Question 1

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast:
A + 2B → C + D slow
A + C → E + F fast
What is the rate law predicted by this mechanism?

Accepted Answer

The rate law for a reaction mechanism is determined by the slow step, as it is the rate-determining step. In this case, the slow step is A + 2B → C + D, so the rate law is based on the concentrations of the reactants in this step, which are A and B. Since B is a reactant with a stoichiometric coefficient of 2, it appears squared in the rate law, leading to Rate = k[A][B]^2.

Question 2

One mechanism for the depletion of ozone in the stratosphere is proposed as follows: Cl + O₃ → ClO + O₂ ClO + O → Cl + O₂Identify any catalysts and intermediates in the reaction.

Accepted Answer

Cl acts as a catalyst because it is regenerated at the end of the reaction sequence, facilitating the reaction without being consumed. ClO is formed in the first step and consumed in the second, making it an intermediate.

Question 3

Which of the following statements is not a requirement for a valid reaction mechanism?

Accepted Answer

Each elementary reaction does not necessarily have to be bimolecular. It can be uni- or trimolecular as well.

Question 4

A mechanism that explains the rate law,Rate = k[(CH₃)₃CO₂C(CH₃)₃],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s)must be

Accepted Answer

The answer of A mechanism that explains the rate law,Rate...

Question 5

Given the following fast equilibrium (below)proposed for the gas phase reaction between NO and O₂,what is the expression for the equilibrium concentration of the intermediate NO₃? NO + O₂ NO₃

Accepted Answer

The answer of Given the following fast equilibrium (below)proposed for...

Question 6

Below is a proposed mechanism for the decomposition of H₂O₂. H₂O₂ + I^- → H₂O + IO^- Slow H₂O₂ + IO^- → H₂O + O₂ + I^- Fast Which of the following statements is incorrect?

Accepted Answer

The answer of Below is a proposed mechanism for the...

Question 7

Which of the following statements is incorrect?

Accepted Answer

The slow step in a mechanism can involve a two-body or a three-body collision, depending on the reaction mechanism. It is not necessarily always a three-body collision.

Question 8

The Arrhenius equation,  expresses the dependence of the rate constant on the reaction temperature.The slope of a plot of ln(k)versus 1/T is equal to

Accepted Answer

The answer of The Arrhenius equation,  expresses the dependence...

Question 9

The following mechanism has been suggested for the reaction between nitrogen monoxide and oxygen: NO(g)+ NO(g)→ N₂O₂(g)(fast) N₂O₂(g)+ O₂(g)→ 2NO₂(g)(slow) According to this mechanism,the experimental rate law is

Accepted Answer

The rate-determining step (slow step) dictates the rate law, which involves one molecule of N₂O₂ and one molecule of O2, making it first-order in each. However, since N₂O₂ is formed from 2 NO molecules in the fast step, the overall reaction is second-order in NO and first-order in O2.

Question 10

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast:
A + B → C + D slow
A + C → E + F fast
What is the net chemical equation predicted by this mechanism?

Accepted Answer

The net chemical equation is obtained by adding the two steps and canceling out the intermediates (species that appear on both sides of the equation). In this case, C is produced in the first step and consumed in the second, so it cancels out. The net equation is 2A + B → D + E + F, as A is consumed twice.

Question 11

The rate constants for the first-order decomposition of a compound are 5.22× 10^-4 s^-1 at 43°C and 2.91 × 10^-3 s^-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K))

Accepted Answer

We can use the Arrhenius equation to solve for the activation energy (Ea):

$k = Ae^{-Ea/RT}$

Taking the natural logarithm of both sides:

ln($k$) = ln($A$) - $\frac{Ea}{RT}$

We can set up two equations using the given rate constants and temperatures:

ln($k_1$) = ln($A$) - $\frac{Ea}{R(316)}$

ln($k_2$) = ln($A$) - $\frac{Ea}{R(335)}$

where $k_1$ and $k_2$ are the rate constants at 43°C and 62°C, respectively.

Solving for ln($A$) by subtracting the second equation from the first:

ln($k_1$) - ln($k_2$) = $\frac{Ea}{R}(\frac{1}{T_2} - \frac{1}{T_1})$

Plugging in the given values and solving for Ea:

ln(5.22x10^-14) - ln(2.91x10^-13) = $\frac{Ea}{8.31}(1/335 - 1/316)$

Ea = 79.5 kJ/mol

Therefore, the answer is D.

