A heliox deep-sea diving mixture contains 2.0 g of oxygen to every 98.0 g of helium. What is the partial pressure of oxygen when this mixture is delivered at a total pressure of 8.5 atm?

Video transcript

Hey everyone and welcome back. A Heliox deep sea diving mixture contains 2 g of oxygen to every 98 g of helium. What is the partial pressure of oxygen when this mixture is delivered at a total pressure of 8.5 atmospheres? We are given four answer choices. A 0.53 B 0.022 C 1.8 ND 4.5. They are all given in atmospheres. What we want to do in this problem is first of all, calculate the number of moles of each substance starting with oxygen. We have 2 g of oxygen and the molar mass of oxygen would be 32.00 g per mole. So we essentially want to divide the mass by molar mass to get moles. That's our formula. And we end up with a 0.0625 moles of oxygen. Let's not round it off yet. And now let's calculate the number of moles of helium. We have 98 g and we need to divide that mass by the molar mass of helium which is 4.003 grams promo. Now, in this case, if we calculate the result, we get 24.48 moles. Now, what we want to do from here is remember the Dalton's law of partial pressures. So if we're looking at the partial pressure of oxygen, we need to calculate the mole fraction of oxygen in this mixture, we take 0.0625 moles, which represents the quantity or the amount of oxygen in the mixture. And we need to divide that by the total number of moles in the mixture. We are taking the same number and we are adding the number of moles of helium. Meaning in our denominator, we have the total number of modes of gasses. And in our numerator, we have the number of modes of oxygen. And if we calculate the result here, we essentially get 0.0025 46, that's our mal fraction. And eventually, let's remember that according to the law, partial pressure of a gas. And in this case, our gas of interest is oxygen is equal to the mole fraction of that gas multiplied by the total pressure. So we take the m fraction calculated previously 0.002546. And we multiply by 8.5 atmospheres because that's the total pressure of the mixture. And we get our final answer, that would be 0.022 atmospheres. And this corresponds to the partial pressure of oxygen. Now, if we want to determine the correct answer. That would be option B 0.022 atmospheres. Thank you for watching.