16.1 Rate expression and reaction mechanism

A reaction proceeds by the following mechanism:

step 1: $\mathrm{A}+\mathrm{A}\to \mathrm{B}$
step 2: $\mathrm{B}+\mathrm{C}\to \mathrm{D}$

Which rate equation is consistent with this mechanism?

A.  Rate = k[B]²[C]

B.  Rate = k[A]²[B][C]

C.  Rate = k[A]²

D.  Rate = k[A][C]

A reaction proceeds by the following mechanism:

step 1: $\mathrm{A}+\mathrm{A}\to \mathrm{B}$
step 2: $\mathrm{B}+\mathrm{C}\to \mathrm{D}$

Which rate equation is consistent with this mechanism?

A.  Rate = k[B]²[C]

B.  Rate = k[A]²[B][C]

C.  Rate = k[A]²

D.  Rate = k[A][C]

Determine the rate expression for the reaction.

Determine the rate expression for the reaction.

Determine the rate expression for the reaction.

Calculate the rate constant of the reaction, stating its units.

Calculate the rate constant of the reaction, stating its units.

Calculate the rate constant of the reaction, stating its units.

The rate equation for a reaction is:

rate = k[A][B]

Which mechanism is consistent with this rate equation?

A.  2A $\rightleftharpoons$ I       Fast
     I + B → P    Slow

B.  A + B $\rightleftharpoons$ I   Fast
     I + A → P    Slow

C.  A → I          Slow
     I + B → P    Fast

D.  B $\rightleftharpoons$ I         Fast
     I + A → P    Slow

The rate equation for a reaction is:

rate = k[A][B]

Which mechanism is consistent with this rate equation?

A.  2A $\rightleftharpoons$ I       Fast
     I + B → P    Slow

B.  A + B $\rightleftharpoons$ I   Fast
     I + A → P    Slow

C.  A → I          Slow
     I + B → P    Fast

D.  B $\rightleftharpoons$ I         Fast
     I + A → P    Slow

Deduce the rate expression.

Deduce the rate expression.

Deduce the rate expression.

What is the activation energy according to the following plot of the linear form of the Arrhenius equation?

Arrhenius equation: $k=A{e}^{\frac{\mathit{-}Ea}{RT}}$.

A.  $E_a=\frac{2\times 8.31}{0.06}$

B.  $E_a=\frac{-2\times 8.31}{0.06}$

C.  $E_a=e^{\frac{2\times 8.31}{0.06}}$

D.  $E_a=e^{\frac{-2\times 8.31}{0.06}}$

What is the activation energy according to the following plot of the linear form of the Arrhenius equation?

Arrhenius equation: $k=A{e}^{\frac{\mathit{-}Ea}{RT}}$.

A.  $E_a=\frac{2\times 8.31}{0.06}$

B.  $E_a=\frac{-2\times 8.31}{0.06}$

C.  $E_a=e^{\frac{2\times 8.31}{0.06}}$

D.  $E_a=e^{\frac{-2\times 8.31}{0.06}}$

Deduce the rate expression for the reaction.

Deduce the rate expression for the reaction.

Deduce the rate expression for the reaction.

Two more trials (2 and 3) were carried out. The results are given below.

Determine the rate equation for the reaction and its overall order, using your answer from (b)(i).

Rate equation: 

Overall order: 

Two more trials (2 and 3) were carried out. The results are given below.

Determine the rate equation for the reaction and its overall order, using your answer from (b)(i).

Rate equation: 

Overall order: 

Two more trials (2 and 3) were carried out. The results are given below.

Determine the rate equation for the reaction and its overall order, using your answer from (b)(i).

Rate equation: 

Overall order: 

It has been suggested that the reaction occurs as a two-step process:

Step 1: N₂O (g) → N₂ (g) + O (g)

Step 2: N₂O (g) + O (g) → N₂ (g) + O₂ (g)

Explain how this could support the observed rate expression.

It has been suggested that the reaction occurs as a two-step process:

Step 1: N₂O (g) → N₂ (g) + O (g)

Step 2: N₂O (g) + O (g) → N₂ (g) + O₂ (g)

Explain how this could support the observed rate expression.

It has been suggested that the reaction occurs as a two-step process:

Step 1: N₂O (g) → N₂ (g) + O (g)

Step 2: N₂O (g) + O (g) → N₂ (g) + O₂ (g)

Explain how this could support the observed rate expression.

Data is given for the reaction 2X₂ (g) + Y₂ (g) → 2X₂Y (g).

What rate equation can be inferred from the data?

