chemistry question

Question

At 60°C, the reaction, PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) has a K value of12.5. If the reaction quotient, Q, calculated from initial concentrations is 19.8 at 60°C, which of the following statements is correct?

1. the rate of the reverse reaction is equal to the rate of forward reaction
2. there is more reactant concentration than product concentration
3. the system is already at equilibrium
4. system must shift to the right to reach equilibrium
5. system must shift to the left to reach equilibrium

Answer 1

PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) ... K = 12.5

If Q = 19.8, which is greater than the K of 12.5, this indicates that compared to the equilibrium situation, there is now MORE product and LESS reactant than at equilibrium. Thus, in order to attain equilibrium the reaction would have to shift to the left to get rid of some product and make more reactants.

So, the answer would be #5. system must shift to the left to reach equilibrium