$A$ catalyst added to a reaction mixture:

Assertion : The equilibrium constant is fixed and a characteristic for any given chemical reaction at a specified temperature.
Reason : The composition of the final equilibrium mixture at a particular temperature depends upon the starting amount of reactants.

For a reversible chemical reaction at equilibrium involving two reactants,if the concentrations of the reactants are doubled,what happens to the equilibrium constant $(K_c)$?

Predict which of the following reactions will have an appreciable concentration of both reactants and products:
$(a)$ $Cl_{2(g)} \longleftrightarrow 2Cl_{(g)};$ $K_{c}=5 \times 10^{-39}$
$(b)$ $Cl_{2(g)}+2NO_{(g)} \longleftrightarrow 2NOCl_{(g)};$ $K_{c}=3.7 \times 10^{8}$
$(c)$ $Cl_{2(g)}+2NO_{2(g)} \longleftrightarrow 2NO_{2}Cl_{(g)};$ $K_{c}=1.8$

Describe the method for measuring the equilibrium vapour pressure of water at a constant temperature.

At what change in Gibbs free energy $(\Delta G)$ does a reaction reach equilibrium?