Question 12

A proposed mechanism for the decomposition of N₂O₅ is as follows: N₂O₅ NO₂ + NO₃ Slow step NO₂ + NO₃ NO₂ + O₂ + NO Fast step NO + N₂O₅ 3NO₂ Fast step What is the rate law predicted by this mechanism?

Accepted Answer

The answer of A proposed mechanism for the decomposition of...

Question 13

A proposed mechanism for the decomposition of N₂O₅ is as follows: N₂O₅ NO₂ + NO₃ Slow step NO₂ + NO₃ NO₂ + O₂ + NO Fast step NO + N₂O₅ 3NO₂ Fast step What is the overall chemical equation predicted by this mechanism?

Accepted Answer

The answer of A proposed mechanism for the decomposition of...

Question 14

For the elementary reaction A + B → C + D,what is the predicted rate law?

Accepted Answer

The reaction is a simple elementary reaction with only two reactants, so the rate law is expected to be directly proportional to the concentrations of both reactants. Therefore, the best choice is B: Rate = k[A][B].

Question 15

Determine the molecularity of the following elementary reaction: O₃ → O₂ + O.

Accepted Answer

The molecularity of a reaction refers to the number of molecules or species that must collide to produce the reaction. In the given elementary reaction, a single species breaks down into two products, indicating that the reaction is unimolecular.

Question 16

The rate constant for a reaction at 40.0°C is exactly 5 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.

Accepted Answer

The Arrhenius equation is given by:

k = A * exp(-Ea/RT)

where:
k = rate constant
A = pre-exponential factor
Ea = activation energy
R = gas constant (8.314 J/mol/K)
T = temperature in Kelvin

Let's call the rate constant at 20°C k1 and the rate constant at 40°C k2. According to the problem, we have:

k2 = 5 * k1

We can use the Arrhenius equation at both temperatures and divide the equations to eliminate A:

k2/k1 = exp[(Ea/R) * (1/T1 - 1/T2)]

5 = exp[(Ea/8.314) * (1/293 - 1/313)]
5 = exp[(Ea/8.314) * (-0.0068)]
ln(5) = -0.0068(Ea/8.314)
Ea = -ln(5) * 8.314 / 0.0068
Ea ≈ 61.4 kJ/mol

Therefore, the answer is C.

Question 17

For the first-order reaction 1/2 N₂O₄(g)→ NO₂(g); ΔH = 28.6 kJ The rate constant is k = 3.24 × 10⁵ s^-1 at -7°C,and the activation energy is 53.7 kJ/mol.What is the rate constant at 26°C?

Accepted Answer

The rate constant increases with temperature.

Question 18

A possible mechanism for the gas phase reaction of NO and H₂ is as follows: Step 1 2NO N₂O₂ Step 2 N₂O₂ + H₂ N₂O + H₂O Step 3 N₂O + H₂ N₂ + H₂O Which of the following statements concerning this mechanism is not directly supported by the information provided?

Accepted Answer

The answer of A possible mechanism for the gas phase...

Question 19

The decomposition of ozone may occur through the two-step mechanism shown below: Step 1 O₃ → O₂ + O Step 2 O₃ + O → 2O₂ The oxygen atom is considered to be a(n)

Accepted Answer

The oxygen atom is involved in both steps of the reaction but is not present in the final products. Therefore, it is classified as a reaction intermediate, which is a species that is formed in one step and consumed in a subsequent step of a reaction mechanism.

Question 20

The reaction CHCl₃(g)+ Cl₂(g) CCl₄(g)+ HCl(g)has been proposed to occur by the following mechanism. Cl₂ 2Cl fast equilibrium CHCl₃ + Cl HCl + CCl₃ slow step CCl₃ + Cl CCl₄ fast What is the rate law predicted by this mechanism?

Accepted Answer

The answer of The reaction CHCl₃(g)+ Cl₂(g) CCl₄(g)+ HCl(g)has...

Quiz 13: Rates of Reaction

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast: A + 2B → C + D slow A + C → E + F fast What is the rate law predicted by this mechanism?

One mechanism for the depletion of ozone in the stratosphere is proposed as follows: Cl + O₃ → ClO + O₂ ClO + O → Cl + O₂Identify any catalysts and intermediates in the reaction.

Which of the following statements is not a requirement for a valid reaction mechanism?

A mechanism that explains the rate law,Rate = k[(CH₃) ₃CO₂C(CH₃) ₃],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s) must be

Given the following fast equilibrium (below) proposed for the gas phase reaction between NO and O₂,what is the expression for the equilibrium concentration of the intermediate NO₃? NO + O₂ NO₃

Below is a proposed mechanism for the decomposition of H₂O₂. H₂O₂ + I^- → H₂O + IO^- Slow H₂O₂ + IO^- → H₂O + O₂ + I^- Fast Which of the following statements is incorrect?

