Rates of Chemical Reactions
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Questions and Answers

What is the unit of the rate constant (kr) in the given reaction?

  • cm^3 mol^-1 s^-1
  • cm^3 molecule^-1 s^-1
  • dm^3 molecule^-1 s^-1
  • dm^3 mol^-1 s^-1 (correct)
  • What is the value of the rate constant (kr) in the given reaction?

  • 4.8 × 10^5 dm^3 mol^-1 s^-1 (correct)
  • 8.0 × 10^-18 dm^3 molecule^-1 s^-1
  • 2.0 × 10^-10 dm^3 mol^-1 s^-1
  • 8.0 × 10^-15 cm^3 molecule^-1 s^-1
  • What is the significance of knowing the rate law of a reaction?

  • It helps in understanding the mechanism of the reaction
  • It helps in predicting the rate of reaction from the composition of the mixture
  • It helps in understanding the kinetics of the reaction
  • All of the above (correct)
  • What is the advantage of knowing the value of the rate constant?

    <p>It helps in predicting the composition of the reaction mixture at a later stage</p> Signup and view all the answers

    What is the expression for the rate of reaction in terms of the formation of Br2?

    <p>d[Br2]/dt = 0.080 mmol dm^-3s^-1</p> Signup and view all the answers

    What is the unit of rate constant kr when the concentrations are expressed in mol dm⁻³?

    <p>mol² dm⁻¶ s⁻¹</p> Signup and view all the answers

    What is the overall order of the reaction with a rate law v = k [A]²[B]?

    <p>Third order</p> Signup and view all the answers

    What is the expression for the rate of consumption of NOBr?

    <p>-d[NOBr]/dt</p> Signup and view all the answers

    What is the unit of the rate of reaction v when the concentrations are expressed in mol dm⁻³ and the rate constant kr is in mol² dm⁻¶ s⁻¹?

    <p>mol dm⁻³ s⁻¹</p> Signup and view all the answers

    What is the relationship between the rate of reaction v and the rate of change of concentration of a reactant?

    <p>v = d[reactant]/dt / ν (reactant)</p> Signup and view all the answers

    What is the power to which the concentration of a reactant is raised in a rate law?

    <p>The order of reaction with respect to that reactant</p> Signup and view all the answers

    What is the order of the reaction with respect to H2 in the rate law for the reaction H2(g) + Br2(g) → 2 HBr(g)?

    <p>First order</p> Signup and view all the answers

    What is the characteristic of a zeroth-order rate law?

    <p>The rate is independent of the concentration of the reactant</p> Signup and view all the answers

    What is the significance of the rate law v = kr in the decomposition of phosphine (PH3)?

    <p>The reaction is zeroth order with respect to PH3</p> Signup and view all the answers

    What is the purpose of identifying the rate law and obtaining the rate constant from experimental data?

    <p>To understand the reaction kinetics</p> Signup and view all the answers

    What is the order of the reaction with respect to Br2 in the rate law for the reaction H2(g) + Br2(g) → 2 HBr(g)?

    <p>Indefinite order</p> Signup and view all the answers

    Why is it important to experimentally determine the rate law for a reaction?

    <p>To determine the reaction kinetics</p> Signup and view all the answers

    What is the significance of the rate law in the context of reaction kinetics?

    <p>It describes the reaction rate and its dependency on reactant concentrations</p> Signup and view all the answers

    What is the relationship between the rate law and the reaction order?

    <p>The reaction order determines the rate law</p> Signup and view all the answers

    What is the relationship between the most probable speed, c*, and the root mean square speed, c, of a molecule?

    <p>c* is always smaller than c</p> Signup and view all the answers

    What is the effect of increasing the temperature on the Maxwell distribution of molecular speeds?

    <p>The distribution becomes broader and shifts to the right</p> Signup and view all the answers

    What is the average speed of molecules in a gas, according to the Maxwell-Boltzmann distribution?

    <p>The mean speed, c̄</p> Signup and view all the answers

    What is the proportionality of the number of molecules at energy level E at temperature T?

    <p>proportional to exp(-E/kT)</p> Signup and view all the answers

    What is the significance of the pre-exponential factor, v^2, in the Maxwell-Boltzmann distribution?

    <p>It determines the fraction of molecules at very low speeds</p> Signup and view all the answers

    What is the relationship between the mean speed of two identical molecules, c̄, and the relative speed, c̄rel, at which they approach each other?

    <p>c̄rel is larger than c̄</p> Signup and view all the answers

    What is the normalization constant K in the Maxwell-Boltzmann distribution?

    <p>1 / (√(2πRT/M))³</p> Signup and view all the answers

    What is the distribution of speeds of molecules in a system at thermal equilibrium?

    <p>Maxwell distribution</p> Signup and view all the answers

    What is the most probable speed of molecules in a system at thermal equilibrium?

    <p>Zero</p> Signup and view all the answers

    What is the fraction of molecules that have speeds in a range of [v, v+dv] equal to?

    <p>f(v)dv</p> Signup and view all the answers

    What is the unit of the collision frequency z?

    <p>s⁻¹</p> Signup and view all the answers

    What is the mean free path λ in a gas?

    <p>The average distance a molecule travels between collisions</p> Signup and view all the answers

    What happens to the mean free path λ at constant volume when the temperature increases?

    <p>It remains the same</p> Signup and view all the answers

    What is the relation between the collision frequency z and the pressure p?

    <p>z ∝ p</p> Signup and view all the answers

    What is the value of the mean speed c̄rel for N₂ at 298 K and 100000 Pa?

    <p>475 m/s</p> Signup and view all the answers

    What is the relationship between the root mean square speed of the molecules and the temperature?

    <p>It is proportional to the square root of the temperature</p> Signup and view all the answers

    What is the difference between the root mean square speed and the average speed of the molecules?

    <p>The root mean square speed is always higher than the average speed</p> Signup and view all the answers

    What is the expression for the root mean square speed of the molecules?

    <p>c = √(3RT/M)</p> Signup and view all the answers

    What is the significance of the Maxwell-Boltzmann distribution?

    <p>It describes the distribution of speeds of molecules in a gas</p> Signup and view all the answers

    What is the relationship between the molar mass of a gas and the root mean square speed of its molecules?

    <p>Heavier molecules have a lower root mean square speed</p> Signup and view all the answers

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