H2(g) + I2(g) 2 HI(g) Kc = 55.3

Step 2

Put equilibrium [ ]

into Kc .

Step 1 Define equilibrium condition in terms of initial condition and a change variable

[H2] [I2] [HI]

At equilibrium 1.00-x 1.00-x 2x

Step 3. Solve for x. 55.3 = (2x)2/(1-x)2

Square root of both sides & solve gives: x = 0.79

[H2] = [I2] = 1.00 - x = 0.21 M

[HI] = 2x = 1.58 M

At equilibrium

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