Nitrogen dioxide and dinitrogen tetroxide interconvert according to N _2 O _4(g) 2 ,…

CHEMISTRY · Multi-part · A Level · Chemistry · Gaseous equilibria (Kp) · Gaseous equilibria (Kp)

Problem

Nitrogen dioxide and dinitrogen tetroxide interconvert according to

\text{N}_2\text{O}_4(g)\rightleftharpoons2\,\text{NO}_2(g)

For the decomposition of one mole of

\text{N}_2\text{O}_4

the enthalpy change is

\Delta H^{\circ}= +58\,\text{kJ}

. At

298\,\text{K}

the equilibrium constant is

K_p = 0.15

. A rigid

10.0\,\text{L}

vessel at

298\,\text{K}

initially contains

0.500\,\text{mol}

\text{N}_2\text{O}_4

and

0.500\,\text{mol}

\text{NO}_2

. After equilibrium is established at

298\,\text{K}

, the vessel is rapidly compressed to

5.00\,\text{L}

and simultaneously heated to

350\,\text{K}

. The temperature and volume changes occur so quickly that no reaction takes place during the transition. (a) Determine the partial pressures of

\text{N}_2\text{O}_4

and

\text{NO}_2

in the vessel at

298\,\text{K}

just before the temperature–volume change occurs. (b) Calculate the value of

K_p

for the reaction at

350\,\text{K}

. (c) Immediately after the simultaneous compression and heating (before any further reaction), calculate the reaction quotient

Q_p

for the mixture now at

350\,\text{K}

and

5.00\,\text{L}

. (d) Predict the direction in which the net reaction will proceed to reach the new equilibrium and justify your prediction. (e) Determine the final equilibrium partial pressures of

\text{N}_2\text{O}_4

and

\text{NO}_2

and the total pressure in the vessel at

350\,\text{K}

. Provide a clear statement of the variables and equations used in your solution.

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