?

AP® Chemistry

Free Version

Upgrade subject to access all content

Difficult

Evaluating $K$ for Gaseous Equilibria

APCHEM-CEBN5J

$$P{ Cl }_{ 5 }(g) \rightleftarrows P{ Cl }_{ 3 }(g) + { Cl }_{ 2 }(g)$$

Gaseous phosphorus pentachloride decomposes into phosphorus trichloride and chlorine gas, as shown by the equation above.

A pure sample of $P{ Cl }_{ 5 }(g)$ is placed into a rigid, evacuated container at a particular temperature; the initial partial pressure of $P{ Cl }_{ 5 }(g)$ is 1.00 atm, as shown in the first figure. The decomposition is allowed to occur at a constant temperature.

When reaction ceases, the system has the composition shown in the second figure, with a total pressure of 1.50 atm.

Created for Albert.io. Copyright 2016. All rights reserved.

Created for Albert.io. Copyright 2016. All rights reserved.

Based on the information in the figures and in the preceding description, which of the following can be concluded concerning this system?

A

The value of the equilibrium constant, ${ K }_{ p }$, is 1.00.

B

The value of the equilibrium constant, ${ K }_{ p }$, is greater than 1.00.

C

The equilibrium partial pressures of all three gases are 0.50 atm.

D

Since reaction has ceased, we can conclude that all of the $P{ Cl }_{ 5 }(g)$ has been consumed.