Answer
K = $6.9\times10^{-4}$
Work Step by Step
According to the law of mass action, a general formula of the form
jA + kB ⇌ lC + mD
is represented by the following equilibrium expression:
K = $\frac{[C]^{l}[D]^{m}}{[A]^{j}[B]^{k}}$
where A, B, C, and D represent the chemical species and j, k, l, and m are their coefficients in the balanced equation.
Therefore,
K = $\frac{[NO]^{2}}{[N_{2}][O_{2}]}$
K = $\frac{(4.7\times10^{-4})^{2}}{(4.1\times10^{-2})(7.8\times10^{-3})}$
K = $6.91\times10^{-4}$ (carried one extra significant digit)
K = $6.9\times10^{-4}$
