Why is this incorrect? Consider the reaction #A + B rightleftharpoons C + D#. If #[A] = [B] = "2.00 M"# initially, and #K_c = 6.5#, determine #x#?

Question

I keep getting #x = 1.23# but it's not right...

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Answer 1 · 2015-04-28T14:54:48

You used #sqrt(K_"c")# instead of #K_"c"# in your equilibrium constant expression.

You used #sqrt(K_"c")# instead of #K_"c"# in your equilibrium constant expression.

Let's set up an ICE table.

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#K_"c" = "[C][D]"/"[A][B]" = x^2/(2.00-x)^2 = 6.5#

#x/(2.00-x) = sqrt6.5 = 2.55#

#color(highlight)(x) = 2.55(2.00-x) = color(highlight)(5.10 -2.55x)#

#3.55x = 5.10#

#x = 1.44#