# Molecular weight and rate of diffusion relationship

### Why Does the Rate of Diffusion Vary With Molecular Weight & Temperature? | Education - Seattle PI

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. Methylene blue, with the largest molecular weight, had the smallest diameter ( mm) and had the slowest diffusion rate ( mm/min). Thus, the larger the. The rate of diffusion (Urms) is given by: Urms=√3RTMM. Where MM is the molar mass of the gas. Thus, when MM increases, the diffusion rate.

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.

### Graham's law - Wikipedia

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.

- What is the relationship between molecular weight and rate of diffusion?
- Why Does the Rate of Diffusion Vary With Molecular Weight & Temperature?
- How does molecular weight affect the rate of diffusion?

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. A graph showing the molecular weights of potassium permanganate, potassium dichromate and methylene blue and their corresponding average rate of diffusion.

## Graham's law

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. In conclusion, the molecular weight of a substance is inversely related to its rate of diffusion. However, personal errors may have been occurred during the conduct of the study due to carelessness, poor technique in measurements or wrong measurements of the experimenters. Thus, further experimentation is needed in order for the study to be validated.

Diffusion, Mass Transfer in Fluid Systems 2nd ed. The mean free path is directly proportional to the temperature of the gas, and the average velocity is proportional to the square root of the temperature divided by the square root of the molecular weight.

### The Effect of Molecular Weight to the Rate of Diffusion of Substances | Angel Ombid - gtfd.info

Diffusion in liquids balances the osmotic pressure resulting from concentration gradients with the viscous force that impedes the flux. The osmotic pressure is proportional to the temperature, and the viscous force is proportional to the viscosity of the fluid and the diameter of the diffusing molecule.

Consequently, diffusion coefficients in liquids are directly proportional to the temperature of the fluid but do not depend on the molecular weight of the substance diffusing. Diffusion Across Membranes Effusion, a process similar to diffusion, occurs when gas molecules escape through a small hole. If the hole is very small, then a molecule experiences few collisions as it flows through. One end of the tube was then plug with one wet cotton ball and the other end with the other cotton ball.

## Relationship between molecular weight and rate of diffusion?

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. Since the gaseous molecules of NH3 diffused at a faster rate, it reached the opposite side of the glass tube reacting with HCl wherein the white smoke formed. As shown in Table 2, a record of the measurements of the diameter of the substances per interval was recorded and was analyzed. Distance of each substances from each well per interval. Then, the average of the computed partial rates of each substance was obtained to get the average rate of diffusion.

Showing that KMnO 4 diffused faster that the other substances. Methylene blue, having the highest molecular weight diffused slower in respect with the other substances.