A sealed, temperature-controlled flask contains a small amount of liquid bromine and…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A sealed, temperature-controlled flask contains a small amount of liquid bromine and bromine vapor above it. Observations are recorded for several hours and show that, after an initial period, the total mass of liquid bromine remains unchanged even though individual molecules continue to evaporate and condense.
Use this information to analyze the behavior of the system in terms of chemical equilibrium.
(a) Describe what is meant by a dynamic equilibrium in the context of the bromine system.
(b) Identify two specific experimental observations that would indicate the system has reached equilibrium.
(c) Explain, at the particulate level, why the measured mass of liquid bromine remains constant once equilibrium is established even though molecules continue to move between phases.
(d) The temperature of the flask is suddenly increased by 10 K. Predict qualitatively how the rates of evaporation and condensation, the vapor pressure, and the mass of liquid bromine will each change immediately after the temperature jump and after a new equilibrium is attained. Justify each prediction.