Step1 Moles of He = 50/4.0026 Step2 Moles of Xe = 50/131.29 Step3 Find total moles Step4 Partial pressure of He=[ Moles of He/Total moles] x750 torr Step5 Partial pressure of Xe = 750 - partial pressure of He Solution Step1 Moles of He = 50/4.0026 Step2 Moles of Xe = 50/131.29 Step3 Find total moles Step4 Partial pressure of He=[ Moles of He/Total moles] x750 torr Step5 Partial pressure of Xe = 750 - partial pressure of He.