Nitrogen monoxide dimerizes in the gas phase according to the overall equilibrium (to…

CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

Nitrogen monoxide dimerizes in the gas phase according to the overall equilibrium 2 NO(g)  ⇌  N2O2(g)2\,\mathrm{NO(g)}\;\rightleftharpoons\;\mathrm{N_2O_2(g)} KoverallK_{\text{overall}} (to be determined) A proposed mechanism involves two fast, reversible elementary steps: Step I: NO(g)  ⇌  12 N2(g)+12 O2(g)\mathrm{NO(g)}\;\rightleftharpoons\;\dfrac12\,\mathrm{N_2(g)}+\dfrac12\,\mathrm{O_2(g)} K1K_1 Step II: N2(g)+O2(g)  ⇌  N2O2(g)\mathrm{N_2(g)}+\mathrm{O_2(g)}\;\rightleftharpoons\;\mathrm{N_2O_2(g)} K2K_2 (The fractional coefficients reflect elementary molecular processes.) (a) Confirm, by appropriately combining Steps I and II, that the mechanism is consistent with the given overall reaction. Clearly show the algebraic manipulation of the elementary equations. (b) Express KoverallK_{\text{overall}} in terms of K1K_1 and K2K_2. (c) Suppose Step I is experimentally observed to have K1≪1K_1\ll1 while Step II has K2≫1K_2\gg1. Without computing any numbers, predict whether KoverallK_{\text{overall}} is greater than 1, less than 1, or approximately equal to 1, and justify your reasoning. (d) If the stoichiometric coefficients in Step II were doubled, explain qualitatively how KoverallK_{\text{overall}} would be affected, if at all. Address both the mathematical consequence of the coefficient change and the underlying thermodynamic rationale.

Related theory

Browse the problem library