Chemistry - Chemical Equilibrium Question with Solution | TestHub
A 300 mL flask and a 100 mL flask are separated by a stopcock. At 300 K, nitric oxide in the larger flask exerts a pressure of 0.4 atm, and the smaller one contains oxygen at 1.0 atm. The gases are mixed by opening the stopcock. The reactions occurring are:
2NO + O2 → 2NO2 ⇌ N2O4
The first reaction is complete while the second one is at equilibrium. Assuming all the gases to behave ideally, the Kp for the second reaction if the total pressure is 0.3 atm is
Options:
Answer:
Solution:
At the same temperature moles are proportional to PV (atm mL) NO: 0.4×300 = 120 units and O2: 1.0×100 = 100 units
2NO + O2 → 2NO2 uses 120 units of NO and 60 of O2, giving 120 units of NO2 and leaving 40 units of O2
Let y units of N2O4 form: NO2 = 120 - 2y, N2O4 = y, O2 = 40
Total = 160 - y units, and the total volume is 400 mL at 0.3 atm, so total = 0.3×400 = 120 units
y = 40, so NO2 = 40 and N2O4 = 40 units
PNO2 = (40/120)(0.3) = 0.1 atm and PN2O4 = (40/120)(0.3) = 0.1 atm
Kp = 0.1/(0.1)2 = 10 atm-1
This is option (a).
