CHEMISTRY TASK


GRADE 12 

QUESTIONS

Alcohols are used in a variety of chemical reactions and as preservatives in certain medicines. All alcohols are toxic. Although ethanol is the least toxic of all alcohols, it is still poisonous substance. It is rapidly absorbed into the blood. High blood alcohol levels can cause brain poisoning. The body can reduce high blood alcohols levels by oxidising the alcohol. Contrary to what people believe, alcohol is a depressant and not a stimulant.

The following table indicates the effects of various blood alcohol levels:

% per volume Effect
0.005-0.15 Loss of coordination 
0.15-0.20 Severe intoxication
0.20-.40 Loss of consciousness
0.50 Death

The liver enzyme, ADH, catalyses the oxidation of ethanol to ethanal and then to non-toxic ethanoic acid. The liver is able to remove only 28 grams of pure alcohol per hour.

7.1. Write down the names of the homologous series to which the compounds ethanal  and

ethanoic acid respectively belong.                                                                                   (2)

7.2. Write down the structural formula of ethanal.                                                              (2)

7.3. Alcohols are prepared by the hydration of alkanes. Use structural formulae to write

down the equation which represents the formation of ethanol.                                       (3)

7.4. The warning on the labels of certain medicines reads as follows:

       The effect of this medicine is aggravated by the simultaneous intake of alcohol.

Use the information in the passage above to justify this warning.                                   (4)

[11]

QUESTIONS

Five alcohols represented by letters A-E are listed in the table below.

A Methanol B Ethanol
C Propan-1-ol D Butan-2-ol
E 2-methlypropan-2-ol

8.1. Which one of the above alcohols is a secondary alcohol?                                              (1)

Write down only the letter that represents the alcohol

8.2. The letter E represents 2-methlpropan-2-ol. For this alcohol write down the following:

8.2.1. Its structural formula                                                                                  (2)

8.2.2. The letter in the table that represents one of its structural isomers.       (1)

8.3. Viscosity is a measure of a fluid resistance to flow. Learners conduct investigation to

compare the viscosities of the first three alcohols (A-C) in the table below.

Alcohol Flow time(s)
A Methanol 4,0
B Ethanol 7,9
C Propan-1-ol 14,3

8.3.1. Formulate an investigative question.                                                                             (2)

8.3.2. Which one of the alcohols (A, B or C) has the highest viscosity? Use the data in the

table to give a reason for the answer.                                                                           (2)

8.3.3. Refer to the intermolecular forces of the three alcohols (A, B and C) to explain the

trend in viscosities as shown in the table.                                                                      (2)

8.3.4. Lubricants reduce friction. Which one of alcohols (A, B or C) will be the best lubricant?                                                                                                                                            (1)

8.4. Which one of 2-methylpropan-2-ol and butan-2-ol has the higher viscosity                    (1)

8.5. Refer to intermolecular forces to explain the answer to 8.4.                                           (2)

[14]

Comments
  1. bonolo says:

    That’s great…

    Like

  2. Joyce Masilela says:

    Thanks

    Like

  3. Zpozethu says:

    Physical sciences 2016 task 2

    Like

  4. Molefi Mofokeng says:

    So where do we get the correct answers

    Like

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