MORE MATHEMATICAL DEFINITION |
It is based on the fact that kinetic energy of gas particle is equal to 1/2 mass of particle time the square of the speed of the gas particle. |
It is based on the fact that kinetic energy of gas particle is equal to 1/2 mass of particle time the square of the speed of the gas particle or: KE = 1/2*m*v2, m = mass of substance, v = speed or velocity of substance and * - multiplication sign. MORE CONCEPTUAL (NON-MATHEMATICAL) DEFINITION |
*So for non-mathematical problems, it is a simple comparison of molar mass (also called Molecular Weight, MW): **Greater MW substance diffuses/effuses SLOWER, lower MW substance diffuses/effuses FASTER. |
Where are basically two type of problems with respect to Graham's Law. One that asks the relative rate of diffusion between two gasses and one that is specifically asking how fast.slow one gas is compared to another gas. |
Example of Conceptual Problem: Which of two substance diffuses Faster (has a higher rate of diffusion), NH3 or H2? Answer: MW of NH3 = 17g/mole and MW of H2 = 2g/mole, then H2 diffuses FASTER since it has the lower MW. For More Mathematical problems There are basically two type of problems with respect to Graham's Law. One that asks the relative rate of diffusion between two gasses and one that is specifically asking how fast.slow one gas is compared to another gas. |
*Example of Relative Rate of Gas Diffusion Problems *Expected Work for Relative Rate of Gas Diffusion Problems *You Tube Video of Expected Work for Relative Rate of Gas Diffusion Problems |
*Example of Specific Rate of Gas Diffusion Problems *Expected Work for Relative Specific Rate of Gas Diffusion Problems *You Tube Video of Expected Work for Specific Rate of Gas Diffusion Problems |
If you only want to remember one way that works all the time for both types of these problems, then always put the first gas in the problem in the numerator and the second gas in the denominator or rfirst gas / rsecond gas. |
The easiest way of doing these problems is to always put the first gas in the problem in the numerator and the second gas in the denominator or rfirst gas / rsecond gas. |