Question 1

For a chemical reaction,the activation energy for the forward reaction is +181 kJ and the activation energy for the backward reaction is +62 kJ.What is the net energy change for the forward reaction?

Accepted Answer

The net energy change for a reaction is given by the difference in energy between the products and the reactants, which is equal to the energy released in the forward reaction minus the energy absorbed in the backward reaction.

Since the activation energy for the forward reaction is higher than the activation energy for the backward reaction, we know that the forward reaction is endothermic (requires energy input), while the backward reaction is exothermic (releases energy).

Therefore, the net energy change for the forward reaction is given by:

Net energy change = energy released in the forward reaction - energy absorbed in the backward reaction

Net energy change = (-181 kJ) - (+62 kJ)
Net energy change = -119 kJ

Since the net energy change is negative, this means that the forward reaction is endothermic and requires an input of energy. The correct answer is therefore (C) +119 kJ, which represents the energy that needs to be absorbed in order for the forward reaction to take place.

Question 2

The reaction,A + 2B → B₂ + A,proceeds by the following mechanism: (A is a catalyst.) A + B → AB (slow) AB + B → B₂ + A (fast) What is the rate law expression for this reaction?

Accepted Answer

The rate law is determined by the slowest step in the mechanism, which is the first step in this case. The rate law expression for the first step is Rate=k[A][B], so the overall rate law expression for the reaction is also Rate=k[A][B].

Question 3

Consider the following proposed mechanism.If this mechanism for the overall reaction were correct,and if k₁ were much less than k₂,then the observed rate law would be 2A C + I I + B C + D

Accepted Answer

The answer of Consider the following proposed mechanism.If this mechanism...

Question 4

Calculate the activation energy,E_a,for N₂O₅(g)→ 2 NO₂(g)+ 1/2 O₂(g) Given k (at 45.0 °C)= 5.79 × 10^-4 s^-1 and k (at 60.0 °C)= 3.83 × 10^-3 s^-1.(R = 8.314 J/K⋅mol)

Accepted Answer

The activation energy can be calculated using the Arrhenius equation: ln(k2/k1) = (Ea/R) * (1/T1 - 1/T2). Converting temperatures to Kelvin and substituting the given values, Ea is approximately 111 kJ/mol.

Question 5

Nitrogen dioxide reacts with carbon monoxide to produce nitrogen monoxide and carbon dioxide. NO₂(g)+ CO(g)→ NO(g)+ CO₂(g) A proposed mechanism for this reaction is 2 NO₂(g) NO₃(g)+ NO(g) (fast,equilibrium) NO₃(g)+ CO(g)→ NO₂(g)+ CO₂(g) (slow) What is a rate law that is consistent with the proposed mechanism?

Accepted Answer

The answer of Nitrogen dioxide reacts with carbon monoxide to...

Question 6

The rate constant for a first-order reaction is 1.7 × 10^-2 s^-1 at 676 K and 3.9 × 10^-2 s^-1 at 880 K.Determine the activation energy of the reaction.(R = 8.314 J/K⋅mol)

Accepted Answer

The answer of The rate constant for a first-order reaction...

Question 7

Molecules must overcome a barrier called the activation energy if they are to react.The highest energy point reached during the progress of a reaction is called the ____.

Accepted Answer

The highest energy point reached during the progress of a reaction is called the transition state. This is the point where the reactants are most unstable and have the highest energy, and where the reaction is most likely to either proceed to form products or revert back to reactants.

Question 8

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

IO^- is not a catalyst as it is consumed in the first step of the mechanism and thus is a reactant. A catalyst is a substance that facilitates a chemical reaction without itself being consumed in the reaction.

Question 9

Which of the following is the effect of adding a catalyst to a reaction?

Accepted Answer

A catalyst lowers the activation energy of a reaction, which means that the reaction can occur more easily and with less energy. This results in an increase in the rate of reaction without changing the equilibrium constant or the enthalpy change of the reaction. The catalyst itself is not consumed in the reaction and does not affect the yield of products.

Question 10

A suggested mechanism for the decomposition of ozone is as follows: O₃ O₂ + O fast equilibrium O + O₃ 2O₂ slow step What is the rate law predicted by this mechanism?

Accepted Answer

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

Question 11

For the formation of 1 mol of nitrosyl chloride at a given temperature,Δ_rH = -37 kJ/mol. NO(g)+ ½ Cl₂(g)→ NOCl(g) The activation energy for this reaction is 81 kJ/mol.What is the activation energy for the reverse reaction?

Accepted Answer

The activation energy for the reverse reaction can be found by adding the enthalpy change of the reaction (ΔH) to the activation energy of the forward reaction. Given ΔH = -37 kJ/mol and the activation energy for the forward reaction is 81 kJ/mol, the activation energy for the reverse reaction is 81 kJ/mol - (-37 kJ/mol) = 118 kJ/mol.

Question 12

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 13

In a reaction coordinate diagram,reacting molecules are most unstable ______.

