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Organic Chemistry Questions and Answers (O level Chemistry)

Organic Chemistry Questions and Answers (O level Chemistry)

Organic chemistry deals with the compounds of carbon, except for carbonates and carbon dioxide. The following is a list of organic chemistry questions and expected answers for O level chemistry students. The first question is about ethanol (from the alcohols functional group) and ethene (from the alkenes functional group). The second question is about polymers.



Question 1

Ethanol, CH3CH2OH, is a liquid fuel which can be manufactured either from glucose,
C6H12O6, or from ethene.

  1. Briefly describe the manufacture of ethanol from glucose.
    Include the balanced equation in your answer.
    1. Draw the displayed formula for ethene.
    2. Name the substance that reacts with ethene to make ethanol.
    3. Give the conditions needed for this reaction.

Solution 1

  1. Ethanol is manufactured by the fermentation of sugar solution using an enzyme zymase in yeast. The yeast breaks down the sugar by anaerobic respiration to produce carbon dioxide and ethanol.

    glucose → ethanol + carbon dioxide

    C6H12O6
    (aq) → 2C2H5OH(l) + 2CO2(g)

    The ethanol produced is then purified by fractional distillation.

    1. Organic Chemistry Questions and Answers (O level Chemistry)

    2. Water
    3. 300° C temperature , 70 atm pressure and phosphoric acid catalyst.


Question 2

More than 60 000 plastic materials, or polymers, are in use. The table gives some information about five important polymers.

PolymerDensity in kg/m3maximum usable temperature °Csolubility in organic solvents
low density poly(ethene)92085soluble above 80 °C
high density poly(ethene)960120soluble above 80 °C
poly(phenylethene)105065soluble
poly(chloroethene)139060soluble
poly(propene)900150insoluble
  1. Which polymer would be most suited for making a pipe to carry lubricating oil at 100 °C? Give two reasons for your answer.
  2. State one use for poly(ethene).
  3. Describe some of the problems of the disposal of waste polymers (plastics).
  4. Terylene is a condensation polymer. The structure of Terylene is shown below.
  5. Terylene

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    1. What is the name of the linkage shown in the structure of Terylene?
    2. Name a natural macromolecule that contains the same linkage as Terylene.
  6. Draw the structure of a polyamide such as nylon.

Solution 2

  1. poly(propene). Because it is insoluble in organic solvents such as oil and its maximum usable temperature is greater than 100° C
  2. Making food packaging material
  3. Plastics are non biodegradable so when they are disposed they lie around forever and cause problems such as:
    • choking birds, fish and other animals that try to eat them.
    • filling up the animals stomachs so that the animals cannot eat proper food, and starve to death.
    • they clog up drains, and sewers, and cause flooding.
    • they blow into trees and onto beaches and make the place looks a mess.
    1. Ester linkage
    2. Rubber
  4. Nylon

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