How does molecular weight affect the rate of diffusion? | Socratic
Diffusion is the movement of particles from where they are more concentrated to The average kinetic energy of a particle (KE) gives us the. Molecular weight is how much mass each particle has (how heavy it is). The heavier the particle, the slower it is going to move (assuming. Molecular weight is indirectly proportional to the rate of diffusion: the smaller, The rate of diffusion has a direct relationship with the concentration gradient.
In this regard, the study aimed to determine the effect of molecular weight on the rate of diffusion of substances. The specific objectives were: The tube test was initiated with the preparation of the set-up which was a two-feet glass tube placed horizontally to a pair of stand and locked with a clip.
Two cotton balls of the same size were dipped slightly, thoroughly and simultaneously to a hydrochloric acid HCl and the other to an ammonium hydroxide NH 4OH.
Immediately, the two cotton balls were plugged simultaneously to both ends of the glass tube as shown in Figure 1. The point where the cotton balls were plugged was then marked. Glass Tube Set-up School Science Lessons, After a white ring of smoke appeared inside the glass tube, the point where it was seen was marked.
The distance from each initiation point of the cotton balls to the point where the smoke appeared was measured using a ruler. The same procedure was done by the 4 groups and data were gathered.
Graham's law - Wikipedia
The total distance was calculated by adding the distances of the two substances from each initial point. The ratio of the distance of each substance to the total distance was also computed as well as the ratio of one substance to the other and its average. Agar-water gel setup One drop of potassium permanganate KMnO4potassium dichromate K2Cr2O7 and methylene blue was simultaneously placed to each of the three wells in the agar-water gel.
Immediately, the petri dish was covered and the diameter of each colored area of the well was measured using a ruler, excluding the stains around it. The measured diameter was recorded for zero minute.
After five minutes, the diameter of each well was again measured and recorded for five minutes. The same recording was done with a regular interval of five minutes until reaching 25 minutes.
The relationship of molecular weight of substances to its average rate of diffusion and relationship of time to the partial rates of diffusion of substances were presented through a graph as shown in Figures 3 and 4. The white ring of smoke, as said on the introduction of the study, is the result of the reaction between the NH4OH and HCl.
That is, the point where the molecules of the two substances met and formed a solid product. Computing the average distance of the two substances, still, the distance between the cotton-soaked-in-HCl and the smoke Hydrochloric acid, having a molecular weight of Distance of the smoke ring formed by hydrochloric acid and ammonium hydroxide from each initial point on the glass tube. Trial Distance cm Total Ratio d distance D 1 That hypothesis can be tested using the agar-water gel setup. Agar-water gel setup Table 2 shows the diameter of the wells containing potassium permanganate KMnO4potassium dichromate K2Cr2O7 and methylene blue after 25 minutes with a regular interval of five minutes.
As we can see, on the first five to 15 minutes, KMnO4 had the longest diameter of 10 mm with a net change of from the zero minute. Diameter of potassium permanganate, potassium dichromate and methylene blue on agar-water gel after 25 minutes with a regular interval of 5 minutes. That is, as the time increases, the partial rate of diffusion of all the substances decreases.
Thus, the partial rate of diffusion is generally inversely proportional to the rate of time. Figure 4 is a line graph showing this observed effect of time to the partial rate of diffusion of substances. Figure 3 is a graph showing the relationship between these observed data. Partial rates of diffusion of potassium permanganate, potassium dichromate and methylene blue after 25 minutes with a regular interval of 5 minutes.
Relationship between molecular weight and rate of diffusion?
A graph showing the molecular weights of potassium permanganate, potassium dichromate and methylene blue and their corresponding average rate of diffusion. A graph showing the effect of time to the partial rate of diffusion of the potassium permanganate KMnO4potassium dichromate K2Cr2O7 and methylene blue. Based from the stated data above, the substance with the lowest molecular weight value diffused the fastest and the substance with the highest molecular weight value diffused the slowest.
Three wells in agar-water gel on a petri dish were placed by a drop of potassium permanganate KMnO4potassium dichromate K2Cr2O7 and methylene blue. The diameters of each well were measured in millimeters, excluding the stains surrounding it, within 25 minutes. The data were presented and analyzed carefully.
This process is called diffusion The Holt, Diffusion is the spreading of particles through random motion with the net movements from regions of higher concentration to regions of lower concentration wherein net diffusion can be restated as movement of particles along the concentration gradient. According to Otto and Towle, there are external factors that influence the rate of diffusion of substances. In addition to molecular concentration, two other factors affect the rate at which diffusion occurs.
One of this is temperature. The higher the temperature, the greater the speed of molecular movement. Hence, diffusion occurs from an area of higher temperature to one of lower temperature. Similarly, pressure accelerates molecular movement, resulting in diffusion from a region of higher pressure to one of a lower pressure.
Thus, the differences in molecular concentration, temperature and pressure affect diffusion referring to the force resulting from these differences as diffusion pressure.
Consequently, the study means that the rate of diffusion is inversely proportional to the size of the particle of the substance i. The validity that the molecular weight of a substance has an effect on its rate of diffusion was derivative from the glass tube set-up. At the same manner, the agar-water gel test is used to assess and verify the same matter. This study aimed to determine the effect of molecular weight and time on the rate of diffusion of substances via the glass tube test and agar-water gel test.
The specific objectives were 1. For the first set up, two feet glass tube was fastened horizontally to a ring strand, as shown in Figure 1.
Using fine forceps, two cotton balls of the same size were moistened, one with Figure 1. One end of the tube was then plug with one wet cotton ball and the other end with the other cotton ball.
After some time, a white smoke appeared. The distance of the white smoke to each of the cotton balls was obtained by measuring its length, comparing each measurement and then getting the total distance and average ratio of the diffusion of the substances. A graph comparing the distance of the substances with that of the white smoke was then plotted and analyzed. For the next set up, a petri dish of agar-water gel with three wells was obtained.
The three wells were labeled as follows: Each well was placed with one drop of the prepared solution of each substance. The petri dish was then immediately covered and the diameter in mm. At a regular five-minute interval for thirty minutes, the diameter of the colored area of each substance was measured and recorded, as shown in Figure 3.
A graph comparing the distance of each interval to its original position was also plotted and analyzed. The position of the substances at zero minute. The position of the substances after 30 minutes. Computing for the ratio of the substances by simply getting the proportion of NH 3 and HCl, the average ratio would be 1.
This implies that NH3 have diffused faster than HCl.