Nitrogen dioxide can dimerize to form dinitrogen tetroxide according to the…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Nitrogen dioxide can dimerize to form dinitrogen tetroxide according to the reversible reaction 2NO2(g)⇌N2O4(g). The dimerization is modeled as the sum of two elementary equilibria: Step 1: NO(g)+21O2(g)⇌NO2(g), Kc1=1.2×105. Step 2: 2NO(g)+O2(g)⇌N2O4(g), Kc2=2.0×106.
(a) Starting from Steps 1 and 2, construct the balanced overall equation that yields 2NO2(g)⇌N2O4(g). Show all intermediate algebraic manipulations required to reach the target stoichiometry.
(b) Determine Kc,overall numerically for the dimerization, giving your answer in scientific notation.
(c) A sealed 5.00 L flask at this temperature is charged with 0.0200 mol of NO2 and no N2O4. Calculate the reaction quotient Qc for dimerization in the flask immediately after charging.
(d) Using your result from part (b), predict the direction in which the system proceeds to reach equilibrium. Quantitatively justify your prediction.
(e) Describe qualitatively how the magnitude of the equilibrium constant obtained in part (b) influences the brown-to-colorless change observed as equilibrium is approached.