The formation of hydrogen iodide is described by H_2(g) + I_2(g) ; ;2 ,HI(g) At 458 K…

CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

The formation of hydrogen iodide is described by

\mathrm{H_2(g) + I_2(g)\;\rightleftharpoons\;2\,HI(g)}

At 458 K a mixture in a 2.00 L rigid vessel is at equilibrium with the following measured concentrations:

[\mathrm{HI}]=1.80\,\text{M}

[\mathrm{H_2}]=0.200\,\text{M}

[\mathrm{I_2}]=0.200\,\text{M}

The vessel is then rapidly expanded to a new fixed volume of 4.00 L while the temperature is kept at 458 K. No material is added or removed. After sufficient time the system again attains equilibrium. (1) Determine the numerical value of

K_c

for the reaction at 458 K using the initial equilibrium data. (2) Immediately after the volume expansion but before any shift toward a new equilibrium occurs, calculate the molar concentration of each species in the vessel. (3) Identify the direction in which the reaction proceeds to re-establish equilibrium and justify your answer in terms of

Q

and

K_c

. (4) Calculate the equilibrium concentrations of all species in the expanded vessel and state how many moles of

\mathrm{HI}

decompose during the readjustment.

Related theory

Browse the problem library