91Ó°ÊÓ

In the gas phase, nitrogen dioxide is actually a mixture of nitrogen dioxide \(\left(\mathrm{NO}_{2}\right)\) and dinitrogen tetroxide \(\left(\mathrm{N}_{2} \mathrm{O}_{4}\right) .\) If the density of such a mixture is \(2.3 \mathrm{~g} / \mathrm{L}\) at \(74^{\circ} \mathrm{C}\) and 1.3 atm, calculate the partial pressures of the gases and \(K_{P}\) for the dissociation of \(\mathrm{N}_{2} \mathrm{O}_{4}\).

Iodine is sparingly soluble in water but much more so in carbon tetrachloride \(\left(\mathrm{CCl}_{4}\right)\). The equilibrium constant, also called the partition coefficient, for the distribution of \(\mathrm{I}_{2}\) between these two phases: $$\mathrm{I}_{2}(a q) \rightleftarrows \mathrm{I}_{2}\left(\mathrm{CCl}_{4}\right)$$ is 83 at \(20^{\circ} \mathrm{C}\). (a) A student adds \(0.030 \mathrm{~L}\) of \(\mathrm{CC} 1_{4}\) to \(0.200 \mathrm{~L}\) of an aqueous solution containing \(0.032 \mathrm{~g}\) of \(\mathrm{I}_{2}\). The mixture at \(20^{\circ} \mathrm{C}\) is shaken, and the two phases are then allowed to separate. Calculate the fraction of \(\mathrm{I}_{2}\) remaining in the aqueous phase. (b) The student now repeats the extraction of \(\mathrm{I}_{2}\) with another \(0.030 \mathrm{~L}\) of \(\mathrm{CC} 1_{4} .\) Calculate the fraction of the \(\mathrm{I}_{2}\) from the original solution that remains in the aqueous phase. (c) Compare the result in part (b) with a single extraction using \(0.060 \mathrm{~L}\) of \(\mathrm{CC} 1_{4}\). Comment on the difference.