A catalyst: I) lowers activation energy II) uses an existing reaction pathway III) is not consumed in the reaction and therefore does not appear in the chemical equation of eachmechanism IV) speeds up a reaction V) is homogeneous if it is in a different phase than the reactants

Consider the following hypothetical reaction coordinate diagram with stages represented by I, II, and III, and choose the true statement about the steps in the forward and reverse mechanisms. Which is a TRUE statement? a) Step II --> III is faster and less energetically favorable than step II -->I b) Step II --> III is faster and more energetically favorable than step II -->I c) Step II --> III is slower and less energetically favorable than step II -->I --> Ill is slower and more energetically favorable than | || ||| d) Step II step II -->I

The half-life of a chemical reaction is   the time it takes for half the present reactants to be used up   when a reaction has reached the half-way point   when only half of the reactant is used   the time passed when a reaction is half over

Catalysts increase reaction rates by _____ A) increasing the activation energy. B) increasing the enthalpy of reaction. C) decreasing the enthalpy of reaction. D) providing an alternate reaction mechanism with a lower activation energy. E) changing the value of the equilibrium constant.