The Effect of Molecular Weight on the Rate of Diffusion of Substances
ABSTRACT
The effect of molecular weight on the rate of diffusion was measured using two tests namely: the glass tube test and the agar-water test. The set-up of the glass tube test used two cotton balls of the same size. One cotton ball is moistened with hydrochloric acid (HCl) and the other one is moistened with ammonium hydroxide (NH4OH). The two cotton balls were inserted in both ends of the glass tube. NH4OH which has a lighter molecular weight (35.0459 g/mole) diffused with a faster rate (dave=20.25cm) as compared to HCl which has a greater molecular weight (36.4611g/mole) and diffused with dave=16.38 cm. A white ring of smoke formed closer to the heavier substance. The agar-water gel set-up used a petri-dish of agar-water gel with three wells on it. A drop of potassium permanganate (KMnO4) was put on one well, a drop of potassium dichromate (K2Cr2O7) was put on the other and a drop of methylene blue was put on the third well. Methylene blue which has the heaviest molecular weight of 374 g/mole occupied a small diameter of colored area which is 11mm. and had the slowest rate of diffusion which is 0.613 mm/min. Thus the lighter the molecular weight, the faster is the rate of diffusion.
INTRODUCTION
As we open a household ammonia it will not take that long before the smell of it occupies the whole room. The gaseous molecules travel quickly and mix with the molecules in the air which makes it possible for people to immediately smell the ammonia as soon as it is opened. Such process is known to be the diffusion (Myers, Oldham and Tocci, 2006). Gases tend to diffuse rapidly with each other. It does not matter even if the air in a particular place is still because it will just take some minutes before the ammonia molecules occupy the place. During the process of diffusion, the substance moves from an area of higher concentration to an area of lower concentration.
According to Myers, Oldham and Tocci (2006), particles of low mass diffuse faster than particles
The effect of molecular weight on the rate of diffusion was measured using two tests namely: the glass tube test and the agar-water test. The set-up of the glass tube test used two cotton balls of the same size. One cotton ball is moistened with hydrochloric acid (HCl) and the other one is moistened with ammonium hydroxide (NH4OH). The two cotton balls were inserted in both ends of the glass tube. NH4OH which has a lighter molecular weight (35.0459 g/mole) diffused with a faster rate (dave=20.25cm) as compared to HCl which has a greater molecular weight (36.4611g/mole) and diffused with dave=16.38 cm. A white ring of smoke formed closer to the heavier substance. The agar-water gel set-up used a petri-dish of agar-water gel with three wells on it. A drop of potassium permanganate (KMnO4) was put on one well, a drop of potassium dichromate (K2Cr2O7) was put on the other and a drop of methylene blue was put on the third well. Methylene blue which has the heaviest molecular weight of 374 g/mole occupied a small diameter of colored area which is 11mm. and had the slowest rate of diffusion which is 0.613 mm/min. Thus the lighter the molecular weight, the faster is the rate of diffusion.
INTRODUCTION
As we open a household ammonia it will not take that long before the smell of it occupies the whole room. The gaseous molecules travel quickly and mix with the molecules in the air which makes it possible for people to immediately smell the ammonia as soon as it is opened. Such process is known to be the diffusion (Myers, Oldham and Tocci, 2006). Gases tend to diffuse rapidly with each other. It does not matter even if the air in a particular place is still because it will just take some minutes before the ammonia molecules occupy the place. During the process of diffusion, the substance moves from an area of higher concentration to an area of lower concentration.
According to Myers, Oldham and Tocci (2006), particles of low mass diffuse faster than particles