Calculate the average molecular weight of air from the data given in Table 10.1.

Video transcript

Hi everyone. This problem reads what is the average molecular weight of moist air? Use the information below. So we're given the components of moist air along with the present volume. And with this information, we want to calculate the average molecular weight. Okay, so with percent volume, this is directly proportional to the number of molecules in the mixture of gasses. So we're going to take this percent volume and turn it into a fraction. Alright, so for each one we're going to write out its fraction. So for nitrogen gas the fraction is 0. for oxygen gas, it's 0.20943. For argon gas it's 0.934. For carbon dioxide It is 0. and four H20. It is 0. 06. Okay, so we took the percent volume and turned them into fractions now to calculate the average molecular weight. We're going to also need the molar mass of each of these gasses. Okay, so let's go ahead and write moller mass. Okay, so we're going to go ahead and go down the list. So, for nitrogen gas it is 28. g per mole for oxygen gas, it is 32 g per mole for argon gas. It is 39. g per mole for carbon dioxide, 44.1 g per mole and H 20 is 18.16 g per mole. So now we have all the information that we need to calculate the average molecular wait, so the average molecular weight is going to equal the sum of the fractions times its molar mass. Okay, so for all of them, and we're going to take the sum. So it's going to be the fraction times the molar mass for each. Alright, so let's go ahead and get started. So We're going to start here. So for nitrogen gas, our fraction is 0. times its molar mass 0.2 grams per mole plus the fraction for oxygen gas 0.20948 times its molar mass 32 g per mole plus the mole fraction of argon. So 0. times Its smaller mass, .948 grams per mole. Running out of room plus for carbon dioxide, its fraction is 0.37 times its molar mass 44.1 g per mole Plus H 20. So it's fraction is 0. times Its molar mass 18.01 six g per so we'll just pretend all of this is on one line because we're just taking the sum of everything. And so our final answer, once we take the sum we're gonna write average molecular wait, Let's go ahead and move this over the average molecular weight. Once we do the calculation is going to equal 28.97 g per mole. So this is the average molecular weight of the moist air, using the information that was given in the table. Okay, so that is it for this problem. I hope this was helpful.