11.6. Alcohols
A subsection of Chemistry, 0620, through 11. Organic chemistry
Listing 10 of 234 questions
For Examiner's Use The alcohols form a homologous series. The first four members are methanol, ethanol, propan-1-ol and butan-1-ol. One characteristic of a homologous series is that the physical properties vary in a predictable way. The table below gives the heats of combustion of the first three alcohols. alcohol formula heat of combustion in kJ / mol methanol CH3OH -730 ethanol CH3-CH2-OH -1370 propan-1-ol CH3-CH2-CH2-OH -2020 butan-1-ol CH3-CH2-CH2-CH2-OH The minus sign indicates that there is less chemical energy in the products than in the reactants. What form of energy is given out by the reaction? Is the reaction exothermic or endothermic? Complete the equation for the complete combustion of ethanol. C2H5OH + O2 → + For Examiner's Use Determine the heat of combustion of butan-1-ol by plotting the heats of combustion of the first three alcohols against the number of carbon atoms per molecule. –700 –800 –900 –1000 –1100 –1200 –1300 –1400 –1500 –1600 –1700 –1800 –1900 –2000 –2100 –2200 –2300 –2400 –2500 –2600 –2700 –2800 number of carbon atoms per molecule heat of combustion / kJ / mol The heat of combustion of butan-1-ol = kJ / mol For Examiner's Use Describe two other characteristics of homologous series. Give the name and structural formula of an isomer of propan-1-ol. structural formula name Methanol is made from carbon monoxide. CO+ 2H2CH3OHthe forward reaction is exothermic Describe how hydrogen is obtained from alkanes. Suggest a method of making carbon monoxide from methane. Which condition, high or low pressure, would give the maximum yield of methanol? Give a reason for your choice. pressure reason For each of the following predict the name of the organic product. reaction between methanol and ethanoic acid oxidation of propan-1-ol by potassium dichromate( removal of H2O from ethanol
0620_w07_qp_3
THEORY
2007
Paper 3, Variant 0
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Ethene, C2H4, is manufactured by cracking petroleum fractions. What do you understand by the term petroleum fraction ? Complete the equation for the manufacture of ethene from dodecane, C12H26. C12H26 → C2H4 + Two fractions obtained from the distillation of petroleum are refi nery gas and gasoline. State one use of each of these fractions. refi nery gas gasoline Ethene is an unsaturated hydrocarbon. What do you understand by the following terms? unsaturated hydrocarbon Ethene is used to make ethanol. Which of these reactions is used to make ethanol from ethene? Tick one box. catalytic addition of steam fermentation oxidation using oxygen reduction using hydrogen Draw the structure of ethanol showing all atoms and bonds. Ethene is used to make poly. Complete the following sentences about this reaction. Use words from the list below. additions carbohydrates catalysts monomers polymers The ethene molecules which join to form polyare the . The polymolecules formed are .
0620_w10_qp_21
THEORY
2010
Paper 2, Variant 1
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The alcohols form an homologous series. Give three characteristics of an homologous series. The following two alcohols are members of the series and they are isomers. CH3 — CH2 — CH2 — CH2 — OH and (CH3)2CH — CH2OH Explain why they are isomers. Give the structural formula of another alcohol which is also an isomer of these alcohols. Copper(oxide can oxidise butan-1-ol to liquid X whose pH is 4. liquid X formed by oxidation of butan-1-ol. heat mineral wool soaked in butan-1-ol copper(oxide Name another reagent which can oxidise butan-1-ol. What type of compound is liquid X and what is its formula? type of compound formula of liquid X The alcohol ethanol can be made by fermentation. Yeast is added to aqueous glucose. C6H12O6→ 2C2H5OH+ 2CO2Carbon dioxide is given off and the mixture becomes warm as the reaction is exothermic. The graph shows how the rate of reaction varies over several days. rate of reaction time Suggest a method of measuring the rate of this reaction. Why does the rate increase initially? Suggest two reasons why the rate eventually decreases. Why is fermentation carried out in the absence of air?
0620_w10_qp_32
THEORY
2010
Paper 3, Variant 2
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Questions Discovered
234