A.  Rate = k [X₂] [Y₂]

B.  Rate = k [X₂]² [Y₂]

C.  Rate = k [X₂]² [Y₂]⁰

D.  Rate = k [X₂]² [Y₂]²

Data is given for the reaction 2X₂ (g) + Y₂ (g) → 2X₂Y (g).

What rate equation can be inferred from the data?

A.  Rate = k [X₂] [Y₂]

B.  Rate = k [X₂]² [Y₂]

C.  Rate = k [X₂]² [Y₂]⁰

D.  Rate = k [X₂]² [Y₂]²

The activation energy of a reaction can be obtained from the rate constant, k, and the absolute temperature, $\text{T}$. Which graph of these quantities produces a straight line?

A.  k against $\text{T}$

B.  k against $\frac{1}{\text{T}}$

C.  ln k against $\text{T}$

D.  ln k against $\frac{1}{\text{T}}$

The activation energy of a reaction can be obtained from the rate constant, k, and the absolute temperature, $\text{T}$. Which graph of these quantities produces a straight line?

A.  k against $\text{T}$

B.  k against $\frac{1}{\text{T}}$

C.  ln k against $\text{T}$

D.  ln k against $\frac{1}{\text{T}}$

This reaction could proceed through either S_N1 or S_N2 mechanisms depending on the reaction conditions. Sketch a graph of the rate versus nucleophile concentration, [CN⁻], for each of the mechanisms.

This reaction could proceed through either S_N1 or S_N2 mechanisms depending on the reaction conditions. Sketch a graph of the rate versus nucleophile concentration, [CN⁻], for each of the mechanisms.

This reaction could proceed through either S_N1 or S_N2 mechanisms depending on the reaction conditions. Sketch a graph of the rate versus nucleophile concentration, [CN⁻], for each of the mechanisms.

The rate expression for the reaction X (g) + 2Y (g) → 3Z (g) is 

rate = k[X]⁰ [Y]²

By which factor will the rate of reaction increase when the concentrations of X and Y are both increased by a factor of 3?

A. 6

B. 9

C. 18

D. 27

The rate expression for the reaction X (g) + 2Y (g) → 3Z (g) is 

rate = k[X]⁰ [Y]²

By which factor will the rate of reaction increase when the concentrations of X and Y are both increased by a factor of 3?

A. 6

B. 9

C. 18

D. 27

State the rate expression for the reaction.

State the rate expression for the reaction.

State the rate expression for the reaction.

Deduce the rate expression for the reaction.

Deduce the rate expression for the reaction.

Deduce the rate expression for the reaction.

The rate expression for the reaction is: rate = k [NO]²[O₂].

2NO (g) + O₂ (g) → 2NO₂ (g)

Which mechanism is not consistent with this rate expression?

The rate expression for the reaction is: rate = k [NO]²[O₂].

2NO (g) + O₂ (g) → 2NO₂ (g)

Which mechanism is not consistent with this rate expression?

Deduce how the rate of reaction at t = 2 would compare to the initial rate.

Deduce how the rate of reaction at t = 2 would compare to the initial rate.

Deduce how the rate of reaction at t = 2 would compare to the initial rate.

Which statement is correct about a catalyst?

A. It decreases the activation energy of the forward reaction but not the reverse.

B. It increases the proportion of products to reactants in an equilibrium.

C. It decreases the enthalpy change of the reaction.

D. It changes the mechanism of the reaction.

Which statement is correct about a catalyst?

A. It decreases the activation energy of the forward reaction but not the reverse.

B. It increases the proportion of products to reactants in an equilibrium.

C. It decreases the enthalpy change of the reaction.

D. It changes the mechanism of the reaction.

What is the order with respect to each reactant?

2NO (g) + Cl₂ (g) → 2NOCl (g)

What is the order with respect to each reactant?

2NO (g) + Cl₂ (g) → 2NOCl (g)

Determine the rate expression from the results, explaining your method.

Determine the rate expression from the results, explaining your method.

Determine the rate expression from the results, explaining your method.

What are the units of the rate constant, $k$, if the rate equation is $\mathrm{Rate}=k\left[\mathrm{A}\right]{\left[\mathrm{B}\right]}^2$?

A.  $\mathrm{mol} {\mathrm{dm}}^{-3} {\mathrm{s}}^{-1}$

B.  ${\mathrm{dm}}^3 {\mathrm{mol}}^{-1 }{\mathrm{s}}^{-1}$

C.  ${\mathrm{dm}}^6 {\mathrm{mol}}^{-2 }{\mathrm{s}}^{-1}$

D.  ${\mathrm{dm}}^9 {\mathrm{mol}}^{-3 }{\mathrm{s}}^{-1}$

What are the units of the rate constant, $k$, if the rate equation is $\mathrm{Rate}=k\left[\mathrm{A}\right]{\left[\mathrm{B}\right]}^2$?

