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Calculating Equilibrium Concentrations

Calculating Equilibrium Concentrations.

Consider the reaction SO2(g) + NO2(g) = NO(g) + SO3(g) at 460 C. What are the equilibrium concentrations of all reactants and products if the initial concentrations are [SO2]o = [NO2]o = 3.00 x 10-3 M and [NO]o = [SO3]o = 4.00 x 10-2 M? The value of the equilibrium constant for the reaction is 85.0 at 460 C.

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Set up table with initial, change, and equilibrium expressions:

SO2(g) + NO2(g) = NO(g) + SO3(g)

I 3x10-3 3x10-3 4x10-2 4x10-2

C -x -x +x +x

E 3x10-3 -x 3x10-3 -x 4x10-2 +x 4x10-2 +x

Keq = [NO][SO3]/[SO2][NO2] = (3x10-3 -x)^2 / (4x10-2 +x)^2 = 85.0

Solve this equation for x... Hint: take the square root of both sides first

Then plug in your value of x into the table above for the equilibrium row (E) and solve for all the equilibrium concentrations.

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