What is the relative concentration of reactants and products at equilibrium?

If we consider the equilibrium constant expression you can easily predict the answer. Suppose the equilibrium reaction is as follows: A(g) + B(g) <> C(g) + D(g) K = [C][D] / [A][B] Now, if K >>>1 this means that numerator is much more greater than denominator. That is, you have more C and D than A and B. Most of the reactants are converted to the products. The forward reaction is more effective. If K <<<1 this means that denominator is much more greater than numerator. That is, you have more A and B than C and D. A small portion of the reactants are converted to the products. The reverse reaction is more effective.

The air is going to come out because of the low pressure.