Diffusion
The Effect of Molecular Weight and Time on the Diffusion Rate of Potassium Permanganate, Potassium Dichromate, and Methylene Blue.1
Arantxa Alex Carpio
Group 1 Sec. X – 4L
March 24, 2015
ABSTRACT
The effect of molecular weight and time on the rate of diffusion was determined using the agar-water gel test. A petri dish of agar-water gel with three wells was prepared and a prepared solution of each substance was dropped on each well; one with potassium permanganate (KMnO4), the other with potassium dichromate (K2Cr2O7), and the last one with methylene blue. The average diameter of potassium permanganate (11.64 mm) was bigger than potassium dichromate (9.18 mm) and methylene blue (7.91 mm). Note that the molecular weight of potassium permanganate is 158g/mole, potassium dichromate is 294 g/mole and methylene blue is 374 g/mole. Thus, the lighter the molecular weight, the faster the rate of diffusion.
INTRODUCTION
Diffusion is the process in which the molecules merge as an outcome of their spontaneous movement or randomized motion of kinetic energy. It is when two chemical species react together at every encounter (combining or merging of the two species for a number of subsequent collisions in solution) and chemical change take place as fast as the reactants can diffuse together (Reichardt, 1988). It may occur in solids, liquids, or gasses. It depends on many factors like temperature, molecular weight, concentration of molecules in the surrounding gas and the size of the space in which the gas diffuses (Abrash and Hardcastle, 1981). According to Crank and Park (1968), another factor that affects the diffusion in gas is the nature of the gas.
Diffusion offers the clearest evidence for molecular migration in a liquid because it shows the freedom of molecules to move in liquid. Liquid diffusion is slower than gas diffusion because gas molecules are far apart and collisions between them are rare, causing them to diffuse rapidly. Liquid
Arantxa Alex Carpio
Group 1 Sec. X – 4L
March 24, 2015
ABSTRACT
The effect of molecular weight and time on the rate of diffusion was determined using the agar-water gel test. A petri dish of agar-water gel with three wells was prepared and a prepared solution of each substance was dropped on each well; one with potassium permanganate (KMnO4), the other with potassium dichromate (K2Cr2O7), and the last one with methylene blue. The average diameter of potassium permanganate (11.64 mm) was bigger than potassium dichromate (9.18 mm) and methylene blue (7.91 mm). Note that the molecular weight of potassium permanganate is 158g/mole, potassium dichromate is 294 g/mole and methylene blue is 374 g/mole. Thus, the lighter the molecular weight, the faster the rate of diffusion.
INTRODUCTION
Diffusion is the process in which the molecules merge as an outcome of their spontaneous movement or randomized motion of kinetic energy. It is when two chemical species react together at every encounter (combining or merging of the two species for a number of subsequent collisions in solution) and chemical change take place as fast as the reactants can diffuse together (Reichardt, 1988). It may occur in solids, liquids, or gasses. It depends on many factors like temperature, molecular weight, concentration of molecules in the surrounding gas and the size of the space in which the gas diffuses (Abrash and Hardcastle, 1981). According to Crank and Park (1968), another factor that affects the diffusion in gas is the nature of the gas.
Diffusion offers the clearest evidence for molecular migration in a liquid because it shows the freedom of molecules to move in liquid. Liquid diffusion is slower than gas diffusion because gas molecules are far apart and collisions between them are rare, causing them to diffuse rapidly. Liquid
Cited: Abrash, H.I. and K.I Hardcastle. 1981. Chemistry. New Jersey: Prentice Hall. p. 67, 236. Reichardt, C. 1988. Solvents and Solvent Effects in Organic Chemistry. 2nd ed. New York: VCH Publishers. pp. 270-271. Crank, J. and G.S. Park. 1968. Diffusion in Polymers. New York: Academic Press Inc. pp. 50-51.