# Problem: An equilibrium mixture of H2, I2, and HI at 458 oC contains 0.112 mol H2, 0.112 mol I2, and 0.775 mol HI in a 5.00-L vessel.What are the equilibrium partial pressure of HI when equilibrium is reestablished following the addition of 0.200 mol of HI?

###### FREE Expert Solution

We are being asked to determine the equilibrium partial pressure of HI.

Reaction: 2 HI(g) ⇌ H2(g) + I2(g)

When dealing with equilibrium:

Kc → equilibrium units are in molarity
Kp → equilibrium units in terms of pressure

To calculate for the equilibrium partial pressure, we will use KC.

Kc , like other equilibrium constants, is the ratio of products to reactants.

We derive Kc for the reaction

${\mathbf{K}}_{\mathbf{C}}\mathbf{=}\frac{\left[{\mathbf{H}}_{\mathbf{2}}\right]\left[{\mathbf{I}}_{\mathbf{2}}\right]}{{\left[\mathbf{HI}\right]}^{\mathbf{2}}}$

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###### Problem Details

An equilibrium mixture of H2, I2, and HI at 458 oC contains 0.112 mol H2, 0.112 mol I2, and 0.775 mol HI in a 5.00-L vessel.

What are the equilibrium partial pressure of HI when equilibrium is reestablished following the addition of 0.200 mol of HI?