Which of the following is NOT a property of a catalyst?

• A. A catalyst lowers the free energy of the reactants
• B. A catalyst speeds up the reaction rate
• C. A catalyst provides an alternative reaction pathway
• D. A catalyst is not consumed in the reaction

Answer: (A)

The key idea is how a catalyst changes the energy landscape of a reaction. A catalyst works by providing an alternative pathway that has a lower activation energy, so more molecules can reach the transition state and the reaction proceeds faster. It does not change the overall free energy change of the reaction (ΔG); the starting energy of the reactants and the energy of the products stay the same, and the catalyst is not consumed in the process. Since lowering the free energy of the reactants would imply changing their intrinsic energy before the reaction even begins, that isn’t something a catalyst does. So the statement about lowering the free energy of the reactants is the one that isn’t true.