Hydrogen iodide breaks down into hydrogen and iodine. $2\text{HI}(g) \rightleftharpoons \text{H}_2(g) + \text{I}_2(g)$ In an experiment, $b$ mol of hydrogen iodide was placed in a sealed vessel under pressure $p$. When equilibrium was reached, $x$ mol of the hydrogen iodide had dissociated. Which expression for $K_p$ is correct?
- A$\frac{x^2}{(b-x)^2}$
- B$\frac{x^2p^2}{(b-x)^2}$
- C$\frac{x^2p^2}{4b(b-x)}$
- D$\frac{x^2}{4(b-x)^2}$