On heating, gas $X$ undergoes dissociation to establish the equilibrium shown below. $X(g) \rightleftharpoons Y(g) + Z(g)$ A sample of gas $X$ is heated at constant pressure, $p$, at a particular temperature. It is then found that the equilibrium partial pressure of gas $X$ is $\tfrac{1}{7}p$. What is the equilibrium constant, $K_p$, at this temperature?
- A$\tfrac{6}{7}p$
- B$\tfrac{9}{7}p$
- C$\tfrac{36}{7}p$
- D$9p$