A 20.0 mL syringe sealed with a frictionless plunger contains 3.0 mL of liquid water…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A 20.0 mL syringe sealed with a frictionless plunger contains 3.0 mL of liquid water and water vapor at 25 °C.
The plunger is suddenly pulled outward to double the gas volume inside the syringe. The temperature remains constant throughout the experiment.
Answer the following questions about the behavior of the system.
(a) Describe qualitatively how the rates of evaporation and condensation change immediately after the plunger is pulled outward and as time progresses toward a new steady state.
(b) Once the syringe has been left undisturbed for a long time, the internal pressure becomes constant. Explain why the macroscopic pressure stops changing even though molecular motion continues.
(c) The plunger is now pushed back to its original position in a single quick motion, returning the gas volume to its initial value. Discuss whether the sequence of pulling the plunger out and then pushing it back in constitutes a reversible or an irreversible overall process under the experimental conditions. Justify your answer based on the definition of reversibility.
(d) Propose two specific modifications to the experimental setup that would allow the same volume change to occur in a way that more closely approaches a truly reversible path. Explain how each modification addresses the criteria for reversibility.