Dinitrogen tetroxide decomposes according to the equilibrium reaction N_2O_4(g) ; ;2…

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

Problem

Dinitrogen tetroxide decomposes according to the equilibrium reaction

\mathrm{N_2O_4(g)}\;\longleftrightarrow\;2\,\mathrm{NO_2(g)}

with

\Delta H_{rxn}>0

. A sealed 10.0 L steel cylinder at 298 K initially contains an equilibrium mixture in which the partial pressure of

\mathrm{N_2O_4}

is 0.80 atm and that of

\mathrm{NO_2}

is 0.40 atm. Answer the following questions about possible industrial manipulations designed to increase the molar fraction of

\mathrm{NO_2}

in the product stream. (a) The total pressure inside the cylinder is suddenly doubled by decreasing the volume at constant temperature. Describe qualitatively how the amounts of

\mathrm{N_2O_4}

and

\mathrm{NO_2}

will change as the system moves toward its new equilibrium. Justify your answer. (b) Instead of changing the volume, the temperature of the cylinder is raised from 298 K to 333 K at constant volume. Predict the direction in which the equilibrium will shift and explain your reasoning. (c) Identify two different concentration (or partial-pressure) adjustments—other than changing total pressure—that plant engineers could make to increase the production of

\mathrm{NO_2}

. For each adjustment, justify how it would alter the position of equilibrium.

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