Phosgene reacts with water according to the balanced chemical equation: H _2 O (l)+…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Phosgene reacts with water according to the balanced chemical equation:
H2O(l)+COCl2(g)⇌2HCl(g)+CO2(g)
Depending on experimental conditions, water may behave as a reacting solvent or as a gaseous reactant.
(a) Write the equilibrium-constant expression Kp appropriate for a closed, rigid container that initially contains only gaseous phosgene and a trace amount (<1mol%) of gaseous water at 298 K.
(b) Write the equilibrium-constant expression Kc that would be used if the reaction is conducted in an aqueous solution containing an excess of liquid water that remains in a separate phase throughout the experiment.
(c) Discuss why the treatment of H2O differs between parts (a) and (b), making explicit reference to physical phase and how that influences inclusion or exclusion in equilibrium expressions.