Accepted Answer

The transition state represents the highest point on the reaction coordinate diagram, where the reacting molecules are in the process of breaking and forming new bonds. At this point, the system is most unstable and has the highest energy. Therefore, option D is the correct choice.

Question 14

The rate constant at 366 K for a first-order reaction is 7.7 × 10^-3 s^-1 and the activation energy is 15.9 kJ/mol.What is the value of the frequency factor,A,in the Arrhenius equation? (R = 8.314 J/K⋅mol)

Accepted Answer

The Arrhenius equation is k = A * e^(-Ea/(RT)). Rearranging for A gives A = k / e^(-Ea/(RT)). Substituting the given values (k = 7.7 × 10^-3 s^-1, Ea = 15.9 kJ/mol = 15900 J/mol, R = 8.314 J/K⋅mol, T = 366 K) into the equation gives A ≈ 1.4 s^-1.

Question 15

For the overall reaction A + 2B → C,which of the following mechanisms yields the correct overall chemical equation and is consistent with the rate equation below? Rate = k[A][B]

Accepted Answer

In the rate equation, the rate is proportional to the concentration of both reactants A and B. This indicates that both A and B must be involved in the rate-determining step. Option B shows a mechanism in which both reactants A and B are involved in the slow step, and it yields the correct overall chemical equation as well. Therefore, option B is the best choice.

Question 16

The reaction kinetics for a certain reaction are studied over several temperatures.Which of the following is/are not effected by a change in reaction temperature?

Accepted Answer

The energy of activation, E_a, is not affected by a change in reaction temperature. It is a constant characteristic of the specific reaction and remains the same regardless of changes in temperature. The reaction rate and rate constant are both affected by changes in temperature.

Question 17

A catalyst ____.

Accepted Answer

A catalyst lowers the activation energy required for a chemical reaction to occur, making the reaction proceed faster or at a lower temperature, but it is not consumed or changed in the reaction.

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 rate constant for a reaction at 40.0°C is exactly 6 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.(R = 8.314 J/K⋅mol)

Accepted Answer

Using the Arrhenius equation, k = A * exp(-Ea/(RT)), and the given information that k2/k1 = 6, we can set up the equation: ln(6) = Ea/R * (1/T1 - 1/T2). Substituting T1 = 293 K and T2 = 313 K, and solving for Ea gives approximately 68.3 kJ/mol.

Question 20

For the overall reaction 2A + B → C Which of the following mechanisms is/are consistent with a rate equation of rate = k[A]²[B]?

Accepted Answer

The rate equation suggests that the reaction is second order with respect to A (^{2) and zero order with respect to B (}). Option A involves a fast step with I as an intermediate, which is consistent with the rate equation. Option D also has a fast step but involves a different intermediate. Therefore, options A and D are both possible mechanisms. Hence, the correct answer is choice E, which includes both options A and D.

Quiz 15: Chemical Kinetics: the Rates of Chemical Reactions

For a chemical reaction,the activation energy for the forward reaction is +181 kJ and the activation energy for the backward reaction is +62 kJ.What is the net energy change for the forward reaction?

The reaction,A + 2B → B₂ + A,proceeds by the following mechanism: (A is a catalyst.) A + B → AB (slow) AB + B → B₂ + A (fast) What is the rate law expression for this reaction?

Consider the following proposed mechanism.If this mechanism for the overall reaction were correct,and if k₁ were much less than k₂,then the observed rate law would be 2A C + I I + B C + D

Calculate the activation energy,E_a,for N₂O₅(g) → 2 NO₂(g) + 1/2 O₂(g) Given k (at 45.0 °C) = 5.79 × 10^-4 s^-1 and k (at 60.0 °C) = 3.83 × 10^-3 s^-1.(R = 8.314 J/K⋅mol)

The rate constant for a first-order reaction is 1.7 × 10^-2 s^-1 at 676 K and 3.9 × 10^-2 s^-1 at 880 K.Determine the activation energy of the reaction.(R = 8.314 J/K⋅mol)

Molecules must overcome a barrier called the activation energy if they are to react.The highest energy point reached during the progress of a reaction is called the ____.

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 is the effect of adding a catalyst to a reaction?

A suggested mechanism for the decomposition of ozone is as follows: O₃ O₂ + O fast equilibrium O + O₃ 2O₂ slow step What is the rate law predicted by this mechanism?

For the formation of 1 mol of nitrosyl chloride at a given temperature,Δ_rH = -37 kJ/mol. NO(g) + ½ Cl₂(g) → NOCl(g) The activation energy for this reaction is 81 kJ/mol.What is the activation energy for the reverse reaction?

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

In a reaction coordinate diagram,reacting molecules are most unstable ______.

