If 4.0 g of O2 (g) and 4.0 g of He (g) are placed in a 5.0-L vessel at 65 °C, what will be the partial pressure of each gas and the total pressure in the vessel?,

Mass of O2 = 4 g, converting to moles = 4 g / 32 g/mol = 0.125 mol

Mass of He = 4 g, converting to moles = 4 g / 4 g/mol = 1 mol

Temperature T = 65 + 273 = 338

Volume of the vessel V = 5 L

Universal Gas constant R = 0.08206 L atm / mol K, Pressure by O2 in vessel P1 = nRT / V = 0.125 x 0.08206 x 338 / 5 = 0.69

atm

Pressure by He in vessel P2 = nRT / V = 1 x 0.08206 x 338 / 5 = 5.55 atmTotal pressure = 0.69 + 5.55 = 6.24 atm