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Chemistry question regarding equilibrium and ICE table?

A mixture of 0.1532 M Cl2 (g) and 0.1532 M I2(g) was allowed to react and come to equilibrium at some temperature. If Kc = 1.492e5, what is the equilibrium molar concentration of ICl for the reaction?

Cl2(g) + I2(g) <-> 2ICl(g)

I made an ICE table and when I plugged all the values into the Kc equation and then did the quadratic formula, I got a negative number underneath the square root. I'm not sure what I'm doing wrong, please help!

1 Answer

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  • 9 years ago
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    Hello,

    R: Cl2(g) + I2(g) <-> 2ICl(g)

    I: .1532M .1532M 0

    C: -x -x +2x

    eq: .1532-x .1532-x 2x

    Kc = 1.492E5 = [ICI]^(2) / [Cl2][I2]

    1.492E5 = [2x]^(2) / [.1532-x][.1532-x]

    **The trick here is, since the denominator of [.1532-x][.1532-x] is the same as [.1532-x]^(2) & the numerator is squared as well, we can square root both sides (thus the "quadratic equation" is not necessary).

    1.492E5 = [2x]^(2) / [.1532-x]^(2)

    sqrt (1.492E5) = sqrt ([2x]^(2)) / sqrt([.1532-x]^(2))

    386.3 = [2x] / [.1532-x]

    59.2 - 386.3x = 2x

    59.2 = 388.3x

    .152 M = x

    Since the concentration of ICl(g) at equilibrium is equal to 2x....

    [ICl]equilibrium = 2x = 2 (.152M) = .304M

    Source(s): U of H Brain
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