Two identical 732.0-L tanks each contain 212.0 g of gas at 293 K, with neon in one tank and nitrogen in the other. Based on the assumptions of kinetic–molecular theory, rank the gases from low to high for each of the following properties.

(a) Average speed

Video transcript

Welcome back everyone. At 293 Kelvin, two identical 750 L tanks each hold 115 g of gas with one tank containing helium and the other methane based on kinetic molecular theory, which gas has a faster average speed. For the purposes of this problem, we can recall that the average speed. A big gas is calculated as square root of eight RT divided by pi M. Now R is the universal gas constant tea is temperature. It's the same right for each gas and therefore the only variable that is different is the molar mass. First of all, we understand that we don't need volume, we don't need temperature because it's the same for comparison. And we definitely don't need to use mass because it's not part of the formula according to the formula. The average speed is inversely proportional to one divided by square root of M. Actually, it's inversely proportional to the square root of molar mass that would be more accurate to say right. So the lower the molar mass, the higher the average speed. So let's compare our molar masses starting with helium, the molar mass of helium based on the periodic table is 4 g per mole. And for methane is composed of carbon and four hydrogens, we essentially get a molar mass of 16.04 g per mole. If we're looking for the faster average speed, we're interested in the lower molar mass, which essentially corresponds to helium. And the answer is helium, it would have a faster average speed because helium has a lower molar mass than methane. Thank you for watching.