Consider the reaction:

2Mg + O2 ------> 2MgO

The reaction is at equilibrium, the concentration of MgO is found to be 0.5.

What is the concentration of Mg and O2?
-------------------------------------------------------

Keq is not given... using the ICE table, I ended up with the following:

Keq = [MgO]^2 / [Mg]^2 * [O2]

Keq = [0.5]^2 / [2x - 0.5]^2 * [x - 0.5]

Keq = 0.25 / 2x(x - 1) + 0.25

Not sure what to do.. or if I'm even going in the right direction

To solve this problem, you are on the right track with using the ICE table and the equilibrium constant expression (Keq). However, it seems that you made a mistake in writing the expression for Keq.

For the balanced equation 2Mg + O2 → 2MgO, the Keq expression should be:

Keq = [MgO]^2 / ([Mg]^2 * [O2])

Let's proceed with solving for the concentrations of Mg and O2.

Given: [MgO] = 0.5

Assuming that the initial concentrations of Mg and O2 are x, we can set up the ICE table:

2Mg + O2 ⇌ 2MgO
I: x x 0
C: -2x -x +2x
E: x - 2x x - x + 2x

From the E row of the table, we can see that the equilibrium concentrations of Mg and O2 are 0, while the equilibrium concentration of MgO is 2x.

Now, substitute these values into the Keq expression:

Keq = (2x)^2 / (x^2 * (0))

Since the concentration of O2 is 0 at equilibrium, the denominator of the Keq expression becomes zero.

However, mathematically, we cannot divide by zero. Therefore, we cannot determine the concentrations of Mg and O2 using this method.

To find the concentrations of Mg and O2, we would need additional information, such as the value of Keq or the initial concentrations of Mg and O2.