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 evacuate a rigid 2-liter vessel equipped with a pressure gauge, fill the vessel with a mixture of NO₂ and N₂O₄, and then heat it to T0 ˆ 473 K, a temperature at which you know the gas is essentially pure NO_2. 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

where p_NO2 and p_N2O4 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 Pgauge. (Suggestion: Begin by defining n1 and n2 as the moles of NO₂ and N₂O₄ present at equilibrium.) Then calculate Kp for T ˆ 350 K, 335 K, 315 K, and 300 K. (Suggestion: Use a spreadsheet.) 

(c) The equilibrium constant should vary with temperature according to the relation 

Use the results of Part (b) to determine the values of a and b by curve-fitting.

Transcribed Image Text:

T(K) 473 350 335 315 300 Pgauge (atm) 1.00 0.272 0.111 -0.097 -0.224 Pure NO2