At 800 K the water–gas shift reaction reaches equilibrium according to CO (g)+ H _2 O…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
At 800 K the water–gas shift reaction reaches equilibrium according to
CO(g)+H2O(g)⇌CO2(g)+H2(g),Kc=0.64
Four sealed 2.00 L reaction vessels are prepared at 800 K with the initial molar amounts shown in the table.
Vessel
CO (mol)
H2O (mol)
CO2 (mol)
H2 (mol)
A
0.80
0.80
0.10
0.10
B
0.40
0.40
0.40
0.40
C
0.10
0.80
0.80
0.10
D
0.10
0.10
0.80
0.80
Assume ideal–gas behavior throughout.
(a) Calculate the initial concentration of each species (in mol L−1) for all four vessels.
(b) Determine the numerical value of the reaction quotient Qc for each vessel immediately after preparation.
(c) Using the values obtained in part (b), rank the vessels from the one requiring the largest net forward reaction progress to the one requiring the largest net reverse reaction progress before equilibrium is re-established. Clearly indicate any vessels that require negligible shift.
(d) Justify your ranking quantitatively by comparing the magnitude and sign of the quantity KcQc−Kc for each vessel.