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MECH U3/4 > Fats > Flashcards

Fats Flashcards

1
Q

Explain why soaps do not function very effectively in hard water.

A

The surfactant ions precipitate with calcium or magnesium ions. Prevents soap from interacting with water/removes the surfactant ion from the system or similar

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2
Q

Name and explain the origin of the predominant attractive force exhibited between the composite particles of soap and oil.

A

Dispersion forces. The (uneven distribution of electrons produces) weak, temporary dipoles formed along the hydrocarbon chain of soap are mutually attracted to the similarly formed weak temporary
dipoles formed along the oil molecules

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3
Q

Name and explain the origin of the predominant attractive force exhibited between the composite particles of soap and water.

A

Ion-dipole. The negative charge on the carboxylate ion at the end of the soap
structure is mutually attracted to the positive end of the hydrogen-oxygen dipole of the water
molecule.

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4
Q

What forces are broken when soap molecule dissolved in water.?

A

Broken: The ionic bonds between the metal cation and the organic anion, dispersion forces between molecules of soap

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5
Q

What intermolecular forces are formed when a soap molecule dissolves in water?

A

Formed: ion-dipole forces between the anions and cations from the dissociated soap molecule, dispersion forces between non-polar portion of anion and water

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6
Q

What intermolecular forces are broken when a group of soap molecules form a micelle?

A

Broken: dispersion forces between non-polar portion of anion and water

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7
Q

What intermolecular forces are broken when a group of soap molecules form a micelle?

A

Dispersion forces between non-polar portions of anions

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8
Q

What intermolecular forces are formed when grease is removed from clothing?

A

Dispersion forces between the grease and the fabric

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9
Q

What intermolecular forces are broken when grease is removed from clothing?

A

Dispersion forces between grease and micelles

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10
Q

What is a soap?

A

long hydrocarbon chain attached to a charged end.

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11
Q

Where are saturated fats usually found?

A

plant or animal sources, existing as solids at room temp

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12
Q

Where are monounsaturated fats usually found?

A

Olive oil, canola oil and palm oil are common plant oils, existing as liquids at room temperature

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13
Q

What is the structure of fats and oils?

A

They contain non-polar molecules known as triglycerides

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14
Q

Why are fats and oils insoluble in water

A

are unable to form hydrogen bonds with water, therefore are insoluble in water

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15
Q

How are triglycerides synthesised?

A

Condensation reaction between glycerol molecule and three fatty acids, which is a esterification reaction

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16
Q

What are fatty acids?

A

carboxylic acids with chain lengths of eight or more carbon atoms.
- carboxyl group is attached o a long unbranched hydrocarbon chain or ‘tail’

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17
Q

What is the glycerol?

A

propane-1,2,3-triol is relatively small molecule with three hydroxyl functional groups

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18
Q

How does the condensation reaction to form triglyceride occur? (2)

A
  • Triglyceride is produced by a condensation reaction that carboxyl group of a fatty acid and a hydroxyl group of glycerol, forming an ester link.
  • three ester links form as one glycerol molecule and three fatty acids react, also forming three molecules of water
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19
Q

What are saturated fatty acids?

A

Contain only single carbon-carbon bonds

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20
Q

What are monounsaturated fatty acids?

A

contain one carbon-carbon double bond in their hydrocarbon chain

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21
Q

What are polyunsaturated fatty acids?

A

contain more than one carbon-carbon double bond

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22
Q

What are polyunsaturated fatty acids usually found?

A

Fish and vegetable oils, Linoleum acid (CH₃(CH₂)₄CH=CHCH₂CH=CH(CH₂)₇COOH, occurring in sunflower oil

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23
Q

How is soap synthesised?

A

Through saponification/base hydrolysis

24
Q

Describe the process of saponification. (3)

A
  • To synthesise soap from a triglyceride, the ester bonds must be broken through using water
  • the reaction with water is very slow, so a strong base is used (under alkaline conditions)
  • It is a fatty acid ion, combined with the metal ion form the base used for hydrolysis.
25
Q

What are soaps made up of? (3)

A
  • long hydrocarbon chain, which is non-polar.
    eg. in potassium stearate, the hydrocarbon chain is an alkyl group because the hydrocarbon is saturated
  • carboxylate ion (COO⁻) (head of the soap) attached to the hydrocarbon tail.
    the head is polar as there is an uneven distribution of charge in this part of the soap.
  • Carboxylate ions are conjugate bases of carboxylic acids.
    eg. in stearate ion is the conjugate base of stearic acid
    Metal ion, normally Na⁺ or K⁺
26
Q

State the two distinctive parts of a fatty acid used to make soap.

