You have been assigned the task of measuring the equilibrium constant for the reaction N2O4 2NO2 as a function of temperature. To do so, you obtain a rigid 2-liter vessel equipped with a pressure gauge evacuate and then fill the vessel with a mixture of NO2 and N204, and heat the vessel to T0 = 473 K, a temperature at which you know the gas is essentially pure NO2. The gauge pressure at this point is noted to be 1.00 atm. You then decrease the temperature in stages, recording the equilibrium gauge pressure at each temperature. The data are as follows:
(a) How many gram-moles of NO2 are in the vessel at 473 K?
(b) The reaction equilibrium constant is Kp = P2NO2 / PN2O4 where and PN2O4 are the equilibrium partial pressures of NO2 and N2O4. Derive an equation or a series of equations for calculating Kp (atm) from specified values of T and P gauge. (Suggestion: Begin by defining a1 and n2 as the moles of NO2 and N2O4 present at equilibrium.) Then calculate Kp for T = 350 K, 335 K. 315 K, and 300 K. (Suggestion: Use a spreadsheet program.)
(c) The equilibrium constant should vary with temperature according to the relation Kp = ae-b/T use the results of part (b) to determine the values of a and b by a graphical curve-fitting procedure. [Suggestion: Use the spreadsheet program from part (b).]