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NAME _____________________________________________________
CLASS ____________________
DUE DATE ____________________
SCHOOL
ASSIGNMENT SUB TOPIC 5.10: TRIGLYCERIDES
The triglycerides are the fats and oils in nature. Generally the solids are saturated fats; the oils the unsaturated fats. We should all cut down on our intake of fats, particularly the saturated ones. Why? They are primarily
responsible for heart disease.
1. (a) What structural feature of a molecule identifies a compound as an ester?
(1)
(b) Write down the full structural formula of the triester made from glycerol and ethanoic acid.
(2)
(c) Give an equation to show what happens when this ester is heated with sodium hydroxide solution.
(2)
2. Below is the structure of a triester present in a naturally occurring substance.
(a) What is the name given to this triester and similar triesters?
_______________________________________________________________________________ (1)
(b) Is this triester likely to be an oil or a fat? Give reasons for your answer.
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(c) The triester was hydrolysed by heating with sodium hydroxide solution, and the resulting solution was neutralised by addition of hydrochloric acid.
(i) Draw structural formulae for the hydrolysis products formed. Use the shortened form for the acid as shown above.
(4)
(ii) Using a text for help, name the acids formed.
____________________________________________________________________________________
____________________________________________________________________________________
___________________________________________________________________________ (3)
(iii) Name the alcohol formed.
___________________________________________________________________________ (1)
(d) How many moles of each product would be obtained from 1 mole of the triester?
_______________________________________________________________________________ (1)
Student note:
Another triester is that formed from glycerol and palmitic acid is:
3. Explain the difference between the following terms, which often appear on food labels.
(a) Saturated fat
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(b) Monounsaturated fat
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_______________________________________________________________________________ (2)
(c) Polyunsaturated fat
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_______________________________________________________________________________ (2)
4. Animal fat is made up almost entirely of saturated fats. One compound present in sheep fat produces only glycerol and stearic acid, CH3(CH2)16COOH, on hydrolysis. Draw out the structural formula of this compound (using the shortened form for the acid chain as in Problem 2).
(3)
5. A food company buys a vegetable oil and converts it to margarine by treatment with hydrogen in the presence of
a metal catalyst. During the process some of the double bonds in the oil are hydrogenated.
(a) Name a suitable catalyst and give conditions under which the hydrogenation could be carried out.
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(b) Assume that the oil contains only the triester shown in problem 2. 1 tonne (1000 kg) of the oil requires 4.90 kg of hydrogen to make margarine. What percentage of the double bonds in the oil have been hydrogenated?
(2)
6. The ester spermaceti is a soft wax that in the past was obtained from the head of the sperm whale. It is used in skin lotions and has the following formula:
O ||
C15H31COC16H33
Write the formula of the carboxylic acid and the alcohol from which spermaceti can be prepared.
Carboxylic acid: _____________________________________________________________________
Alcohol: ___________________________________________________________ (2)
7. Oleic acid is an unsaturated carboxylic acid obtained from the hydrolysis of soya bean oil. The structure of oleic acid is shown below:
CH3(CH2)7CH=CH(CH2)7CO2H
(a) Write the structural formula of a triglyceride that would give oleic acid on hydrolysis.
(2)
(b) When heated, liquid oils may be converted into solid fats, as shown below:
BOIL + A FAT
C
Identify the required reagent A, the substance B, and the condition C necessary for the conversion to occur.
A: ________________________________________________________________________________
B: ________________________________________________________________________________
C: _______________________________________________________________________ (3)
Total /37
ANSWERS SUB TOPIC 5.10: TRIGLYCERIDES
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6.
7.
NAME _____________________________________________________
CLASS ____________________
DUE DATE ____________________
SCHOOL
ASSIGNMENT SUB TOPIC 5.11: CARBOHYDRATES
Carbohydrates are important food stuffs. They are produced by plants through photosynthesis, and are sometimes described as the energy foods. When you eat too much of an energy food the excess is stored in
your body as fat. The more energy rich the food, the more fattening it is. Here is a comparison:
glucose (a carbohydrate), C6H12O6, energy density = 17 kJ g-1
glyceryl trioleate (olive oil), C57H104O6, energy density = 39 kJ g-1
Why the difference? Oils have far less oxygen atoms per carbon atom so are more energy rich. Gram for gram oils and fats are more than twice as fattening as carbohydrates.
Carbohydrates have the general formula, Cx(H2O)y.
1. Trehalose, aspartame, and cyclamate are three substances used as sweeteners.
(a) Which one is the carbohydrate and why?