A 
Long hydrocarbon chain (CH3-CH2-CH2-...) 
Carboxyl group (-COOH) or carboxylic acid
27
Q

Describe the process of soap production. (5)

A

high temperatures ensure the hydrolysis of all the oil present.
All oil added is converted to soap and soap is precipitated through the addition of NaCl and then removed filtration.
remaining solution from reaction is removed and glycerol is separated form the basic solution
More oil and hydroxide is being added to vat so that saponification reaction continues
by-product of soap is glycerol

28
Q

What is a limitation of soap?

A

Using it in hard water as when sodium stearate is added to hard water, stearate ions mix with calcium and magnesium ions. Sodium stearate is soluble, calcium and magnesium streets are not and they precipitate as scum.

29
Q

What is hard water?

A

Water supply contains high levels of metal ions such as Ca²⁺ and Mg²⁺

30
Q

What happens when soap is used in hard water? (4)

A

poorly washed clothes
blocked drains from soap scum
grey scum in wash tubs
unsightly stains around basins and taps

31
Q

How can it be soap being used in hard water be fixed? (2)

A

extra soap needs to be used to create an excess of fatty acid ions
- some of the metal ions need to be removed, by adding other negative ions, such as carbonate ions to the soap
carbonate ions soften water by precipitating the magnesium ions.

32
Q

What is one indication of hard water?

A

failure of soap to lather.

33
Q

Do detergents form insoluble slats with calcium ions or magnesium ions?

A

NO

34
Q

What are anionic detergents? (2)

A

active constituent is a negatively charged species.

composed of a sulfonate group attached to a long carbon chain, often via a benzene ring within the structure

35
Q

What are anionic detergents made of?

A

alkyl: non-polar hydrocarbon chain
sulfonate: —SO₃⁻— group which makes a negatively charged end

36
Q

What does the hydrophobic part of the soap do in the process of cleaning?

A

hydrophobic (non-polar) are in the centre of the clump were they are in contact with each other

37
Q

What does the hydrophilic part of the soap do in the process of cleaning?

A

hydrophilic ends are on outer permitter of the clumps where they come in contact with the water

38
Q

What are substances like soaps and detergents called?

A

Surfactants

39
Q

Why is vigorous agitation used?

A

to break up micelles formed by soap

40
Q

How are micelles created? (4)

A
  • non-polar ends of soap particles are the table to position themselves in drops of oil and grass, leaving hydrophilic ends exposed to water
  • water molecules are attracted to polar ends of the soap and oil particle lifts from the fabric, non-polar sections embed themselves around the oil.
  • charged ends of soap protrudes into water, oil surrounded by soap molecules is stable and prevents the stain from reattaching to the fabric
  • when water is drained away the oil drains too
41
Q

How does soap allow it to function as a cleaning agent?

A

exhibits a polar (hydrophilic) end and a long hydrocarbon non-polar (hydrophobic) end. The hydrophobic tail exhibits dispersion forces which interact and successfully embed in the grease or fat. The polar end can interact with the hydrogen bonding in the water molecules. With agitation the soap/detergent molecules are able to break up sections of grease/fat into micelles and cleaning is achieved.

42
Q

What is the similarity between soap and detergent? (chain structure)

A

Soap consists of a large molecular chain with a polar end and non-polar end
Detergent consists of a large molecular chain with a polar end and a non-polar end

43
Q

What is the difference between soap and detergent? (what is it made of)

A

Soaps made from animal fats or vegetable oils.

