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

All the elements are arranged by melting points on the periodic table. in row they go from metals to gasses. in the row from sodium to argon, sodium is more reactive than the one on its right, magnesium.