Chapter 12, Problem 103CP

At 25°C. K_p = 5.3 × 10⁵ for the reaction

${\text{N}}_2\left(g\right)+3{\text{H}}_2\left(g\right)\rightleftharpoons 2{\text{NH}}_3\left(g\right)$

When a certain partial pressure of NH₃(g) is put into an otherwise empty rigid vessel at 25°C, equilibrium is reached when 50.0% of the original ammonia has decomposed. What was the original partial pressure of ammonia before any decomposition occurred?