Question 1

The ________ is the number of times that the reactants approach the activation barrier per unit time.

Accepted Answer

The frequency factor (also known as the pre-exponential factor) is the number of times that the reactants approach the activation barrier per unit time. It is an important factor in the Arrhenius equation, which describes the relationship between the rate of a reaction and its activation energy. The other answer choices are not relevant or accurate descriptions of this concept.

Question 2

Identify the rate-determining step.

Accepted Answer

The rate-determining step is the slowest step in a chemical reaction. This is because the overall rate of the reaction is limited by the speed of this step. The other steps may proceed quickly, but if the rate of the slowest step is slow, then the overall reaction rate will be slow as well.

Question 3

The second-order decomposition of NO₂ has a rate constant of 0.255 L mol^-1s^-1. How much NO₂ decomposes in 4.00 s if the initial concentration of NO₂ (1.00 L volume) is 1.33 mol L^-1?

Accepted Answer

The answer of The second-order decomposition of NO₂ has a...

Question 4

A reaction is found to have a rate constant of 3.36 × 10⁴ L mol^-1s^-1 at 344 K and a rate constant of 7.69 L mol^-1s^-1 at 219 K. Determine the activation energy for this reaction.

Accepted Answer

The Arrhenius equation can be used to link the rate constant with temperature: k = A exp(-Ea/RT) Rearranging the equation we get: ln(k) = ln(A) - Ea/RT Taking logarithms of both rate constants and subtracting those, we will obtain: ln(k2/k1) = ln(7.69/3.36) = 0.849 The activation energy is given by the slope of the line obtained when plotting ln(k) vs. 1/T. Using the two temperature values, we get: ln(k1) = ln(3.36 × 10⁴ L mol^-1s^-1) = 1.206 ln(k2) = ln(7.69 L mol^-1s^-1) = 2.039 Slope = -Ea/R = (-2.039 + 1.206)/(1/344 - 1/219) = 42.0 kJ mol^-1. Therefore, the correct answer is (B).

Question 5

Which rate law is bimolecular?

Accepted Answer

A bimolecular rate law contains two reactants raised to the first power. Choice B fits this requirement with [A] and [B] both raised to the first power.

Question 6

Calculate the frequency factor, A, for a reaction with a rate constant of 7834 s^-1 and an activation energy, E_a, of 68.4 kJ mol^-1 at 305 K.

Accepted Answer

The answer of Calculate the frequency factor, A, for a...

Question 7

For a reaction, what generally happens if the temperature is increased?

Accepted Answer

Increasing temperature generally results in an increase in the rate constant (k), which in turn leads to a faster reaction rate according to the Arrhenius equation.

Question 8

Calculate the frequency factor, A, for a reaction with a rate constant of 162.3 s^-1 and an activation energy, E_a, of 68 kJ mol^-1 at 298 K.

Accepted Answer

The frequency factor, A, can be calculated using the Arrhenius equation: k = A * e^(-Ea/RT). Rearranging for A gives A = k / e^(-Ea/RT). Substituting the given values (k = 162.3 s^-1, Ea = 68,000 J/mol, R = 8.314 J/mol·K, T = 298 K) results in A ≈ 1.3 × 10^14 s^-1.

Question 9

The ________ is the fraction of approaches that are successful in surmounting the activation barrier and forming products.

Accepted Answer

The exponential factor in the Arrhenius equation represents the fraction of molecules that have enough energy to overcome the activation energy barrier and form products.

Question 10

Calculate the frequency factor, A, for a reaction with a rate constant of 6.3 × 10³ s^-1 and an activation energy, E_a, of 74 kJ mol^-1 at 315 K.

Accepted Answer

The answer of Calculate the frequency factor, A, for a...

Question 11

If the activation energy for a given compound is found to be 42.0 kJ mol^-1 with a frequency factor of 8.0 × 10¹⁰ s^-1, what is the rate constant for this reaction at 298 K?

Accepted Answer

The answer of If the activation energy for a given...

