Chapter 10

For the chemical reactions shown below, write an expression for the equilibrium constant in terms of the partial pressures of the reactants and products. 1\. \(\mathrm{PCl}_{5}(g) \rightleftarrows \mathrm{PCl}_{3}(g)+\mathrm{Cl}_{2}(g)\) 2\. \(2 \mathrm{NOCl}(g) \rightleftarrows 2 \mathrm{NO}(g)+\mathrm{Cl}_{2}(g)\) 3\. \(\mathrm{PCl}_{3}(g)+3 \mathrm{NH}_{3}(g) \rightleftarrows \mathrm{P}\left(\mathrm{NH}_{2}\right) 3(g)+3 \mathrm{HCl}(g)\)

1\. Nitrous acid (HNO2) is a weak acid with a \(K_{\mathrm{a}}\) of \(4.3 \times 10^{-4}\). Estimate the hydronium ion concentration and the \(p \mathrm{H}\) for a \(0.50 \mathrm{M}\) solution of nitrous acid in distilled water. 2\. Acetic acid is a weak acid with \(K_{a}=1.8 \times 10^{-5}\). For a solution of acetic acid in water, the \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]\) is found to be \(4.2 \times\) \(10^{-3} \mathrm{M}\). What is the concentration of unionized acetic acid in this solution? $$ \mathrm{CH}_{3} \mathrm{COOH}(a q)+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightleftarrows \mathrm{CH}_{3} \mathrm{COO}^{-}(a q)+\mathrm{H}_{3} \mathrm{O}^{+}(a q) $$ 3\. A solution is prepared in which acetic acid is \(0.700 \mathrm{M}\) and its conjugate base, acetate anion is \(0.600 \mathrm{M}\). As shown above, the \(K_{\mathrm{a}}\) of acetic acid is \(1.8 \times 10^{-5}\); what will the \(p \mathrm{H}\) of this solution be?

For the reaction between carbon monoxide and chlorine to form phosgene, the equilibrium constant calculated from partial pressures is \(K=0.20 .\) How does this value relate to the equilibrium constant, \(K_{\mathrm{C}}\), under the same conditions, calculated from molar concentrations? $$ \mathrm{CO}(g)+\mathrm{Cl} 2(g) \rightleftarrows \mathrm{COCl} 2(g) $$