11.6. Alcohols
A subsection of Chemistry, 0620, through 11. Organic chemistry
Listing 10 of 234 questions
Biogas is made by fermenting animal and vegetable waste. The table shows the percentage composition of the gases present in a sample of biogas. substance present percentage present in biogas carbon dioxide hydrogen 1.0 methane 61.5 nitrogen 8.5 water vapour 2.2 other substances 0.1 total 100.0 Deduce the percentage of carbondioxide present in this sample of biogas. During the fermentation, carbon dioxide reacts with hydrogen to produce methane and water. Complete the chemical equation for this reaction. CO2 + H2 CH4 + H2O Methane and ethane are in the same homologous series. What is meant by the term homologous series? Draw a dot-and-cross diagram to show the electron arrangement in a molecule of methane, CH4. Show outer shell electrons only.  Helium and hydrogen can both be used to fill balloons. Suggest one advantage of using helium rather than hydrogen to fill balloons. The biogas fermentation mixture contains a small amount of compoundC. The structure of compoundC is shown. C H C H H H H H H H H O H C C C S S C On the structure shown, draw a circle around a functional group which reacts with aqueousbromine. How many different types of atoms are present in compoundC? Ethanol is produced by fermentation of a mixture of plant sugars. Describe how ethanol can be separated from the rest of the fermentation mixture by fractional distillation. In your answer: ● ● describe how to do the fractional distillation ● ● explain how ethanol is separated from the rest of the fermentation mixture using fractional distillation. 
0620_w19_qp_32
THEORY
2019
Paper 3, Variant 2
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This question is about ethanol. Ethanol that is suitable for use as a fuel can be manufactured from sugars such as glucose, C6H12O6, by a two-step process. Describe how this can be done. In your answer, include: ● ● an equation for the reaction in which ethanol is formed ● ● the essential conditions for the reaction in which ethanol is formed ● ● the name of the process used to obtain ethanol that is pure enough to use as a fuel from the reaction mixture. The equation for the complete combustion of ethanol is shown. H C H H C H H O H O O + H O H + O C O Use the bond energies in the table to calculate the energy change, in kJ / mol, for the complete combustion of ethanol. bond bond energy in kJ / mol C–C C–H C–O C=O O–H O=O ● ● Energy needed to break bonds.  kJ ● ● Energy released when bonds are formed.  kJ ● ● Energy change for the complete combustion of ethanol.  energy change = kJ / mol  Ethanol can be oxidised by hydrogenperoxide to form ethanal, CH3CHO. A catalyst for this reaction is Fe3+. What is meant by the term catalyst ? The structure of ethanal is shown. H C H H C H O Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ethanal. Show outer shell electrons only. H H H H C C O  The table gives the boiling points of ethanal and ethanol. substance boiling point / °C ethanal ethanol In terms of attractive forces between particles, suggest why ethanal has a lower boiling point than ethanol. Ethene gas reacts with steam to form gaseous ethanol. C2H4+ H2OCH3CH2OHThe reaction can reach a position of equilibrium. The forward reaction is exothermic. State and explain the effect of increasing the pressure on the position of equilibrium. All other conditions are unchanged. Increasing the pressure of a gas increases its concentration. State and explain the effect of increasing the pressure on the rate of the reaction. All other conditions are unchanged. State and explain the effect of increasing the temperature on the position of equilibrium. All other conditions are unchanged. 
0620_w19_qp_41
THEORY
2019
Paper 4, Variant 1
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