The Earth's atmosphere has a mass of approximately 5.15 * 1015 kg. If the average molar mass of air is 28.8 g/mol, how many moles of gas make up the atmosphere? What is the volume of the atmosphere in liters under conditions of STP? (Note: The average molar mass of air is the weighted average of the molar mass of nitrogen and oxygen. 0.20132.0 g>mol2 + 0.80128.0 g>mol2 = 28.8 g>mol.)

Video transcript

Hey everyone, Let's check out this problem at S. T. P. What is the volume occupied by 33.5 g of argon gas. Now remember STP stands for standard temperature and pressure and our standard temperature is equal to 273.15 kelvin And our standard pressure is equal to 180 M. The equation that we're going to need to use to solve this problem is our ideal gas equation which is PV equals N R. T. And then the problem they are asking us what is the volume. So here we're solving for our volume. And when we isolate that variable, we get volume is equal to N. R. T over peak. So let's go ahead. Go ahead and plug in what we know We know that N represents moles. And here they give us 33.5 g of argon gas. So let's go ahead and convert that g to moles. Using our molar mass And one mole of Argon. We have 39. five g of Oregon. Our g of argon cancel. And we're left with moles. And when we do that calculation, we get 0.838 moles of argon. So we'll go ahead and plug that in 0.838 moles of bargain RR represents our gas constant which is 0. 206 leaders atmosphere over malls Calvin. And our temperature is that standard temperature of 273.15 Kelvin and this is all over pressure And our standard pressure is 180 M. So let's just make sure our units cancel here are most of Argon cancel our A. T. M. Cancels and our kelvin cancels. So the unit that we're left with is volume, which is perfect. When we do this calculation, we get a volume of 18.7 leaders and this is answer choice B. Alright, everyone. That's the end of this problem. I hope this was helpful.