How Is Oleic Acid Estimated?
The estimation of enormous distances is simple. We realize very well how to magnify. We use kilometers for terrestrial applications, light years for a long time for heavenly applications, and 1 parsec (3.26 light-years) for galactic applications. On the opposite end of the scale, we have a little measure. We can get millimeters and our naked eyes can see up to 0.1 mm however after that it is extremely difficult to imagine.
(image will be uploaded soon)
An electron magnifying lens is a microscope that enlightens the sample with light emission electrons. This permits the electron microscope to concentrate pointedly on a little item, for example, an atom. This electron can be made to have a short frequency, right around multiple times shorter than the visible light, along these lines giving the electron microscope a better resolution than an optical magnifying instrument. A transmission electron magnifying instrument can accomplish superior to 50 Picometer (10-12) resolution and you ought to remember that atoms range from 30 – 300 Pico meters.
Prior to the innovative progressions, however, we just had a rough estimate of the size of the atom. Let's examine a few of the methods or techniques now.
Oleic Acid: Thin Film Method
The particles/molecules of oleic acid and other such vegetable oils have a place with a classification called lipids. These are normally called 'fat particles/molecules '. Their structure is hydrophobic, which implies that they are inadequately dissolvable in water. Molecules that can be dissolved in water are called hydrophilic. The word originates from the Greek term signifying 'water-loving'. Fatty acid molecules, for example, oleic acid are fascinating because they have parts that are hydrophilic and hydrophobic parts.
Image will be uploaded soon
In the image of oleic acid, note that the oleic acid particle/molecule is remaining on the – OH end of the molecule. This was done deliberately in light of the fact that when oleic acid particles/molecules experience water they stand upon it with this end down. Oleic acid buoys on water because of lower thickness. A noteworthy bit of the molecule is hydrophobic. Just the –OH end is hydrophilic.
Since it is so larger than the hydrophilic end, the whole molecule isn't solvent in water. At the point when putting on water, oleic acid molecules will stand up and bolster each other on end in light of attractive forces between the hydrophobic parts of the molecules. If oleic acid is dropped onto water, we make the supposition that it spreads out to a thickness of just a single particle/molecule.
There is a need to dissolve 1 cm3 of oleic acid in 400 cm3 of liquor to get a centralization of 1 part by 400. After that take a big water container and to the surface, we include a uniform layer of lycopodium powder. To this, we include one drop of oleic acid. The drop rapidly extends into a thin, huge circular film of molecular thickness. This is the oleic acid molecules remaining on their hydrophilic ends.
How To Calculate The Thickness Size of A Molecule?
We can quantify the distance across this circle utilizing which we can compute the area 'A'.
Let us assume that the volume of one drop is 'v'
Then,
The volume of n drops is 'nv' for the solution.
So,
The volume of oleic acid in ‘n’ drops of solution = (nv/400) cc
If the area is A cm2 and thickness is ‘t’
Thickness can be calculated as: (with the assumption that the thickness is equivalent to one layer of molecules)
\[A^\ast t=\frac{nv }{400}\]
This implies the thickness is:
Thickness=Volume/Area
\[t=\frac{nv }{A^\ast 400}\]
In light of the assumption that the layer is one molecule thick, we acquire the estimation of the size of the oleic acid molecule. The value of the thickness comes out to be in the order for 10-9 m. Taking into account how basic this exhibition is, this technique has generally excellent precision.
FAQs on Measurement of the Size of Oleic Acid molecule
1. What is the approximate size of an oleic acid molecule as determined by the thin film experiment?
The approximate size (diameter) of an oleic acid molecule is in the order of 10-9 metres. This value is not measured directly but is estimated by creating a monomolecular layer (a film one molecule thick) on a water surface and calculating the film's thickness, which is assumed to be the diameter of a single molecule.
2. What is the fundamental principle behind using the thin film method to measure the size of an oleic acid molecule?
The fundamental principle is to create a film of oleic acid on a water surface that is so thin it is assumed to be only one molecule thick (a monomolecular layer). By knowing the volume of oleic acid used and measuring the area of the film it forms, we can calculate its thickness. This calculated thickness is then taken as an approximation of the diameter of a single oleic acid molecule.
3. Why is oleic acid first dissolved in alcohol before being added to water in this experiment?
Oleic acid is dissolved in alcohol to create a highly dilute solution. This is crucial because it allows us to control and dispense a very small, known volume of oleic acid. Oleic acid itself is a thick oil, and measuring a tiny quantity directly would be impractical. Alcohol acts as a solvent that spreads quickly and then evaporates, leaving behind just the oleic acid to form the thin film on the water's surface.
4. What are the key assumptions made when estimating molecular size using the oleic acid method?
This method relies on several important assumptions to work. The key ones are:
- The film formed on the water surface is a perfect monomolecular layer, meaning it is exactly one molecule thick.
- The oleic acid molecules arrange themselves vertically and are tightly packed, forming a film of uniform thickness without any gaps.
- The drop of solution spreads into a perfectly circular film on the water surface, allowing for an accurate area calculation (A = πr²).
5. What is the formula used to calculate the size (thickness) of the oleic acid molecule in this experiment?
The basic formula is Thickness = Volume / Area. To find the molecular size 't', we use the derived formula: t = (n * v) / (A * C), where:
- t is the thickness of the film (approximating the molecular size).
- n is the number of drops of the solution added to the water.
- v is the volume of a single drop.
- A is the area of the circular film on the water.
- C is the concentration of oleic acid in the alcohol solution (e.g., if 1 cm³ of acid is in 400 cm³ of solution, C = 400).
6. How does the molecular structure of oleic acid help it form a monolayer on water?
The oleic acid molecule is amphiphilic, meaning it has two distinct parts. One end, the carboxyl group (-COOH), is hydrophilic (attracted to water). The other part is a long hydrocarbon chain that is hydrophobic (repels water). When placed on water, the hydrophilic heads dissolve into the water surface while the hydrophobic tails point away from it, forcing the molecules to stand upright and form a stable, single-molecule-thick layer.
7. Why is lycopodium powder sprinkled on the water surface before adding the oleic acid solution?
Lycopodium powder is a very fine, light powder that floats on water. It is sprinkled on the surface to make the boundary of the oleic acid film clearly visible. When a drop of the oleic acid solution is added, it pushes the powder outwards as it spreads, creating a clear circular area. This allows for an accurate measurement of the diameter and, consequently, the area of the film.
8. Why is this method considered an estimation rather than an exact measurement of the molecular size?
This method is considered an estimation because it relies on assumptions that may not be perfectly true in reality. For example, the film might not be a perfect circle, or it might not be a perfectly uniform monomolecular layer. There could be small gaps or areas with more than one layer. These factors, along with potential errors in measuring volume and area, mean the result is a very good approximation of the molecular size, not an exact value.
