At 400 K, the equilibrium constant for the reaction Br2 (g) + Cl2 (g) ↔ 2BrCl (g) is Kp = 7.0. A closed vessel at 400 K is charged with 1.00 atm of Br2 (g), 1.00 atm of Cl2 (g), and 2.00 atm of BrCl (g). Use Q to determine which of the statements below is true.

(a) - The equilibrium partial pressure of BrCl (g) will be greater than 2.00 atm.

(b) - The equilibrium partial pressure of Br2 will be greater than 1.00 atm.

(c) - At equilibrium, the total pressure in the vessel will be less than the initial total pressure.

(d) - The reaction will go to completion since there are equal amounts of Br2 and Cl2.

(e) - The equilibrium partial pressures of Br2, Cl2, and BrCl will be the same as the initial values.

(a) The equilibrium partial pressure of BrCl (g) will be greater than 2.00 atm.

Explanation:

Q is the coefficient of the reaction and is calculated the same of the way of the equilibrium constant, but using the concentrations or partial pressures in any moment of the reaction, so, for the reaction given:

Q = (pBrCl) ² / (pBr₂*pCl₂)

Q = 2² / (1x1)

Q = 4

As Q < Kp, the reaction didn't reach the equilibrium, and the value must increase. As we can notice by the equation, Q is directly proportional to the partial pressure of BrCl, so it must increase, and be greater than 2.00 atm in the equilibrium.

The partial pressures of Br₂ and Cl₂ must decrease, so they will be smaller than 1.00 atm. And the total pressure must not change because of the stoichiometry of the reaction: there are 2 moles of the gas reactants for 2 moles of the gas products.

Because is a reversible reaction, it will not go to completion, it will reach an equilibrium, and as discussed above, the partial pressures will change.