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Rate laws Knowledge-Based Practice

Chemistry · Chemical Kinetics · Chemistry · Reaction Rates

5 Chemistry practice questions on Rate laws. Questions that assess core concepts and understanding.

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Questions

  1. 1.

    A reaction follows the rate law Rate=k[NO]2[O2]\text{Rate} = k[\text{NO}]^2[\text{O}_2], with a rate constant k=2.5×103 M−2⋅s−1k = 2.5 \times 10^3\text{ M}^{-2}\cdot\text{s}^{-1}. What is the initial rate of the reaction when [NO]=0.020 M[\text{NO}] = 0.020\text{ M} and [O2]=0.010 M[\text{O}_2] = 0.010\text{ M}?

    • A) 5.0×10−1 M⋅s−15.0 \times 10^{-1}\text{ M}\cdot\text{s}^{-1}
    • B) 5.0×10−3 M⋅s−15.0 \times 10^{-3}\text{ M}\cdot\text{s}^{-1}
    • C) 1.0×10−4 M⋅s−11.0 \times 10^{-4}\text{ M}\cdot\text{s}^{-1}
    • D) 1.0×10−2 M⋅s−11.0 \times 10^{-2}\text{ M}\cdot\text{s}^{-1}
  2. 2.

    Which of the following statements is correct regarding the rate law and reaction orders for an overall chemical reaction?

    • A) The exponents in the rate law must equal the stoichiometric coefficients of the reactants in the overall balanced equation.
    • B) The rate law can be theoretically derived from the overall balanced equation without conducting experiments.
    • C) The overall reaction order is calculated by multiplying the stoichiometric coefficients of all reacting species.
    • D) The exponents in the rate law must be determined experimentally because they cannot be deduced from the overall balanced equation.
  3. 3.

    For the reaction A+B→C\text{A} + \text{B} \rightarrow \text{C}, doubling the initial concentration of A\text{A} quadruples the rate at constant [B][\text{B}], whereas doubling the initial concentration of B\text{B} produces no change in the rate at constant [A][\text{A}]. What is the experimentally determined rate law for this reaction?

    • A) Rate=k[A]2\text{Rate} = k[\text{A}]^2
    • B) Rate=k[A][B]\text{Rate} = k[\text{A}][\text{B}]
    • C) Rate=k[A]2[B]\text{Rate} = k[\text{A}]^2[\text{B}]
    • D) Rate=k[A][B]2\text{Rate} = k[\text{A}][\text{B}]^2
  4. 4.

    A chemical reaction follows the rate law Rate=k[X][Y]2\text{Rate} = k[\text{X}][\text{Y}]^2. What are the correct units of the rate constant kk if the concentration is measured in mol⋅L−1\text{mol}\cdot\text{L}^{-1} and time is measured in seconds?

    • A) s−1\text{s}^{-1}
    • B) L⋅mol−1⋅s−1\text{L}\cdot\text{mol}^{-1}\cdot\text{s}^{-1}
    • C) mol2⋅L−2⋅s−1\text{mol}^2\cdot\text{L}^{-2}\cdot\text{s}^{-1}
    • D) L2⋅mol−2⋅s−1\text{L}^2\cdot\text{mol}^{-2}\cdot\text{s}^{-1}
  5. 5.

    A chemical reaction follows the rate law Rate=k[A]2[B]\text{Rate} = k[\text{A}]^2[\text{B}]. By what factor will the initial reaction rate increase if the concentration of A\text{A} is tripled and the concentration of B\text{B} is doubled?

    • A) It increases by a factor of 6.
    • B) It increases by a factor of 18.
    • C) It increases by a factor of 12.
    • D) It increases by a factor of 36.

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