Detergents are made from organic compounds derived from fossil fuels such as crude oil

44
Q

What is the similarity between soap and detergent? (non-polar end)

A

the non-polar end of the soap molecule attaches to dirt, oil and grease by dispersion forces

the non-polar end of the detergent attaches to dirt, oil and grease by dispersion forces

45
Q

What is one similarity between soap and detergent? (polar end)

A

The polar or ionic end is soluble in water due to hydrogen bonds (or ion-dipole interactions)

46
Q

What is the similarity between soap and detergent? (cleaning action)

A

Soap and detergent molecules bury themselves in oil, grease or dirt and form micelles that are dispersed throughout the water

47
Q

What is the difference between soap and detergent? (charge)

A

Soaps are anionic (negatively charged) and have -COO- as their polar end
Detergents can be anionic, cationic (positively charged) or neutral. Those that are anionic often have a -SO3- end.

48
Q

What is the difference between soap and detergent? (form scum?)

A

Soaps form an insoluble scum with hard water. They do not clean well in hard water.
Detergents are soluble in the presence of the ions in hard water and can still perform their cleaning function satisfactorily.

49
Q

What differences would you expect between a soap made with a saturated fat and a soap made with unsaturated fat? (4)

A

Unsaturated soap molecules occupy more space than saturated due to the double bond.
The effectiveness of a unsaturated soap is worse than saturated due to the weaker dispersion forces due the chains not being able to get close to one another, therefore the soap micelle with not be stable and the soap will be soft or even liquid.
The double bond is more reactive than the single bonds, the soap is more likely to be oxidised to form products that have an unpleasant odour.

50
Q

Compare the cleaning action of detergents with those of soaps.

A

Hydrophobic tails (in both soaps and detergents) exhibit dispersion forces which can interact with grease/fat. The polar ends can interact with hydrogen bonding in the water molecules.

51
Q

What is the equation for the formation of scum?

A

Ca2+ + 2CH3(CH2)16COO- -> (CH3(CH2)16COO)2Ca(s)

52
Q

Why are soap solution basic? (2)

A

The RCOO- is the conjugate base of a weak acid

therefore in the reaction with water it accepts a proton (or it hydrolyses) to produce OH-

53
Q

Biodiesel can be synthesised using a base-catalysed method or a lipase-catalysed method. Outline briefly an argument to justify the use of a lipase-catalysed method rather than a base-catalysed method to produced biodiesel. (yield)

A

Lipase-catalysed method produces a higher yield as it does not produce the soaps that are formed using base-catalysed method

produces a higher purity biodiesel than when the base-catalysed method is used

54
Q

Outline briefly an argument to justify the use of a lipase-catalysed method rather than a base-catalysed method to produced biodiesel. (cost wise)

A

contributes to lower overall costs because:

  • they are less subsequent processing problems than those caused by the presence of a strong base
  • does not add to the expense in the purifying of glycerol as is in the case when in the presence of a strong base
  • it makes it easier seperation of biodiesel from the by-product glycerol
55
Q

Outline briefly an argument to justify the use of a lipase-catalysed method rather than a base-catalysed method to produced biodiesel. (environment)

A

has less negative environmental impact as lipase catalysts are:

  • biodegradable while strong bases aren’t
  • not caustic nor affect acidity of the environment as strong bases do
56
Q

Outline briefly an argument to justify the use of a lipase-catalysed method rather than a base-catalysed method to produced biodiesel. (safety)

A

Is safer as it does not:

  • require the use of caustic materials such as NaOH used in the base-catalysed method
  • produce the high temperatures with its accompanying risks, which a strong base catalyst produces
57
Q

Explain why 300mL of 1.00molL carbonic acid/hydrogencarbonate buffer does not change in pH significantly when 3 drops of 1.00 molL HCL are added , yet when 3 drops of 1.000 Mol HCl are added to 300mL of distilled water there is a significant change in pH

A

As the buffer system is high in concentration of the weak acid of carbonic acid, when it reacts with the HCl it does not change the pH significantly as it is able to use it up as the buffer system is at equilibrium the equilibrium will simply shift to conteract this change. While when HCl is add to distilled water which is not at equilibrium or at high concentrations at all it cannot conteract the decrease in pH and because of this there will be a significant change as distlled water as isn’t a weak acid or base as it is neutral.

  • the HCl increases the concentration of H3O+ ions
  • while water cannot act as a buffer system as in water there is insuffiecient OH- to react with the added H3O+ so all the added H3O+ contribuites to the sifniciant change in pH.

MECH U3/4 (8 decks)

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