The Reaction Quotient Video Lessons

Example

# Problem: A system at equilibrium contains I2(g) at a pressure of 0.27 atm and I(g) at a pressure of 0.26 atm . The system is then compressed to half its volume.Find the pressure of I2 when the system returns to equilibrium.

###### FREE Expert Solution

We are being asked to find the pressure of I2 when the system returns to equilibrium. The given reaction is:

I2(g)  2 I(g)

We're going to calculate the pressure of I2 using the following steps:

Step 1: Calculate the equilibrium constant, Kp.
Step 2: Calculate the pressure after the system was compressed to half its volume.
Step 3: Calculate Q and determine the direction of reaction to reestablish the equilibrium.
Step 4: Set up an ICE chart and calculate the equilibrium pressure of I2.

Step 1: Calculate the equilibrium constant, Kp.

Given at equilibrium:

P I2(g) = 0.27 atm
P I(g) = 0.26 atm

$\overline{){{\mathbf{K}}}_{{\mathbf{p}}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}}\phantom{\rule{0ex}{0ex}}{\mathbf{K}}_{\mathbf{p}}\mathbf{=}\frac{{\mathbf{\left(}{\mathbf{P}}_{\mathbf{I}}\mathbf{\right)}}^{\mathbf{2}}}{{\mathbf{P}}_{{\mathbf{I}}_{\mathbf{2}}}}\phantom{\rule{0ex}{0ex}}{\mathbf{K}}_{\mathbf{p}}\mathbf{=}\frac{{\mathbf{\left(}\mathbf{0}\mathbf{.}\mathbf{26}\mathbf{\right)}}^{\mathbf{2}}}{\mathbf{0}\mathbf{.}\mathbf{27}}$

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###### Problem Details

A system at equilibrium contains I2(g) at a pressure of 0.27 atm and I(g) at a pressure of 0.26 atm . The system is then compressed to half its volume.

Find the pressure of I2 when the system returns to equilibrium.