MCQ 61:
What does it mean if a reaction is described as being “at equilibrium”?
A) The concentrations of reactants and products are changing rapidly.
B) The rate of the forward reaction equals the rate of the reverse reaction.
C) No further reaction is occurring.
D) All reactants have been converted to products.
Answer: B) The rate of the forward reaction equals the rate of the reverse reaction.
Explanation: At equilibrium, the rates of the forward and reverse reactions are equal, leading to constant concentrations of reactants and products.
MCQ 62:
What type of reaction is characterized by the combination of two or more substances to form a single product?
A) Decomposition
B) Combustion
C) Synthesis
D) Replacement
Answer: C) Synthesis
Explanation: A synthesis reaction involves two or more reactants combining to form a single product.
MCQ 63:
Which of the following processes would likely increase the reaction rate of a solid reactant?
A) Reducing the temperature
B) Increasing the particle size
C) Increasing surface area
D) Adding a diluent
Answer: C) Increasing surface area
Explanation: Increasing the surface area of a solid reactant allows for more collisions with other reactants, thus increasing the reaction rate.
MCQ 64:
What happens to the reaction rate if a reactant is removed from the reaction mixture?
A) The rate increases.
B) The rate decreases.
C) The rate remains constant.
D) The reaction stops completely.
Answer: B) The rate decreases.
Explanation: Removing a reactant reduces the concentration of reactants available for collisions, leading to a decrease in the reaction rate.
MCQ 65:
The process by which a reaction reaches equilibrium can be described as:
A) A one-way process.
B) A dynamic process where reactants and products are formed at the same rate.
C) A spontaneous process that requires no energy input.
D) A process that occurs in a closed system only.
Answer: B) A dynamic process where reactants and products are formed at the same rate.
Explanation: At equilibrium, both the forward and reverse reactions occur simultaneously at the same rate, resulting in stable concentrations of reactants and products.
MCQ 66:
Which of the following is true about a reaction with a high activation energy?
A) It occurs quickly.
B) It is likely to be catalyzed.
C) It occurs spontaneously.
D) It has a low rate constant.
Answer: D) It has a low rate constant.
Explanation: A high activation energy typically results in a lower rate constant, meaning the reaction proceeds slowly under given conditions.
MCQ 67:
Which type of reaction involves the breakdown of a single compound into two or more products?
A) Combination
B) Decomposition
C) Displacement
D) Redox
Answer: B) Decomposition
Explanation: A decomposition reaction involves breaking down a single compound into two or more simpler products.
MCQ 68:
The principle that states that the rate of a chemical reaction is directly proportional to the concentration of the reactants is known as:
A) Le Chatelier’s Principle
B) Collision Theory
C) Rate Law
D) Hess’s Law
Answer: C) Rate Law
Explanation: The rate law describes the relationship between the rate of a chemical reaction and the concentration of reactants.
MCQ 69:
The overall order of a reaction is determined by:
A) The sum of the coefficients in the balanced equation.
B) The stoichiometry of the reaction.
C) The exponents in the rate law.
D) The activation energy of the reaction.
Answer: C) The exponents in the rate law.
Explanation: The overall order of a reaction is the sum of the powers (exponents) of the concentrations of reactants in the rate law.
MCQ 70:
If the rate of a reaction increases with temperature, this is generally due to:
A) A decrease in the frequency of collisions.
B) An increase in the average kinetic energy of the molecules.
C) A decrease in activation energy.
D) A change in the reaction mechanism.
Answer: B) An increase in the average kinetic energy of the molecules.
Explanation: Higher temperatures increase the kinetic energy of molecules, leading to more frequent and energetic collisions, thus increasing the reaction rate.
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