A rigid, sealed flask contains liquid in equilibrium with at . After several minutes…
CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A rigid, sealed flask contains liquid Br2(ℓ) in equilibrium with Br2(g) at 25∘C. After several minutes the reddish-brown color intensity of the vapor space stops changing, but infrared spectroscopy shows that gaseous Br2 molecules continue to collide with and leave the liquid surface.
Which of the following statements is most consistent with these observations?
(a) Static equilibrium has been reached; no molecules cross the liquid–vapor interface.
(b) Dynamic equilibrium has been established; molecules continue to exchange while the rates of vaporization and condensation are equal.
(c) The vaporization process has ceased; the unchanging colour shows that the reverse (condensation) process is now favoured.
(d) Condensation now occurs more rapidly than vaporization, but the excess energy is absorbed by the liquid so the vapour colour remains constant.