What is a catalyst and how does it affect a reaction?

What is a catalyst and how does it affect a reaction?

• A. Solvent that changes temperature
• B. Product slows reaction
• C. Reactant consumed and slows rate
• D. Provides alternative route with lower activation energy; increases rate

Answer: (D)

A catalyst speeds up a reaction by offering an alternative route with a lower activation energy. Activation energy is the energy barrier that must be overcome for reactants to be converted into products. By providing a pathway that requires less energy to get over that barrier, more collisions at a given temperature are effective, so the rate constant increases and the reaction proceeds faster. The catalyst isn’t consumed in the overall reaction, so it can be reused, and it doesn’t change the overall amounts of reactants or products once equilibrium is reached. It may work by providing a surface or by changing the mechanism to a step that has a lower energy barrier, including enzymes as biological catalysts. The other ideas—being a solvent that simply changes temperature or a reactant or product that is consumed and slows the rate—don’t describe what a catalyst does.

A catalyst speeds up a reaction by offering an alternative route with a lower activation energy. Activation energy is the energy barrier that must be overcome for reactants to be converted into products. By providing a pathway that requires less energy to get over that barrier, more collisions at a given temperature are effective, so the rate constant increases and the reaction proceeds faster. The catalyst isn’t consumed in the overall reaction, so it can be reused, and it doesn’t change the overall amounts of reactants or products once equilibrium is reached. It may work by providing a surface or by changing the mechanism to a step that has a lower energy barrier, including enzymes as biological catalysts. The other ideas—being a solvent that simply changes temperature or a reactant or product that is consumed and slows the rate—don’t describe what a catalyst does.