Which of the following statements is incorrect?

The Arrhenius equation, expresses the dependence of the rate constant on the reaction temperature.The slope of a plot of ln(k) versus 1/T is equal to

The following mechanism has been suggested for the reaction between nitrogen monoxide and oxygen: NO(g) + NO(g) → N₂O₂(g) (fast) N₂O₂(g) + O₂(g) → 2NO₂(g) (slow) According to this mechanism,the experimental rate law is

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast: A + B → C + D slow A + C → E + F fast What is the net chemical equation predicted by this mechanism?

The rate constants for the first-order decomposition of a compound are 5.22× 10^-4 s^-1 at 43°C and 2.91 × 10^-3 s^-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K) )

A proposed mechanism for the decomposition of N₂O₅ is as follows: N₂O₅ NO₂ + NO₃ Slow step NO₂ + NO₃ NO₂ + O₂ + NO Fast step NO + N₂O₅ 3NO₂ Fast step What is the rate law predicted by this mechanism?

A proposed mechanism for the decomposition of N₂O₅ is as follows: N₂O₅ NO₂ + NO₃ Slow step NO₂ + NO₃ NO₂ + O₂ + NO Fast step NO + N₂O₅ 3NO₂ Fast step What is the overall chemical equation predicted by this mechanism?

For the elementary reaction A + B → C + D,what is the predicted rate law?

Determine the molecularity of the following elementary reaction: O₃ → O₂ + O.

The rate constant for a reaction at 40.0°C is exactly 5 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.

For the first-order reaction 1/2 N₂O₄(g) → NO₂(g) ; ΔH = 28.6 kJ The rate constant is k = 3.24 × 10⁵ s^-1 at -7°C,and the activation energy is 53.7 kJ/mol.What is the rate constant at 26°C?

A possible mechanism for the gas phase reaction of NO and H₂ is as follows: Step 1 2NO N₂O₂ Step 2 N₂O₂ + H₂ N₂O + H₂O Step 3 N₂O + H₂ N₂ + H₂O Which of the following statements concerning this mechanism is not directly supported by the information provided?

The decomposition of ozone may occur through the two-step mechanism shown below: Step 1 O₃ → O₂ + O Step 2 O₃ + O → 2O₂ The oxygen atom is considered to be a(n)

The reaction CHCl₃(g) + Cl₂(g) CCl₄(g) + HCl(g) has been proposed to occur by the following mechanism. Cl₂ 2Cl fast equilibrium CHCl₃ + Cl HCl + CCl₃ slow step CCl₃ + Cl CCl₄ fast What is the rate law predicted by this mechanism?

Quiz 13: Rates of Reaction

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast: A + 2B → C + D slow A + C → E + F fast What is the rate law predicted by this mechanism?

One mechanism for the depletion of ozone in the stratosphere is proposed as follows: Cl + O3 → ClO + O2 ClO + O → Cl + O2 Identify any catalysts and intermediates in the reaction.

Which of the following statements is not a requirement for a valid reaction mechanism?

A mechanism that explains the rate law,Rate = k[(CH3) 3CO2C(CH3) 3],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s) must be

Given the following fast equilibrium (below) proposed for the gas phase reaction between NO and O2,what is the expression for the equilibrium concentration of the intermediate NO3? NO + O2 NO3

Below is a proposed mechanism for the decomposition of H2O2. H2O2 + I- → H2O + IO- Slow H2O2 + IO- → H2O + O2 + I- Fast Which of the following statements is incorrect?

Which of the following statements is incorrect?

The Arrhenius equation, expresses the dependence of the rate constant on the reaction temperature.The slope of a plot of ln(k) versus 1/T is equal to

The following mechanism has been suggested for the reaction between nitrogen monoxide and oxygen: NO(g) + NO(g) → N2O2(g) (fast) N2O2(g) + O2(g) → 2NO2(g) (slow) According to this mechanism,the experimental rate law is

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast: A + B → C + D slow A + C → E + F fast What is the net chemical equation predicted by this mechanism?

The rate constants for the first-order decomposition of a compound are 5.22× 10-4 s-1 at 43°C and 2.91 × 10-3 s-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K) )

A proposed mechanism for the decomposition of N2O5 is as follows: N2O5 NO2 + NO3 Slow step NO2 + NO3 NO2 + O2 + NO Fast step NO + N2O5 3NO2 Fast step What is the rate law predicted by this mechanism?

