Factors affecting reaction rate Knowledge-Based Download PDF

Questions

1. 1.

   Which of the following statements best explains why precipitation reactions between aqueous ionic compounds generally occur almost instantaneously at room temperature, whereas reactions between covalent molecules often proceed much more slowly?

   • A) Dissolved ions possess significantly greater average kinetic energy than neutral covalent molecules at the same temperature.
   • B) Aqueous ions function as homogeneous catalysts that permanently lower the enthalpy change of the precipitation reaction.
   • C) Oppositely charged ions combine via electrostatic attraction without requiring the cleavage of strong covalent bonds.
   • D) Collisions between dissolved ions do not require a specific steric orientation to result in a chemical reaction.
2. 2.

   Which of the following best explains why grinding a solid reactant into a fine powder increases the rate of a heterogeneous chemical reaction?

   • A) It decreases the overall activation energy required for the reaction to occur.
   • B) It increases the average kinetic energy and speed of the solid particles.
   • C) It increases the exposed surface area, allowing a greater frequency of collisions between reactant particles.
   • D) It shifts the reaction equilibrium toward the formation of additional products.
3. 3.

   Which of the following statements best explains why an increase in temperature leads to a substantial increase in the rate of a chemical reaction?

   • A) It decreases the activation energy barrier required for the reaction to occur.
   • B) It increases the fraction of colliding particles that possess kinetic energy equal to or greater than the activation energy.
   • C) It shifts the reaction pathway to an alternative mechanism with a lower threshold energy.
   • D) It increases the orientation factor so that all collisions become geometrically effective.
4. 4.

   Which of the following statements correctly explains why increasing the concentration of a reactant increases the rate of a chemical reaction?

   • A) The frequency of collisions between reactant particles per unit volume increases.
   • B) The activation energy barrier of the reaction is lowered.
   • C) The average kinetic energy of the reacting particles increases.
   • D) The enthalpy change ($\Delta H$) of the overall reaction increases.
5. 5.

   Which of the following modifications will decrease the activation energy of a chemical reaction?

   • A) Increasing the temperature of the reaction mixture
   • B) Increasing the concentration of the reactants
   • C) Grinding a solid reactant into a fine powder
   • D) Adding a suitable catalyst to the system