# Rate of diffusion and molecular mass relationship

### How does molecular weight affect the rate of diffusion? | Socratic

Diffusion is the movement of particles from where they are more concentrated to where they are less concentrated. The average kinetic energy. The molecular weight of a substance affects its rate of diffusion was procured from rate of diffusion; and 2. to describe the relationship between the molecular . The Relationship between the Molecular Weight, Time and Rate of Diffusion of Substances 1 Maria Pauline Capiroso Group 4 Sec. U – 5L October 14,

In the glass tube test, two cotton plugs with equal sizes were soaked at the same rate to two different substances: The substance NH4OH having a lighter molecular weight diffused faster forming a white smoke. For the agar-water gel set up, three solutions, namely, KMnO4, K2Cr2O7 and methylene blue, were dropped into three different wells in a petri dish of agar-water gel.

Methylene blue displayed the smallest diameter and diffused at the slowest rate because it has the largest molecular weight. Hence, the higher the molecular weight, the slower the rate of diffusion. These molecules move in straight lines until they collide. The force moving these molecules is internal kinetic energy.

The collisions cause the molecules to distribute themselves equally in a given volume. 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.

## Graham's law

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. So the rate of diffusion depends on both of these quantities. Flux and Diffusion The chance of knocking a molecule away from an area is proportional to how many there are in that area. Therefore, more molecules are knocked from areas of high concentration to areas of low concentration than the other way around.

The rate at which molecules flow in a certain direction is called the flux. As a result of the random redistribution, the flux is proportional to both the concentration gradient and a number called the diffusion coefficient, which is a function of both the substance diffusing and what it is diffusing in. The diffusion coefficient characterizes the rate of diffusion. So now I've squared them. And let me actually rearrange it to make it a little bit neater in a new color. So let's do this.

So let me write it out nice and neat. And this is actually going to be Graham's law.

So all I'm doing is rearranging the formula. I've got rate 1. This is the diffusion rate of one molecule divided by the diffusion rate of a second molecule, and then the molecular weight on the other side of the second molecule divided by the molecular weight of the first molecule.

And you do a square root of this side. So, that's just a rearrangement of the formula. But what I've written out for you is now Graham's law. It's basically taking the kinetic energy rule and rearranging it to make sense for molecules. And let me make a little bit of space here.

And so that an extension of this would be if you're just thinking about one molecule, then the rate, the diffusion rate-- when I say rate I mean diffusion rate-- is going to be proportional to the square root of the molecular weight. So, let's figure out how to apply this to our little riddle.

### Graham's law - Wikipedia

We wanted to know whether oxygen or carbon monoxide is going to diffuse faster. And I can now go back to our the periodic table and look up oxygen. And I know that the molecular weight of 16 here and carbon is And that means that O2 is just 16 times 2.

So the molecular weight is And carbon dioxide is going to be 2 oxygens plus 12 more. So it's going to be So these are the molecular weights of carbon dioxide and oxygen. So basically what I do is I just plug them in. And I say, OK, let's plug them into the formula. Let's use this one right here. And I'm going to call rate 1 my oxygen rate.

So what's happening with rate 1? We'll say, well, rate 1 is rate of oxygen-- I'm going to write a big o here-- equals the square root of-- let's make sure I stay consistent-- I said 1 was oxygen, so it's going to be 32 down here and 44 up here.

And then that's going to be multiplied by rate of carbon dioxide. And I'll put a c for carbon dioxide.

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

So what does this work out to be? I just punched it into the calculator. So really, the diffusion rate of oxygen is 1. So that's our answer. The oxygen is going to be the winner.

So it's going to move faster. This is going to move a little bit faster. And it's going to get to our alien friend's nose first. So this is the power of Graham's law.