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# Equilibrium or Not?

APCHEM-KMMLIW

The reaction between ozone, ${ O }_{ 3 }(g)$, and nitrogen monoxide (also known as nitric oxide), $NO(g)$, produces nitrogen dioxide, $N{ O }_{ 2 }(g)$, and oxygen gas, ${ O }_{ 2 }(g)$. At a particular temperature, the value of $K$ for the reaction is known to be 16.

$${ O }_{ 3 }(g)+NO(g)\rightleftharpoons { O }_{ 2 }(g)+N{ O }_{ 2 }(g)\qquad K=16$$

In a particular experiment, the following samples of ozone and nitric oxide are allowed to react.

Consider the following mixture of ozone, nitrogen monoxide, nitrogen dioxide, and oxygen gas.

Which of the following explains if this is a possible equilibrium mixture, resulting from the initial concentrations of ${ O }_{ 3 }(g)$ and $NO(g)$?

A

No.

$Q < K$, so the system will shift to the right.

B

No.

$Q = K$, but this is not a possible equilibrium mixture, given the initial system composition and the stoichiometry of the reaction. Atoms are not conserved in this system.

C

No.

$Q > K$, so the system will shift to the left.

D

Yes.

$Q = K$, so the system will maintain the current composition with no further shifts occurring. The forward and reverse reactions will continue but at equal rates.