Question 12

Which of the following reactions would you predict to have the smallest orientation factor?

Accepted Answer

The answer of Which of the following reactions would you...

Question 13

A reaction is found to have an activation energy of 108 kJ mol^-1. If the rate constant for this reaction is 4.60 × 10^-6 s^-1 at 275 K, what is the rate constant at 366 K?

Accepted Answer

The answer of A reaction is found to have an...

Question 14

What are the two key components of the frequency factor?

Accepted Answer

The frequency factor is defined as the number of successful collisions per unit time between reactant molecules. Its two key components are the orientation factor, which takes into account the geometric arrangement of the reactant molecules during collision, and the collision frequency, which considers the number of collisions per unit time. Activation energy and temperature are important factors in determining the rate constant, but they are not components of the frequency factor. The ideal gas constant is also not a component of the frequency factor.

Question 15

Which of the following statements is TRUE?

Accepted Answer

The rate constant of a reaction is dependent on temperature, and it increases with an increase in temperature. The rate constant is a measure of how fast a reaction occurs, and as the temperature increases, the molecules have more kinetic energy, which leads to more collisions and a higher rate of reaction. Therefore, the rate constant is only constant when the temperature remains constant.

Question 16

Which rate law is termolecular?

Accepted Answer

A termolecular reaction involves three reactant molecules. The rate law rate = k[A][B]^2 involves three molecules: one A and two B, making it termolecular.

Question 17

Which of the following reactions would you predict to have the largest orientation factor?

Accepted Answer

The answer of Which of the following reactions would you...

Question 18

The first-order rearrangement of CH₃NC is measured to have a rate constant of 3.61 × 10^-15 s^-1 at 298 K and a rate constant of 8.66 × 10^-7 s^-1 at 425 K. Determine the activation energy for this reaction.

Accepted Answer

The Arrhenius equation is:k = Ae^(-Ea/RT)where k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature.We can take the natural logarithm of both sides of the equation to get:ln(k) = ln(A) - (Ea/RT)If we plot ln(k) versus 1/T, we will get a straight line with a slope of -Ea/R.We can use the given data to plot the following graph:[Image of graph of ln(k) versus 1/T]The slope of the graph is -Ea/R = -160 kJ mol^-1.Therefore, the activation energy is 160 kJ mol^-1.

Question 19

A reaction is found to have an activation energy of 38.0 kJ mol^-1. If the rate constant for this reaction is 1.60 × 10² L mol^-1s^-1 at 249 K, what is the rate constant at 436 K?

Accepted Answer

The rate constant can be calculated using the Arrhenius equation: k2 = k1 * exp((Ea/R) * ((1/T2) - (1/T1))), where k1 = 1.60 × 10^12 L mol^-1 s^-1, Ea = 38.0 kJ mol^-1, R = 8.314 J K^-1 mol^-1, T1 = 249 K, and T2 = 436 K. Plugging in these values gives k2 = 4.20 × 10^15 L mol^-1 s^-1, which is closest to choice D.

Question 20

If the activation energy for a given compound is found to be 103 kJ mol^-1 with a frequency factor of 4.0 × 10¹³ s^-1, what is the rate constant for this reaction at 398 K?

Accepted Answer

The answer of If the activation energy for a given...

Quiz 13: Chemical Kinetics

The ________ is the number of times that the reactants approach the activation barrier per unit time.

Identify the rate-determining step.

The second-order decomposition of NO2 has a rate constant of 0.255 L mol-1 s-1. How much NO2 decomposes in 4.00 s if the initial concentration of NO2 (1.00 L volume) is 1.33 mol L-1?

A reaction is found to have a rate constant of 3.36 × 104 L mol-1 s-1 at 344 K and a rate constant of 7.69 L mol-1 s-1 at 219 K. Determine the activation energy for this reaction.

Which rate law is bimolecular?

Calculate the frequency factor, A, for a reaction with a rate constant of 7834 s-1 and an activation energy, Ea, of 68.4 kJ mol-1 at 305 K.