Consider the reaction 2 NO2 (g) <=> N2O4

If the equilibrium concentration of both NO2 and N2O4 are 0.2 M, what is the value of Kc?

A. 0.2

B. 0.3

C. 0.225

D. 5.0

E. 2.5

Please help.

Which change will decrease the number of effective collisions during a chemical reaction? a. adding a catalyst b. increasing the surface area c. decreasing the temperature d. increasing the reactant concentrations e. increasing the volume of the reactants