A 1.00 L sealed flask at 25 °C contains gaseous dinitrogen tetroxide and nitrogen…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A 1.00 L sealed flask at 25 °C contains gaseous dinitrogen tetroxide and nitrogen dioxide at equilibrium according to the balanced equation
N2O4(g)⇌2NO2(g)
At this temperature the equilibrium constant is Kc=4.6×10−3.
Before any disturbance the measured concentrations are
[ N2O4]=0.040M and [NO2]=0.0136M.
The flask is then disturbed by injecting enough NO2 gas to raise its concentration instantaneously by 0.0100M, while the volume and temperature remain constant.
(1) Calculate the numerical value of the reaction quotient Qc immediately after the injection.
(2) Compare the value of Qc to Kc and indicate the direction in which the reaction will proceed as the system approaches a new equilibrium. Explain your reasoning.
(3) Qualitatively describe how the concentrations of N2O4 and NO2 will change (increase, decrease, or remain approximately constant) as the new equilibrium is attained.
(4) Nitrogen dioxide is brown while dinitrogen tetroxide is colorless. Predict whether the brown color in the flask will become darker, lighter, or remain unchanged after equilibrium is re-established, and justify your prediction based on your answers above.