O-LevelChemistryOrganic Chemistry5070/22 · May/June 2017 · Q1010 Marks
The table shows some information about the homologous series of unbranched alcohols. name | structure | boiling point / °C ---|---|--- methanol | CH₃OH | 65 ethanol | CH₃CH₂OH | 79 propanol | CH₃CH₂CH₂OH | 97 butanol | CH₃CH₂CH₂CH₂OH | 117 pentanol | CH₃CH₂CH₂CH₂CH₂OH | 138
- (a)(i)One of the characteristics of a homologous series is that it has a general formula. What is the general formula for the homologous series of unbranched alcohols?[1]
- (a)(ii)Predict the boiling point of hexanol, an alcohol with six carbon atoms per molecule.[1]
- (b)Describe the manufacture of ethanol by the fermentation of aqueous glucose.[3]
- (c)Butanol reacts with ethanoic acid to make an ester. Name and draw the structure of this ester. Show all of the atoms and all of the bonds within the ester linkage. name structure[2]
- (d)Ethanol is a gas at 100 °C. Describe the changes in the arrangement and movement of the molecules when ethanol is cooled from 100°C to 25 °C.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- B10(a)(i) CnH2n+1OH / CnH2n+2O
- B10(a)(ii) Any value between 154 – 164 (°C) (inclusive of these values)
- B10(b) (Add) yeast (1) Temperature between 5 and 40 °C / no oxygen present / anaerobic (1) (Fractionally) distil (to get ethanol) (1)
- B10(c) Butyl ethanoate (1) HO ΗΗΗΗ H-C-C-O-C-C-C-C-H (1) H ΗΗΗΗ
- B10(d) They get slower / they move less rapidly (when temperature decreases) / molecules slow down (when temperature decreases) / molecules have less kinetic energy (when temperature decreases) (1) They / molecules get closer together (when temperature decreases) (1) They / molecules arranged less randomly / less irregularly (when temperature decreases) (1)
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