GCEChemistryChemical Equilibrium2019

For the reaction $PCl_5(g) \rightleftharpoons PCl_3(g) + Cl_2(g)$, if the value of $K_c$ at a given temperature is very large (e.g. $K_c \gg 1$), this indicates that at equilibrium

AThe reaction has not proceeded significantly
BThe mixture contains mostly reactants
CThe mixture contains mostly productsCORRECT
DThe forward and reverse reaction rates are both very slow
AI
Toaster Teacher
Why the answer is C, and why the others tempt you.
A large value of $K_c$ (much greater than 1) means the numerator (products) greatly exceeds the denominator (reactants) in the equilibrium expression, indicating that at equilibrium the mixture consists predominantly of products. A small $K_c$ would indicate mostly reactants. The magnitude of $K_c$ says nothing directly about the speed of the reaction.
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