Which of the following statements about equilibrium constants are correct?

AAt a fixed temperature, $K_{c}$ for a reaction does not depend on the initial concentrations of reactants.
BAdding a catalyst increases the value of $K_{c}$ of a reaction.
CThe equilibrium constant of the reverse reaction is the reciprocal of that of the forward reaction.
DFor $C (s) + CO X_{2} (g) 2 CO (g)$ , $K_{c} = [CO]^{2} / [CO X_{2}]$ .

Answer: A, C, D

K_{c}

depends only on temperature, so (A) is true and (B) is false (a catalyst changes only the rate). Reversing the reaction inverts

K_{c}

, so (C) is true. Pure solid carbon is omitted from the expression, so (D) is true.