_______________________________________________________________________________ (1)
(b) Write down the molecular formula for this carbohydrate.
(1)
(c) State the conditions needed to convert the carbohydrate to ethanol.
_______________________________________________________________________________ (2)
(d) Glucose burns in air above 500C. Explain how it is possible for living organisms to carry out this reaction swiftly and efficiently at 37C.
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(e) Write the equation for the conversion of the carbohydrate, glucose, to ethanol.
_______________________________________________________________________________ (1)
2. Sucrose is a natural sweetener derived from sugar cane. The structure of sucrose is shown below:
Sugars may be classified as monosaccharides, disaccharides, or polysaccharides.
(a) State the saccharide classification to which sucrose belongs.
_______________________________________________________________________________ (1)
(b) A crushed sample of sucrose is warmed with ammoniacal silver nitrate solution. State the observation you would expect. Give a reason for your answer.
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(c) Sucrose can be hydrolysed to produce a mixture of fructose (F) and glucose (G). The structures of F and G are shown in open-chain forms below:
(i) State the saccharide classification to which both fructose and glucose belong.
___________________________________________________________________________ (1)
(ii) The mixture of F and G is warmed with ammoniacal silver nitrate solution. State the observation you would expect and name the functional group responsible for it.
____________________________________________________________________________________
___________________________________________________________________________ (2)
STUDENT NOTE:
3. Below are some different structural formulae found in biochemistry text books.
(a) Give the molecular formula of each.
(b) Which are carbohydrates?
(c) Which are the disaccharides?
Write your answers next to the formula.
(24)
4. Consider the structures below:
Using the identifying letters, A, B or C
(a) Which is a monosaccharide? ____________________________ (1)
(b) Which is a polysaccharide? ____________________________ (1)
(c) Which one could be maltose? ____________________________ (1)
(d) Write down the molecular formula of B ____________________________ (1)
(e) Mark in on A its repeating unit (1)
5. Sucrose, C12H22O22, is so soluble in water that a saturated solution at room temperature is only one third solvent by weight. The solubility of sucrose in several solvents at 20C is given.
Solvent Solubility of sucrose
Water
Methanol
Ethanol
Petrol
1 g / 0.5 mL water
1 g / 100 mL methanol
1 g / 170 mL ethanol
insoluble
Can you explain these differences in solubility? Be as specific as possible.
_________________________________________________________________________________________
_________________________________________________________________________________________
_________________________________________________________________________________________
_______________________________________________________________________________ (3)
6. Glucose exists in equilibrium between a cyclic form and an open chain form shown below:
(a) Name the functional groups present in the open form.
_______________________________________________________________________________ (2)
(b) (i) What would you observe if a sample of the above mixture was shaken and warmed with some Tollen’s reagent?
____________________________________________________________________________________
___________________________________________________________________________ (1)
(ii) What type of reaction has the glucose undergone?
___________________________________________________________________________ (1)
(iii) Describe the changes to the above equilibrium resulting from the addition of Tollen’s reagent.
____________________________________________________________________________________
___________________________________________________________________________ (2)
7. The structural formulae of glucose and fructose are shown below:
(a) (i) Circle and name the functional groups present in the two structures above.
___________________________________________________________________________ (1)
(ii) Write down the molecular formulae for both these sugars.
___________________________________________________________________________ (2)
(iii) Explain the high solubility of glucose in water.
____________________________________________________________________________________
___________________________________________________________________________ (2)
(b) Glucose units can chemically bond together to form long chain molecules. Give two examples.
_______________________________________________________________________________ (2)
(c) Glucose, which is found in fruit and honey, is the most abundant sugar found in nature. Why do athletes consume glucose, rather than other sugars, as a source of ‘instant’ energy? Support your answer with a chemical equation.
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(d) What would you observe if glucose was treated with:
(i) acidified dichromate ions
___________________________________________________________________________ (1)
(ii) ammoniacal silver nitrate solution?
___________________________________________________________________________ (1)
(e) Can fructose undergo the two reactions in (d) above? Explain.
_________________________________________________________________________________________
_________________________________________________________________________________________
_______________________________________________________________________________ (2)
(f) (i) Draw the structure of the compound formed when fructose is treated with some acetic acid, in the presence of a few drops of concentrated sulfuric acid.
(2)
(ii) Name the new functional group produced. _______________________________ (1)
(iii) What name is given to the reaction? _______________________________ (1)
(iv) What is the function of the concentrated sulfuric acid?
___________________________________________________________________________ (1)
Total /69
ANSWERS SUB TOPIC 5.11: CARBOHYDRATES
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