Hydrogen iodide decomposes at high temperature according to the equation
2 HI(g) ⇌ H2(g) + I2(g)
A 1.50 L reaction vessel at 550 K is initially filled with 0.800 mol HI and 0.200 mol I2. (No H2 is present initially.) The equilibrium constant expressed in terms of pressure for this temperature is Kp = 1.7. Assume ideal-gas behavior.
(a) Calculate the initial partial pressures of HI and I2 in the vessel.
(b) Determine the initial value of Qp for the system.
(c) Predict the direction in which the reaction will proceed to reach equilibrium and justify your answer.
(d) After the system is allowed to equilibrate, an additional 0.100 mol HI (at 550 K) is injected into the vessel without changing the volume or temperature. Immediately after the addition, calculate the new value of Qp and state the direction of the subsequent shift required to reach the new equilibrium.