A gaseous material \(\mathrm{XY}(g)\) dissociates to some extent to produce
\(\mathrm{X}(g)\) and \(\mathrm{Y}(g) :\)
$$\mathrm{XY}(g) \rightleftharpoons \mathrm{X}(g)+\mathrm{Y}(g)$$
A 2.00 -g sample of \(\mathrm{XY}\) (molar mass \(=165 \mathrm{g} / \mathrm{mol}
)\) is placed in
a container with a movable piston at \(25^{\circ} \mathrm{C}\) . The pressure is
held constant at 0.967 \(\mathrm{atm} .\) As \(\mathrm{XY}\) begins to dissociate,
the piston moves until 35.0 mole percent of the original \(\mathrm{XY}\) has
dissociated and then remains at a constant position. Assuming ideal behavior,
calculate the density of the gas in the container after the piston has stopped
moving, and determine the value of \(K\) for this reaction of \(25^{\circ}
\mathrm{C}\) .
