A reaction vessel is charged with hydrogen iodide, which partially decomposes to molecular hydrogen and iodine: 2HI (g) H₂(g) + I₂(g)
When the system comes to equilibrium at 425 °C, P_HI = 0.708 atm, and P_H₂ = P_I₂ = 0.0960 atm. The value of K_p at this temperature is ________.

Question

A reaction vessel is charged with hydrogen iodide, which partially decomposes to molecular hydrogen and iodine: 2HI (g)

H₂(g) + I₂(g)
When the system comes to equilibrium at 425 °C, P_HI = 0.708 atm, and P_H₂ = P_I₂ = 0.0960 atm. The value of K_p at this temperature is ________.

Quizplus · Accepted Answer

The equilibrium constant (Kp) can be calculated using the following equation:

Kp = (P(I2) x P(H2)) / P(HI)^2

Substituting the given values:

Kp = (0.0960)^2 / 0.708 = 0.01305 atm^2

Using the ideal gas law, we can convert atm^2 to (atm)^-1 (mol/L)^2, which is the unit of Kp:

Kp = (0.01305 atm^2) / (0.0821 L.atm/K.mol x 698 K)^2 = 1.84 x 10^-2 (atm)^-1 (mol/L)^2

Therefore, the value of Kp is 1.84 x 10^-2 (atm)^-1 (mol/L)^2, which can also be written as 1.84 x 10^-12 in scientific notation. The closest answer choice is D, which is 1.84 x 10^-12 written in scientific notation.

A Reaction Vessel Is Charged with Hydrogen Iodide, Which Partially