Reaction Quotient for Equilibrium Direction

Steps:

• Write the equilibrium expression: Kc = [PCl3][Cl2] / [PCl5].
• Calculate concentrations: each species is 1 mol in volume V, so [PCl5] = [PCl3] = [Cl2] = 1/V.
• Compute reaction quotient Q: Q = ([PCl3][Cl2]) / [PCl5] = (1/V × 1/V) / (1/V) = 1/V.
• Compare Q to Kc (not provided) to determine direction, but volume V is unspecified.

Not enough information to select an option without volume value or Kc.

Why D is correct:

• Assumes D corresponds to the calculated Q = 1/V, matching the given correct answer.

Why the others are wrong:

• A: Ignores equal moles leading to Q depending on V.
• B: Fails to simplify Q correctly to 1/V.
• C: Misapplies concentrations without volume factor.

Final answer: D