Calculating Q to predict direction
For A + B ⇌ C, Kc = 0.5. A mixture has [A] = 1 M, [B] = 2 M, and [C] = 2 M. What happens?
Answer C: explanation for every choice
A
A forward shift happens when Q is less than K.
B
Equilibrium requires Q = K.
C
Correct. Q = [C]/([A][B]) = 2/(1 × 2) = 1. Q is greater than K, so the reaction shifts toward reactants.
D
K is given at this temperature, so the direction can be determined.
TakeawayCalculate Q the same way as K, then compare.
Equation usedEquilibrium constant and reaction quotient
Next question →Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp141.