A 12.5-L scuba diving tank contains a helium–oxygen (heliox) mixture made up of 24.2 g of He and 4.32 g of O₂ at 298 K. Calculate the mole fraction and partial pressure of each component in the mixture and the total pressure of the mixture.

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SORT The problem gives the masses of two gases in a mixture and the volume and temperature of the mixture. You are to find the mole fraction and partial pressure of each component, as well as the total pressure. STRATEGIZE The conceptual plan has several parts. To calculate the mole fraction of each component, you must first find the number of moles of each component. Therefore, in the first part of the conceptual plan, convert the masses to moles using the molar masses. In the second part, calculate the mole fraction of each com- ponent using the mole fraction definition. To calculate partial pressures, calculate the total pressure and then use the mole fractions from the previous part to calcu- late the partial pressures. Calculate the total pressure from the sum of the moles of both components. (Alternatively, you can calculate the partial pressures of the components individually, using the number of moles of each component. Then you can sum them to obtain the total pressure.) Last, use the mole fractions of each component and the total pressure to calculate the partial pressure of each component. GIVEN: MHe = 24.2 g, mo₂ = 4.32 g, V = 12.5 L, T = 298 K FIND: XHe> XO₂ PHe› Po₂) Ptotal CONCEPTUAL PLAN mHe 1 mol He 4.00 g He XHe nHe 9 XO₂ nHe nHe + no₂ (nHe + no₂) RT Ptotal = V PHe XHEPtotal; Po₂ = XO₂Ptotal Pa = XaPtotal mo₂ no₂ nHe + no₂ RELATIONSHIPS USED Xa na/ntotal (mole fraction definition) Ptotal V = totalRT 1 mol O₂ 32.00 g 0₂ no₂