Question 19.7: Writing the Expression for a Thermodynamic Equilibrium Const...
Writing the Expression for a Thermodynamic Equilibrium Constant
Write expressions for the thermodynamic equilibrium constants for each of the following reactions:
a. The reaction given in the chapter opening,
2 \mathrm{NH}_{3}(g)+\mathrm{CO}_{2}(g) \rightleftharpoons \mathrm{NH}_{2} \mathrm{CONH}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)
b. The solubility process,
\mathrm{AgCl}(s) \rightleftharpoons \mathrm{Ag}^{+}(a q)+\mathrm{Cl}^{-}(a q)
a. Note that \mathrm{H}_{2} \mathrm{O} is a solvent, so it does not appear explicitly in K. The gases appear in K as partial pressures, and the solute appears as a molar concentration.
K=\frac{\left[\mathrm{NH}_{2} \mathbf{C O N H}_{2}\right]}{\mathbf{P}_{\mathrm{NH}_{3}}^{2} \mathbf{P}_{\mathrm{CO}_{2}}}
b. Note that \mathrm{AgCl} is a solid, so it does not appear explicitly in K. The solutes appear as molar concentrations.
K=\left[\mathrm{Ag}^{+}\right]\left[\mathrm{Cl}^{-}\right]
This is identical to K_{s p}.