A.  $\mathrm{mol} {\mathrm{dm}}^{-3} {\mathrm{s}}^{-1}$

B.  ${\mathrm{dm}}^3 {\mathrm{mol}}^{-1 }{\mathrm{s}}^{-1}$

C.  ${\mathrm{dm}}^6 {\mathrm{mol}}^{-2 }{\mathrm{s}}^{-1}$

D.  ${\mathrm{dm}}^9 {\mathrm{mol}}^{-3 }{\mathrm{s}}^{-1}$

Which graph represents the relationship between the rate constant, $k$, and temperature, $T$, in kelvin?

Which graph represents the relationship between the rate constant, $k$, and temperature, $T$, in kelvin?

Write the rate expression for this reaction.

Write the rate expression for this reaction.

Write the rate expression for this reaction.

Calculate the value of the rate constant, k, giving its units.

Calculate the value of the rate constant, k, giving its units.

Calculate the value of the rate constant, k, giving its units.

Explain, using equations, how the presence of ${\text{CCl}}_{\text{2}}{\text{F}}_{\text{2}}$ results in a chain reaction that decreases the concentration of ozone in the stratosphere.

Explain, using equations, how the presence of ${\text{CCl}}_{\text{2}}{\text{F}}_{\text{2}}$ results in a chain reaction that decreases the concentration of ozone in the stratosphere.

Explain, using equations, how the presence of ${\text{CCl}}_{\text{2}}{\text{F}}_{\text{2}}$ results in a chain reaction that decreases the concentration of ozone in the stratosphere.

Determine the value and unit of the rate constant using the rate expression in (a).

Determine the value and unit of the rate constant using the rate expression in (a).

Determine the value and unit of the rate constant using the rate expression in (a).

Deduce the rate expression for this reaction.

Deduce the rate expression for this reaction.

Deduce the rate expression for this reaction.

Determine the initial rate of reaction in experiment 4.

Determine the initial rate of reaction in experiment 4.

Determine the initial rate of reaction in experiment 4.

What is correct about the rate of disappearance of NO?

2NO (g) + 2H₂(g) → N₂(g) + 2H₂O (g)

rate = k[H₂][NO]²

A.  It equals half the rate of disappearance of H₂.

B.  It equals the rate of disappearance of H₂.

C.  It equals twice the rate of disappearance of H₂.

D.  It equals four times the rate of disappearance of H₂.

What is correct about the rate of disappearance of NO?

2NO (g) + 2H₂(g) → N₂(g) + 2H₂O (g)

rate = k[H₂][NO]²

A.  It equals half the rate of disappearance of H₂.

B.  It equals the rate of disappearance of H₂.

C.  It equals twice the rate of disappearance of H₂.

D.  It equals four times the rate of disappearance of H₂.

Use the graph to deduce the dependence of the reaction rate on the amount of Mg.

Use the graph to deduce the dependence of the reaction rate on the amount of Mg.

Use the graph to deduce the dependence of the reaction rate on the amount of Mg.

The reaction is first order with respect to HCl. Calculate the time taken, in seconds (s), for half of the Mg to dissolve when [HCl] = 0.5 mol dm^–3.

The reaction is first order with respect to HCl. Calculate the time taken, in seconds (s), for half of the Mg to dissolve when [HCl] = 0.5 mol dm^–3.

The reaction is first order with respect to HCl. Calculate the time taken, in seconds (s), for half of the Mg to dissolve when [HCl] = 0.5 mol dm^–3.

Deduce the order of reaction with respect to hydrogen.

Deduce the order of reaction with respect to hydrogen.

Deduce the order of reaction with respect to hydrogen.

Calculate the value of the rate constant stating its units.

Calculate the value of the rate constant stating its units.

Calculate the value of the rate constant stating its units.

What is the enthalpy change for the following reaction?

CH₄ (g) + H₂O (g) → CO (g) + 3H₂ (g)

A.  −74 − 242 + 111

B.  +74 + 242 − 111

C.  −74 − 484 − 222

D.  +74 + 484 − 222

What is the enthalpy change for the following reaction?

CH₄ (g) + H₂O (g) → CO (g) + 3H₂ (g)

A.  −74 − 242 + 111

B.  +74 + 242 − 111

C.  −74 − 484 − 222

D.  +74 + 484 − 222