Precision Paradox - Kinetic

Homogeneous vs. Heterogeneous Catalysis: : Identify the incorrect statement among the following

• Homogeneous catalysts and reactants exist in the same phase, which often leads to more uniform reaction conditions and rates.

• Heterogeneous catalysts act at the interface between different phases, often solid and liquid or gas, facilitating reactions without dissolving into the reaction mixture.

• Homogeneous catalysis is characterized by the catalyst existing in a solid phase separate from liquid or gaseous reactants, enhancing selectivity.

Catalysis and Activation Energy: : Identify the incorrect statement among the following

• Enzymes, as biological catalysts, reduce the activation energy required for biochemical reactions, thereby increasing reaction speed.

• Heterogeneous catalysts provide a surface on which reactants can adsorb, facilitating reactions that require lower activation energies.

• All catalysts increase the activation energy barrier for reactions, making them proceed more slowly but with greater specificity.

First-Order Reaction Plots: : Identify the incorrect statement among the following

• A plot of ln(concentration) versus time for a first-order reaction yields a straight line, with the slope equal to the negative rate constant.

• For first-order reactions, the half-life is constant and does not depend on the initial concentration of reactants.

• The graph of concentration versus time for a first-order reaction shows a parabolic curve, indicating a changing rate over time.

Catalysis: Identify the incorrect statement among the following

• Catalysts increase the rate of a chemical reaction by providing an alternative pathway with a lower activation energy.

• A catalyst remains chemically unchanged at the end of a reaction, meaning it does not appear in the overall chemical equation.

• Homogeneous catalysts operate in a different phase than the reactants, often leading to easier separation after the reaction.

Comparison of Plots for Third-Order Reactions: : Identify the incorrect statement among the following

• For a third-order reaction involving three reactants of the same concentration, the rate law is rate = k[A]^3, leading to complex kinetic behavior.

• The plot of ln(concentration) versus time for a third-order reaction shows a nonlinear relationship due to the cubic dependence on reactant concentration.

• A third-order reaction's concentration-time plot is a straight line, indicating a reaction rate that does not change with time.

Collision Theory: : Identify the incorrect statement among the following

• According to collision theory, the rate of a reaction is directly proportional to the number of effective collisions per unit time.

• For a collision to be effective, it must occur with sufficient energy and proper orientation to break existing bonds and form new ones.

• Collision theory suggests that increasing the concentration of reactants will decrease the number of effective collisions, reducing the reaction rate.

Effectiveness of Collisions: : Identify the incorrect statement among the following

• Increasing temperature generally increases the fraction of collisions with energy greater than the activation energy, thus increasing the reaction rate.

• The presence of a catalyst affects the collision frequency of molecules, significantly increasing the number of collisions per second.

• Effective collisions are those that result in the formation of products, which can be increased by lowering the reaction temperature.

Mechanism of Catalysis: : Identify the incorrect statement among the following

• Acid-base catalysis involves the transfer of protons between the catalyst and the substrate to lower the activation energy.

• In photocatalysis, light energy is used to activate the catalyst, which then increases the rate of the reaction by absorbing photons.

• Catalysis by transition metals involves the catalyst changing its oxidation state during the reaction, being consumed in the process.

Comparison of Plots for Zero-Order Reactions: : Identify the incorrect statement among the following

• A plot of concentration versus time for a zero-order reaction yields a straight line, indicating a constant rate of reaction.

• The slope of a plot for a zero-order reaction represents the negative rate constant, reflecting the decrease in reactant concentration over time.

• Zero-order reaction plots on a concentration-time graph curve upwards, showing acceleration of the reaction rate as time progresses.

Second-Order Reaction Plots: : Identify the incorrect statement among the following

• The plot of 1/concentration versus time for a second-order reaction shows a linear relationship, where the slope is proportional to the rate constant.

• Second-order reactions have a half-life that decreases with decreasing initial reactant concentrations.

• In second-order reactions, a plot of concentration versus time yields a straight line, indicating a constant reaction rate.