The rate constant at 366 K for a first-order reaction is 7.7 × 10^-3 s^-1 and the activation energy is 15.9 kJ/mol.What is the value of the frequency factor,A,in the Arrhenius equation? (R = 8.314 J/K⋅mol)

For the overall reaction A + 2B → C,which of the following mechanisms yields the correct overall chemical equation and is consistent with the rate equation below? Rate = k[A][B]

The reaction kinetics for a certain reaction are studied over several temperatures.Which of the following is/are not effected by a change in reaction temperature?

A catalyst ____.

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 rate constant for a reaction at 40.0°C is exactly 6 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.(R = 8.314 J/K⋅mol)

For the overall reaction 2A + B → C Which of the following mechanisms is/are consistent with a rate equation of rate = k[A]²[B]?

Quiz 15: Chemical Kinetics: the Rates of Chemical Reactions

For a chemical reaction,the activation energy for the forward reaction is +181 kJ and the activation energy for the backward reaction is +62 kJ.What is the net energy change for the forward reaction?

The reaction,A + 2B → B2 + A,proceeds by the following mechanism: (A is a catalyst.) A + B → AB (slow) AB + B → B2 + A (fast) What is the rate law expression for this reaction?

Consider the following proposed mechanism.If this mechanism for the overall reaction were correct,and if k1 were much less than k2,then the observed rate law would be 2A C + I I + B C + D

Calculate the activation energy,Ea,for N2O5(g) → 2 NO2(g) + 1/2 O2(g) Given k (at 45.0 °C) = 5.79 × 10-4 s-1 and k (at 60.0 °C) = 3.83 × 10-3 s-1.(R = 8.314 J/K⋅mol)

The rate constant for a first-order reaction is 1.7 × 10-2 s-1 at 676 K and 3.9 × 10-2 s-1 at 880 K.Determine the activation energy of the reaction.(R = 8.314 J/K⋅mol)

Molecules must overcome a barrier called the activation energy if they are to react.The highest energy point reached during the progress of a reaction is called the ____.

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 is the effect of adding a catalyst to a reaction?

A suggested mechanism for the decomposition of ozone is as follows: O3 O2 + O fast equilibrium O + O3 2O2 slow step What is the rate law predicted by this mechanism?

For the formation of 1 mol of nitrosyl chloride at a given temperature,ΔrH = -37 kJ/mol. NO(g) + ½ Cl2(g) → NOCl(g) The activation energy for this reaction is 81 kJ/mol.What is the activation energy for the reverse reaction?

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

In a reaction coordinate diagram,reacting molecules are most unstable ______.

The rate constant at 366 K for a first-order reaction is 7.7 × 10-3 s-1 and the activation energy is 15.9 kJ/mol.What is the value of the frequency factor,A,in the Arrhenius equation? (R = 8.314 J/K⋅mol)

For the overall reaction A + 2B → C,which of the following mechanisms yields the correct overall chemical equation and is consistent with the rate equation below? Rate = k[A][B]

The reaction kinetics for a certain reaction are studied over several temperatures.Which of the following is/are not effected by a change in reaction temperature?

A catalyst ____.

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 rate constant for a reaction at 40.0°C is exactly 6 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.(R = 8.314 J/K⋅mol)

For the overall reaction 2A + B → C Which of the following mechanisms is/are consistent with a rate equation of rate = k[A]2[B]?

The reaction,A + 2B → B₂ + A,proceeds by the following mechanism: (A is a catalyst.) A + B → AB (slow) AB + B → B₂ + A (fast) What is the rate law expression for this reaction?

Consider the following proposed mechanism.If this mechanism for the overall reaction were correct,and if k₁ were much less than k₂,then the observed rate law would be 2A C + I I + B C + D

Calculate the activation energy,E_a,for N₂O₅(g) → 2 NO₂(g) + 1/2 O₂(g) Given k (at 45.0 °C) = 5.79 × 10^-4 s^-1 and k (at 60.0 °C) = 3.83 × 10^-3 s^-1.(R = 8.314 J/K⋅mol)

The rate constant for a first-order reaction is 1.7 × 10^-2 s^-1 at 676 K and 3.9 × 10^-2 s^-1 at 880 K.Determine the activation energy of the reaction.(R = 8.314 J/K⋅mol)

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?

A suggested mechanism for the decomposition of ozone is as follows: O₃ O₂ + O fast equilibrium O + O₃ 2O₂ slow step What is the rate law predicted by this mechanism?

For the formation of 1 mol of nitrosyl chloride at a given temperature,Δ_rH = -37 kJ/mol. NO(g) + ½ Cl₂(g) → NOCl(g) The activation energy for this reaction is 81 kJ/mol.What is the activation energy for the reverse reaction?

The rate constant at 366 K for a first-order reaction is 7.7 × 10^-3 s^-1 and the activation energy is 15.9 kJ/mol.What is the value of the frequency factor,A,in the Arrhenius equation? (R = 8.314 J/K⋅mol)

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?

For the overall reaction 2A + B → C Which of the following mechanisms is/are consistent with a rate equation of rate = k[A]²[B]?