NEET Chemistry: Rate of reaction and rate law Practice Questions
11 free multiple-choice questions on Rate of reaction and rate law (Chemical Kinetics) for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. Which of the following physical quantities is used to express the rate of a chemical reaction?
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Correct answer: A — Change in concentration per unit time
The rate of reaction is defined as the change in the concentration of reactants or products per unit time. This is the fundamental definition used in chemical kinetics.
Q2. If the rate of reaction is zero, what does this imply about the concentration dependence of the rate law?
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Correct answer: C — The reaction rate is zero regardless of concentration.
If the rate of reaction is zero, it implies that the rate expression, which depends on concentration, evaluates to zero, indicating no reaction is occurring under those conditions.
Q3. The rate of a reaction is measured in terms of concentration change per second. If a reaction proceeds at a rate of 0.5 M/s, what is the unit of the rate of reaction?
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Correct answer: B — M/s
Concentration is in M (moles per liter), and time is in seconds. Therefore, the unit for the rate of reaction is M/s (or mol L⁻¹ s⁻¹).
Q4. Which term in the rate law is independent of the concentrations of the reactants?
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Correct answer: C — The rate constant (k).
The rate constant (k) is a temperature and concentration-dependent term that is independent of the instantaneous concentrations of the reactants themselves.
Q5. If the rate of a reaction is zero, what can be inferred about the rate law expression?
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Correct answer: D — The rate of reaction is zero if the concentration of one reactant is zero (assuming the order is positive).
If the rate law involves concentrations of reactants, setting the rate to zero implies that at least one reactant concentration must be zero, which stops the reaction.
Q6. If the rate constant (k) for a reaction remains constant, how does the rate of reaction change if the concentration of a reactant is doubled?
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Correct answer: C — It is doubled.
If Rate = k[A]ⁿ, doubling [A] while keeping k constant will result in the rate being multiplied by 2ⁿ. Assuming a simple first-order reaction (n=1), doubling the concentration doubles the rate.
Q7. For a general reaction aA + bB → Products, if the experimentally determined rate law is Rate = k[A]²[B]¹, what is the overall order of the reaction?
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Correct answer: B — 3
The order of the reaction is the sum of the exponents of the concentration terms in the experimentally determined rate law. Here, the order is 2 + 1 = 3.
Q8. What physical quantity has the same SI unit as the rate of a chemical reaction?
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Correct answer: A — mol · L⁻¹ · s⁻¹
The rate of reaction is the change in concentration per unit time (e.g., mol · L⁻¹ · s⁻¹), which is equivalent to molarity per second.
Q9. For a reaction 2A + B → C, if the rate law is determined to be Rate = k[A]¹[B]², what is the overall order of the reaction?
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Correct answer: C — 4
The order of the reaction is the sum of the exponents of the concentration terms in the rate law: 1 + 2 = 3.
Q10. For a generic elementary reaction A + B → Products, what is the expression for the rate law?
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Correct answer: B — Rate = k[A][B]
For an elementary reaction, the rate law is determined directly from the stoichiometry of the balanced equation. The rate is proportional to the product of the concentrations of the reactants raised to the power of their stoichiometric coefficients.
Q11. A reaction is classified as first order if the rate depends linearly on the concentration of one reactant. Which of the following correctly describes the rate dependency for a first-order reaction?
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Correct answer: D — Rate ∝ [Reactant]¹
For a first-order reaction, the rate law is Rate = k[Reactant]¹, meaning the rate is directly proportional to the concentration of the reactant raised to the power of 1.
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