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A reaction between gases X and Y follows the rate law: Rate = k[X]²[Y]. If the concentration of X is tripled and the concentration of Y is halved, the new rate will be:
1.5 times the original rate
4.5 times the original rate
9 times the original rate
0.75 times the original rate
Two molecules A and B collide, but no reaction occurs. Which of the following MUST be true?
The molecules did not collide with the correct orientation.
The molecules are not reactive under any conditions.
The collision did not have sufficient energy to overcome the activation energy barrier.
The temperature of the system is too low for any reaction to occur.
For a reaction with an activation energy () of 50 kJ/mol, how much would a 10°C increase in temperature increase the rate constant, according to the Arrhenius equation (assuming ) at room temperature (approx. 300K)?
Approximately half
Approximately double
Approximately quadruple
Negligible change
A reaction proceeds via a two-step mechanism. The first step is a fast, reversible equilibrium with a small equilibrium constant. The second step is slow. Which of the following is MOST likely true about the overall reaction rate?
The overall rate will be determined solely by the rate of the slow step.
The overall rate will be independent of the concentration of the intermediate.
The overall rate will be dependent on the concentrations of the reactants in both steps.
The equilibrium constant of the first step will have no effect on the overall rate.
Which factor has the LEAST impact on the rate of a reaction involving large, complex biomolecules?
Presence of a catalyst
Substrate concentration
Temperature
Reactant molecular weight
The pre-exponential factor (A) in the Arrhenius equation is related to the:
Activation energy of the reaction
Enthalpy change of the reaction
Frequency of collisions with proper orientation
Temperature of the reaction
According to collision theory, which factor does NOT significantly affect the rate of a reaction?
The orientation of the colliding molecules
The kinetic energy of the colliding molecules
The frequency of collisions between molecules
The size of the reaction vessel
For a reaction to occur according to collision theory, the colliding molecules must have:
Energy less than the activation energy and proper orientation
Energy greater than or equal to the activation energy and any orientation
Energy less than the activation energy and any orientation
Energy greater than or equal to the activation energy and proper orientation
Increasing the temperature of a reaction generally increases the reaction rate. Which aspect of collision theory best explains this observation?
Increased temperature reduces the activation energy of the reaction.
Increased temperature changes the orientation of the colliding molecules.
Increased temperature decreases the frequency of collisions between molecules.
Increased kinetic energy of molecules leads to more collisions exceeding the activation energy.
Which statement best describes the relationship between activation energy and reaction rate?
Reactions with higher activation energies generally proceed faster.
Activation energy has no effect on reaction rate.
The relationship between activation energy and reaction rate is unpredictable.
Reactions with lower activation energies generally proceed faster.
