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Rate of reaction

Chemistry • Reaction Rates • Knowledge-Based • 5 questions

Rate of reaction Knowledge-Based Download PDF

Chemistry · Chemical Kinetics · Chemistry · Reaction Rates

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

Questions

  1. 1.

    In chemical kinetics, why is a negative sign included in the mathematical expression for the rate of consumption of a reactant?

    • A) To yield a conventionally positive value for the reaction rate, since reactant concentration decreases over time.
    • B) To indicate that the reaction is thermodynamically spontaneous and proceeds in the forward direction.
    • C) To reflect that the average kinetic energy of the reacting particles declines during the reaction.
    • D) To show that the reaction is exothermic and transfers heat energy to the surrounding environment.
  2. 2.

    During the decomposition of nitrogen dioxide according to the equation 2NO2(g)→2NO(g)+O2(g)2\text{NO}_2(g) \rightarrow 2\text{NO}(g) + \text{O}_2(g), the concentration of NO2\text{NO}_2 decreases from 0.50 mol⋅L−10.50\text{ mol}\cdot\text{L}^{-1} to 0.32 mol⋅L−10.32\text{ mol}\cdot\text{L}^{-1} in 30 seconds30\text{ seconds}. What is the average rate of consumption of NO2\text{NO}_2 over this time interval?

    • A) 6.0×10−3 mol⋅L−1⋅s−16.0 \times 10^{-3}\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
    • B) 3.0×10−3 mol⋅L−1⋅s−13.0 \times 10^{-3}\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
    • C) 1.1×10−2 mol⋅L−1⋅s−11.1 \times 10^{-2}\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
    • D) 1.7×10−2 mol⋅L−1⋅s−11.7 \times 10^{-2}\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
  3. 3.

    Why does the reaction rate of a typical chemical reaction decrease as the reaction proceeds at constant temperature?

    • A) The concentrations of the reactants decrease over time, leading to less frequent collisions between reacting particles.
    • B) The activation energy of the reaction increases as products accumulate in the reaction mixture.
    • C) The rate constant of the reaction progressively decreases until the reactants are fully depleted.
    • D) The enthalpy change of the reaction diminishes continuously until molecular motion stops.
  4. 4.

    For a chemical reaction, how is the instantaneous rate of consumption of a reactant determined from a plot of its concentration versus time at a specific time t?

    • A) It is calculated from the total area under the curve between time zero and time t.
    • B) It is determined directly from the vertical intercept of the concentration-versus-time curve.
    • C) It is equal to the slope of the secant line connecting time zero and time t.
    • D) It is equal to the magnitude of the slope of the tangent line drawn to the curve at time t.
  5. 5.

    For the reaction 2N2O5(g)→4NO2(g)+O2(g)2\text{N}_2\text{O}_5(g) \rightarrow 4\text{NO}_2(g) + \text{O}_2(g), the rate of formation of NO2\text{NO}_2 is measured to be 0.048 mol⋅L−1⋅s−10.048\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1} at a given instant. What is the rate of consumption of N2O5\text{N}_2\text{O}_5 at this same instant?

    • A) 0.096 mol⋅L−1⋅s−10.096\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
    • B) 0.024 mol⋅L−1⋅s−10.024\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
    • C) 0.012 mol⋅L−1⋅s−10.012\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}
    • D) 0.048 mol⋅L−1⋅s−10.048\text{ mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}