What does the equilibrium constant mean for reactions with very small concentrations? When you calculate the equilibrium constant for a reaction with a higher concentration of reactants, the answer is fairly intuitive. For example, for the reaction:
$$\ce{A + B &lt;=&gt; C}$$
Where we have $0.10 M$ of A, $0.30 M$ of B and $0.45$ M of C the equation for the equilibrium constant is:
$$ K = \frac{[0.45]}{[0.10][0.30]} = 15$$
This is relatively intuitive, we can see that the concentration of C is larger than the product of A and B and so saying the products are favoured makes sense.
However, an issue comes about when you consider really small amounts of all of them. For example, for the same reaction
$$\ce{A + B &lt;=&gt; C}$$
If we have $2.4*10^{-4} M$ of A, $2.4*10^{-4} M$ of B and $7.5*10^{-6} M$ of C we have the equation:
$$ K = \frac{[7.5*10^{-6}]}{[2.4*10^{-4}][2.4*10^{-4}]} = 130$$
In this case, the equilibrium constant suggests the products are favoured but if you look at how much product we have compared to reactants there's so much more reactants than products. The constant makes sense since multiplying two numbers less than 1 will get a smaller number but it's confusing when you consider the implications that has on the equilibrium. My immediate assumption is that I am misunderstanding the relationship between the equilibrium constant and the concentrations of species in the reaction and if this is the case is there a more intuitive way of looking at this?
&quot;In this case, the equilibrium constant suggests the products are favoured but if you look at how much product we have compared to reactants there's so much more reactants than products.&quot;  This is what I take as the heart of your question.  To that point:
I believe you need to compare the concentration of all the reactantS, not just one of the products.  In this case, the concentration of all of the reactants is 5.76 X 10 -8 which is a lot less than the 2.4 X 10 -4 which you might have been comparing to the product in the equation.