post lab discussion: exp. 4 Flashcards
saponification
carboxylate salts with very long hydrocarbon chains
made from base hydrolysis of a fat or an oil (made of TG - ester of fatty acids)
how are soaps traditionally made
animal fat and lye (NaOH)
what happens when esters are treated with NaOH
converted into carboxylate salts which upon neutralization yield carboxylic acids
- the base NaOH breaks the ester bond in the fat
what base is usually used in saponification
NaOH or KOH
they are used for hydrolysis
FA are deprotonated (lose H atoms due to the base NaOH or KOH)
a sodium or potassium ion attached
hence they can become charged, they can dissolve in water (more soluble)
it has a long nonpolar tail, they are also compatible with nonpolar greases and oils.
carboxylate salts
a common soap ingredient
Sodium palmitate
- has 16 C chain
- 1 Na and O atom (water loving)
true or false:
saponification under basic conditions is reversible
false - irreversible
how are soaps are able to emulsify fats and oils
by forming micelles
- E=enough soap molecules surrounding the oil droplets facilitate the dispersion of the oil droplets in water where they can be easily washed away.
what are the methods of breaking down fat or oil molecules
- Using lots of soap:
could accommodate more fat molecules - Using hot water:
can melt solid fats - Agitation:
breaks down fats and oils into smaller droplets
fats and oils
triesters of glycerol and three fatty acids
- fats, oils and FA r generally insoluble in water bcs of the presence of long hydrophobic tails
methodology
Soap preparation (coconut oil + 15ml EtOH + 15ml 20% NaOH + heating & stirring + 50ml 30% NaCl solution)
Vacuum filtration
Comparison to distilled water (negative control) and commercial soap (positive control)
negative control vs positive control
Negative Control (Distilled Water):
A negative control shows what happens when there is NO effect
Distilled water has no cleaning/soap properties
It serves as a baseline to show what “no soap activity” looks like
If your experiment works, your soap should perform better than plain water
Positive Control (Commercial Soap):
A positive control shows what a KNOWN working example looks like
Commercial soap is a proven, working soap
It shows what successful soap activity should look like
It lets you compare how well your homemade soap works compared to a known good soap
This helps you determine if your soap preparation was successful by comparing it to both:
Should work better than distilled water (negative)
Should work similarly to commercial soap (positive)
formation of negative pressure at the outlet of the filtrate and using it as the driving force of filtration
vacuum filtration
what is the use of the vacuum filtration
to obtain a filter residue with low moisture content
what is the expected result after the soap soln is subjected to vacuum filtration
formation of white solid clumps with little to no moisture
however,
Some soap samples hardened or formed solid clumps as soon as 50ml of 30% NaCl solution was added, but some soap samples remained liquid even after the ice bath.
what are the possible source of errors during the experiment
too much coconut oil was added
a portion of the NaOH soln was not dispensed properly (not adding the right amt)
inadequate mixing
how long is the curinng time for soaps
for around 4 weeks where the soap lose more water and become milder
(some become physically harder and longer lasting)
what is the expected pH level
that ranges from pH 7 to 10
- soaps that have a pH level greater than 10 are considered lye-heavy
- can irritate or burn the skin
factors to consider:
Saponification reaction takes around 24 hours and continues to become milder with time.
what is expected when shaking the soap mixed with water
that the soap becomes colloidal (these particles float around evenly) in nature
agitating
comparison of the foaming capacity of the soap samples is usually based on
the height of the foam created after agitation
Taller foam = stronger soap action
Shorter foam = weaker soap action
substances that reduce the surface tension in the liquid
surfactant
Soap reduces the surface tension of the water, making the water molecules less likely to stick together and more likely to interact with oil or grease.
soap interaction with oil
hydrophilic part:
interact with the water molecules in solution, forming the outer surface of the micelle
hydrophobic part:
interacts with the oil, trapping the oil in the center
[As the soapy water is rinsed away, the oil/grease goes along
with it.]
hard water test
hard water:
water that contains a significant concentration of Mg2+ and Ca2+ ions.
these ions form precipitates with soap molecules which is often characterized as a gray line on a bathtub or sink called “soap scum”
soft water:
water that contains very few or no ions that precipitate with soap
more soap molecules are available in solution that can interact with oil molecules, making soaps much more effective in soft water than
in hard water
[soaps are less effective in hard water]
what happens as the soap molecules form precipitates with these ions, most of the soap molecules are no longer present in solution.
less emulsification capacity lass foam formed