A proposed mechanism for the decomposition of N2O5 is as follows: N2O5 NO2 + NO3 Slow step NO2 + NO3 NO2 + O2 + NO Fast step NO + N2O5 3NO2 Fast step What is the overall chemical equation predicted by this mechanism?

For the elementary reaction A + B → C + D,what is the predicted rate law?

Determine the molecularity of the following elementary reaction: O3 → O2 + O.

The rate constant for a reaction at 40.0°C is exactly 5 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.

For the first-order reaction 1/2 N2O4(g) → NO2(g) ; ΔH = 28.6 kJ The rate constant is k = 3.24 × 105 s-1 at -7°C,and the activation energy is 53.7 kJ/mol.What is the rate constant at 26°C?

A possible mechanism for the gas phase reaction of NO and H2 is as follows: Step 1 2NO N2O2 Step 2 N2O2 + H2 N2O + H2O Step 3 N2O + H2 N2 + H2O Which of the following statements concerning this mechanism is not directly supported by the information provided?

The decomposition of ozone may occur through the two-step mechanism shown below: Step 1 O3 → O2 + O Step 2 O3 + O → 2O2 The oxygen atom is considered to be a(n)

The reaction CHCl3(g) + Cl2(g) CCl4(g) + HCl(g) has been proposed to occur by the following mechanism. Cl2 2Cl fast equilibrium CHCl3 + Cl HCl + CCl3 slow step CCl3 + Cl CCl4 fast What is the rate law predicted by this mechanism?

One mechanism for the depletion of ozone in the stratosphere is proposed as follows: Cl + O₃ → ClO + O₂ ClO + O → Cl + O₂Identify any catalysts and intermediates in the reaction.

A mechanism that explains the rate law,Rate = k[(CH₃) ₃CO₂C(CH₃) ₃],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s) must be

Given the following fast equilibrium (below) proposed for the gas phase reaction between NO and O₂,what is the expression for the equilibrium concentration of the intermediate NO₃? NO + O₂ NO₃

Below is a proposed mechanism for the decomposition of H₂O₂. H₂O₂ + I^- → H₂O + IO^- Slow H₂O₂ + IO^- → H₂O + O₂ + I^- Fast Which of the following statements is incorrect?

The following mechanism has been suggested for the reaction between nitrogen monoxide and oxygen: NO(g) + NO(g) → N₂O₂(g) (fast) N₂O₂(g) + O₂(g) → 2NO₂(g) (slow) According to this mechanism,the experimental rate law is

The rate constants for the first-order decomposition of a compound are 5.22× 10^-4 s^-1 at 43°C and 2.91 × 10^-3 s^-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K) )

A proposed mechanism for the decomposition of N₂O₅ is as follows: N₂O₅ NO₂ + NO₃ Slow step NO₂ + NO₃ NO₂ + O₂ + NO Fast step NO + N₂O₅ 3NO₂ Fast step What is the rate law predicted by this mechanism?

A proposed mechanism for the decomposition of N₂O₅ is as follows: N₂O₅ NO₂ + NO₃ Slow step NO₂ + NO₃ NO₂ + O₂ + NO Fast step NO + N₂O₅ 3NO₂ Fast step What is the overall chemical equation predicted by this mechanism?

Determine the molecularity of the following elementary reaction: O₃ → O₂ + O.

For the first-order reaction 1/2 N₂O₄(g) → NO₂(g) ; ΔH = 28.6 kJ The rate constant is k = 3.24 × 10⁵ s^-1 at -7°C,and the activation energy is 53.7 kJ/mol.What is the rate constant at 26°C?

A possible mechanism for the gas phase reaction of NO and H₂ is as follows: Step 1 2NO N₂O₂ Step 2 N₂O₂ + H₂ N₂O + H₂O Step 3 N₂O + H₂ N₂ + H₂O Which of the following statements concerning this mechanism is not directly supported by the information provided?

The decomposition of ozone may occur through the two-step mechanism shown below: Step 1 O₃ → O₂ + O Step 2 O₃ + O → 2O₂ The oxygen atom is considered to be a(n)

The reaction CHCl₃(g) + Cl₂(g) CCl₄(g) + HCl(g) has been proposed to occur by the following mechanism. Cl₂ 2Cl fast equilibrium CHCl₃ + Cl HCl + CCl₃ slow step CCl₃ + Cl CCl₄ fast What is the rate law predicted by this mechanism?