The following reactions occur at 500 K. Arrange them in order of increasing tendency to proceed to completion (least completion → greatest completion).

Question

Quizplus · Accepted Answer

The reaction quotient, Qc, helps to predict the direction in which a reaction will proceed towards equilibrium. For each reaction, we can calculate its Qc using the given initial concentrations and the stoichiometric coefficients of the reactants and products.

Qc for reaction 1:
Qc = [NH3]^2/[N2][H2]^3 = (0.1 M)^2/[(0.2 M)(0.3 M)^3] = 6.17 x 10^-3

Qc for reaction 2:
Qc = [H2S][NH3]^3/[NH4+][HS^-]^2 = (0.1 M)(0.1 M)^3/[(0.05 M)(0.05 M)^2] = 1.6 M

Qc for reaction 3:
Qc = [H2O][CO]/[H2][CO2] = (0.2 M)(0.2 M)/[(0.3 M)(0.1 M)] = 1.33

Qc for reaction 4:
Qc = [NOCl]^2/[NO]^2[Cl2] = (0.05 M)^2/[(0.1 M)^2(0.1 M)] = 0.5

Comparing the calculated Qc values for each reaction, we can see that reaction 4 has the smallest Qc, indicating that this reaction is the most likely to proceed to completion. Reaction 3 has the next smallest Qc, followed by reaction 1 and then reaction 2, which has the largest Qc. Therefore, the correct answer is choice C, 3 < 4 < 1 < 2, indicating that reaction 3 has the least tendency to proceed to completion, followed by reaction 4, reaction 1, and finally reaction 2, which has the greatest tendency to proceed to completion.

The Following Reactions Occur at 500 K