Chapter 13

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 ${25}^{\circ }\mathrm{C}$ .