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End of chapter exercises Problem 1: Give one word or phrase for each of the following descriptions: 1. The name of the homologous series to which 2-methylpropene belongs. 2. The name of the functional group that gives alcohols their properties. 3. The group of organic compounds that have acidic properties. 4. The IUPAC name of the organic compound that is found in vinegar. 5. The name of the organic compound that is found in alcoholic beverages. Practise more questions like this Answer 1: 1. Alkenes 2. Hydroxyl group 3. Carboxylic acid 4. Ethanoic acid 5. Ethanol Problem 2: When 1-propanol is oxidised by acidified potassium permanganate, the possible product formed is: propane propanoic acid methyl propanol propyl methanoate (IEB 2004) Practise more questions like this Answer 2: propanoic acid Problem 3: What is the IUPAC name for the compound represented by the following structure? 1,2-dichlorobutane 2,2-dichlorobutane 1,2-dichloro-3-methylpropane 1,1-dichloro-3-methylpropane (IEB 2003) Practise more questions like this Answer 3: 1,2-dichlorobutane Problem 4: Give the structural representation and IUPAC name of all possible isomers for C6H14 (hint: there are 5) Practise more questions like this Answer 4: Problem 5: Write balanced equations for the following reactions: 1. Ethene reacts with bromine (use condensed structural representations) 2. The complete combustion of ethyne gas (used molecular formula) 3. Ethanoic acid ionises in water Practise more questions like this Answer 5: 1. CH2CH2+Br2 → CH2(Br)CH2(Br) ethene + bromine → 1,2-dibromoethane 2. 2C2H2(g)+5O2(g) → 4CO2(g)+2H2O(g) 3. CH3COOH(ℓ)+H2O(ℓ) → CH3COO−(aq)+H3O+(aq) Problem 6: The table below gives the boiling point of ten organic compounds. Compound Molecular formula Boiling Point (°C) CH4 1 −162 methane C2H6 2 −89 ethane C3H8 3 propane 4 butane 5 pentane −42 C4H10 0 C5H12 36 CH4O 6 methanol 64,7 C2H6O 7 ethanol 78,4 C3H8O 8 propan-1-ol 97 C3H8O2 9 propan-1,2-diol 10 propan-1,2,3-triol 188 C3H8O3 290 Table 1 The following questions refer to the compounds shown in the above table. 1. Which of the above compounds are gases at room temperature? 2. What is the reason for the trend of increasing boiling points seen in compounds 1 to 5? 3. Despite the fact that the length of the carbon chain in compounds 8,9 and 10 is the same, the boiling point of propan-1,2,3-triol is much higher than the boiling point of propan-1-ol. What is responsible for this large difference in boiling point? 4. Give the IUPAC name and the structural representation of an isomer of butane. 5. Which one of the compounds is used as a reactant in the preparation of the ester ethyl methanoate? 6. Using structural representation, write an equation for the reaction which produces ethyl methanoate. (IEB 2004) Practise more questions like this Answer 6: 1. Methane, ethane, propane and butane (i.e. compounds 1 - 4) 2. As the alkanes increase in chain length so does their surface area. This leads to stronger intermolecular forces and an increase in boiling point. 3. As each hydroxyl group is added the strength of the intermolecular forces increases. The compound can form more hydrogen bonds. This leads to an increase in the boiling point. 4. 2-methylpropane 5. Ethanol (7) 6. Problem 7: Refer to the numbered diagrams below and then answer the questions that follow. 1. Which one of the above compounds is produced from the fermentation of starches and sugars in plant matter? 2. To which one of the following homologous series does compound 1 belong? 1. esters 2. alcohols 3. aldehydes 4. carboxylic acids 3. The correct IUPAC name for compound 3 is... 1. 1,1-dibromobut-3-yne 2. 4,4-dibromobut-1-yne 3. 2,4-dibromobut-1-yne 4. 4,4-dibromoprop-1-yne 4. What is the correct IUPAC name for compound 4? 1. propanoic acid 2. ethyl methanoate 3. methyl ethanoate 4. methyl propanoate IEB 2005 Practise more questions like this Answer 7: 1. compound 2, ethanol 2. iv) carboxylic acids 3. ii) 4,4-dibromobut-1-yne 4. iii) methyl ethanoate Problem 8: Answer the following questions: 1. Explain the term homologous series. Practise more questions like this Answer 8: 1. A homologous series is a series of compounds with the same general formula. All molecules in this series will contain the same functional groups. For example the alkanes are a homologous series: they have the general formula CnH2n+2; for every extra carbon atom there are two extra hydrogen atoms. Problem 9: Consider the organic compounds labelled A to D. A. CH3CH2CH2CH2CH2CH3 B. C6H6 C. CH3−Cl D. 1. Write a balanced chemical equation for the preparation of compound C using an alkane as one of the reactants. 2. Write down the IUPAC name for compound D. 3. Write down the structural representation of an isomer of compound A that has only FOUR carbon atoms in the longest chain. 4. Write down the structural representation of compound B. Practise more questions like this Answer 9: 1. CH4+Cl2+light → CH3Cl+HCl 2. There are six carbon atoms in the longest chain containing the functional group so the prefix is hex-. The compound is a ketone and the ketone carbon is the second carbon atom, so the suffix is -2-one. There are 2 methyl groups attached to the fourth carbon atom (4,4-dimethyl). The compound is 4,4-dimethylhexan-2-one. 3. The molecular formula of compound A is C6H14. Note that these are the only two possibilities. 4. or or Any one of the above structures is reasonable. Learners can also draw benzene. Problem 10: Chlorine and ethane react to form chloroethane and hydrochloric acid. 1. Write a balanced chemical equation for this reaction, using molecular formulae. 2. Give the structural representation of chloroethane. 3. What type of reaction has taken place in this example? Practise more questions like this Answer 10: 1. Cl2(g)+C2H6(g)+light → C2H5Cl(g)+HCl(ℓ) 2. 3. Substitution Problem 11: Petrol is in fact not pure C8H18 but a mixture of various alkanes. The octane rating of petrol refers to the percentage of the petrol which is C8H18. For example, 93 octane fuel contains 93% C8H18 and 7% other alkanes. The isomer of C8H18 referred to in the octane rating is in fact not octane but 2,2,4-trimethylpentane. 1. Write a balanced equation for the chemical reaction which takes place when C8H18 burns in excess oxygen (complete combustion). 2. Give the general formula of the alkanes. 3. Define the term isomer. 4. Use the information given in this question and your knowledge of naming organic compounds to deduce and draw the full structural formula for 2,2,4trimethylpentane.(I.E.B.) Practise more questions like this Answer 11: 1. 2C8H18(ℓ)+25O2(g) → 16CO2(g)+18H2O(g)+heat 2. CnH2n+2 3. Isomers are two (or more) organic compounds that have the same molecular formula but a different structural formula. 4.