| 3 | Two: 1,1-dichloroethane and 1,2-dichloroethane | Both chlorine atoms on one carbon or one on each carbon gives two different structures. |
| 4 | Yes, cis and trans, that is two forms | The double bond cannot rotate freely, so the two methyl groups on the same side give cis and on opposite sides give trans. |
| 5 | 17.6 g | The mole ratio is one to one, so 0.20 times 88.0 gives 17.6 g. |
| 6 | 74.0, propanoic acid | A primary alcohol becomes an aldehyde and then a carboxylic acid, and propanoic acid C3H6O2 has mass 74.0. |
| 7 | 69.9 percent | 12.3 divided by 17.6 and multiplied by 100 gives 69.9 percent. |
| 8 | 8.0 g | Each double bond takes one bromine molecule, so 0.050 times 160.0 gives 8.0 g. |
| 9 | C5H10 | For an alkene 14.0n equals 70.0, so n is five. |
| 10 | Alkynes and other unsaturated compounds also decolourise bromine water | Fading only shows an unsaturated bond, so the general formula or instrumental analysis is still needed. |
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 →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.