A 2.0 L sealed flask at 500 K contains the gaseous species involved in the reaction 2…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A 2.0 L sealed flask at 500 K contains the gaseous species involved in the reaction
2 HI(g) ⇌ H2(g) + I2(g)
The particulate depiction of the flask includes the following counts at one instant:
• 18 individual HI molecules
• 2 individual H2 molecules
• 2 individual I2 molecules
Assume ideal‐gas behavior and that the volume of the container remains constant. The equilibrium constant at 500 K is Kc = 0.015.
(a) Calculate the numerical value of the reaction quotient Qc at the instant shown. Show all steps in your reasoning, including how the particle counts were converted into concentration terms.
(b) Compare Qc to Kc and determine the direction in which the reaction mixture will proceed to reach equilibrium.
(c) Once equilibrium is re-established at 500 K, predict whether the total number of gas molecules in the flask will be greater than, less than, or equal to the current total (22 molecules). Justify your answer in terms of shifts in particle counts dictated by your comparison in part (b).