Chapter 12, Problem 119MP

A gaseous material XY(g) dissociates to some extent to produce X(g) and Y(g):

$\text{XY}\left(g\right)\rightleftharpoons \text{X}\left(g\right)+\text{Y}\left(g\right)$

A 2.00-g sample of XY (molar mass = 165 g/mol) is placed in a container with a movable piston at 25°C. The pressure is held constant at 0.967 atm. As XY begins to dissociate, the piston moves until 35.0 mole percent of the original 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°C.