Catalysis in Chemical Reactions
Chemistry ⇒ Chemical Kinetics and Equilibrium
Catalysis in Chemical Reactions starts at 11 and continues till grade 12.
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A reaction has an activation energy of 80 kJ/mol without a catalyst and 50 kJ/mol with a catalyst. By how much has the activation energy been lowered?
A reaction is catalyzed by an acid. Is this an example of homogeneous or heterogeneous catalysis?
Describe the difference between positive and negative catalysis.
Describe the effect of a catalyst on the rate of both the forward and reverse reactions in a reversible reaction.
Describe the effect of temperature on the activity of an enzyme catalyst.
Describe the main steps involved in heterogeneous catalysis according to the adsorption theory.
Describe the role of enzymes as biological catalysts.
Explain the difference between homogeneous and heterogeneous catalysis.
Explain the term 'catalyst poison' and give an example.
Explain why a catalyst does not affect the enthalpy change (ΔH) of a reaction.
Explain why increasing the surface area of a solid catalyst increases its effectiveness.
Explain why the presence of a catalyst does not affect the final concentrations of reactants and products at equilibrium.
The contact process for the manufacture of sulfuric acid uses vanadium(V) oxide as a catalyst. Is this an example of homogeneous or heterogeneous catalysis?
The decomposition of hydrogen peroxide is catalyzed by manganese dioxide. What type of catalysis is this?
A certain reaction is catalyzed by a solid catalyst. Over time, the rate of reaction decreases even though the reactant concentrations remain high. Suggest two possible reasons for the loss of catalytic activity and explain how each affects the catalyst.
A reaction has a rate constant k1 = 2.0 × 10−3 s−1 at 300 K without a catalyst. In the presence of a catalyst, the rate constant increases to k2 = 8.0 × 10−3 s−1 at the same temperature. Calculate the difference in activation energy (ΔEa) between the catalyzed and uncatalyzed reactions. (R = 8.314 J mol−1 K−1)
Consider the following reaction mechanism for the decomposition of ozone:
Step 1: O3 → O2 + O (slow)
Step 2: O3 + O → 2O2 (fast)
A catalyst X is introduced, which reacts with O3 in a new fast step to form an intermediate, lowering the activation energy of the overall reaction. Explain how the presence of catalyst X changes the reaction mechanism and the energy profile diagram.
Describe the role of promoters in heterogeneous catalysis and provide an example.
Explain, with reference to the transition state theory, how a catalyst affects the rate constant (k) of a reaction.
