Phosgene forms from carbon monoxide and chlorine gas according to the reversible…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Phosgene forms from carbon monoxide and chlorine gas according to the reversible reaction
CO(g)+Cl2(g)⇌COCl2(g)
At a particular temperature the equilibrium constant Kc=9.0. A rigid container of fixed volume contains a total of 60 gas particles distributed among the three species. Four different particulate diagrams (P1–P4) are proposed as possible snapshots of the system at equilibrium; the particle counts for each diagram are listed:
• P1: 12 CO, 12 Cl_2, 36 COCl_2
• P2: 18 CO, 18 Cl_2, 24 COCl_2
• P3: 24 CO, 24 Cl_2, 12 COCl_2
• P4: 10 CO, 20 Cl_2, 30 COCl_2
Assume concentrations are proportional to particle counts.
(a) Let the equilibrium concentrations of CO, Cl2, and COCl2 be represented by c, c, and x respectively. Write the algebraic expression for Kc in terms of c and x.
(b) Using the constraint of 60 total particles, derive the theoretical equilibrium particle counts that exactly satisfy Kc=9.0. Round each count to the nearest whole particle.
(c) Compare your theoretical counts with each diagram’s counts. Identify the diagram that best matches the equilibrium condition and calculate the percent deviation for each species in that diagram relative to your theoretical values.
(d) Provide two possible experimental or representational reasons that could account for the small discrepancies between the theoretical counts and the counts in the diagram you selected.