Suppose that on another planet the atmosphere consists of 17% Kr, 38% CH4, and 45% O2. What is the average molar mass at the surface? What is the average molar mass at an altitude at which all the O2 is photodissociated?

Video transcript

Hey everyone, we're told that the atmosphere of a new planet was discovered to compose 21% neon, 43% argon and 36% hydrogen were asked to calculate the molar mass at the surface of the planet and to calculate the molar mass when all of the hydrogen has been broken down. Starting off with question # one we can go ahead and convert those percentages into its decimal form and multiply each one by its respective molar mass. So setting this up, we have our average molar mass and we're going to multiply 0.21 by neons molar mass of 20.18 g per mole, which can be found in our periodic table. Then we're going to add 0. Times the molar mass of Argon, which is 39.95 g per mole. Lastly we're going to add 0. times the molar mass of our hydrogen, which is 2.02 g per mole. Now, when we calculate this out, we end up with a molar mass of 22.1435 g per mole. And since we only have two significant figures, our answer is going to be 22 g per mole. Now, let's move on to our second question or asked to calculate the molar mass when all the hydrogen has broken down. So since we're talking about the dissociation of hydrogen, This means that we will have to 0.36 fractions of hydrogen atoms. So our total fractions is going to come up to 0.21 plus 0.43 plus 0.36 plus 0.36. Since now we have 20.36 fractions. And in total we get 1.36. Now to find our molar mass, we're going to do the same steps as we did earlier And we're going to multiply 0. Times 20.18 g per mole of neon. And we're going to add on 0.4, three times 39.95 g per mole of our argon. Next, we're going to add 0.72 which is our 0.36 times two. And we're going to multiply it by 1. grams per mole of our hydrogen. And this is going to be all divided by Our total fractions which is 1.36. So when we calculate this out, we end up with 16.28 g per mole. And again, since we only have two significant figures, we can round this down to 16 g per mole. And these are going to be our final answers. Now, I hope that made sense. And let us know if you have any questions