Consider the reaction A + B → C + D. Is each of the following statements true or false? (c) If the reaction is an elementary reaction, the rate law of the reverse reaction is first order.

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insert step 1> Understand that an elementary reaction is a single-step process where the rate law can be directly written from the stoichiometry of the reaction.

insert step 2> For the given reaction A + B → C + D, if it is an elementary reaction, the rate law for the forward reaction is rate = k[A][B], where k is the rate constant.

insert step 3> Consider the reverse reaction C + D → A + B. If this reverse reaction is also elementary, its rate law can be written directly from its stoichiometry.

insert step 4> The rate law for the reverse reaction would be rate = k'[C][D], where k' is the rate constant for the reverse reaction.

insert step 5> Since the rate law for the reverse reaction depends on the concentration of two reactants, C and D, it is second order, not first order. Therefore, the statement is false.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Elementary Reactions

An elementary reaction is a single step process in which reactants are converted to products in a single transition state. The rate law for an elementary reaction can be directly derived from its stoichiometry, meaning the rate is proportional to the concentration of the reactants raised to the power of their coefficients in the balanced equation.

Rate Laws

Rate laws express the relationship between the rate of a chemical reaction and the concentration of its reactants. For elementary reactions, the rate law is straightforward, while for complex reactions, it may involve intermediates and cannot be directly inferred from stoichiometry. The order of the reaction indicates how the rate is affected by the concentration of reactants.

Reverse Reactions

The reverse reaction is the process in which products are converted back into reactants. For an elementary reaction, if the forward reaction is first order with respect to a reactant, the reverse reaction will also exhibit a specific order based on the stoichiometry of the products. Understanding the relationship between forward and reverse reactions is crucial for determining the rate laws of both directions.

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Textbook Question

The activation energy of an uncatalyzed reaction is 95 kJ/mol. The addition of a catalyst lowers the activation energy to 55 kJ/mol. Assuming that the collision factor remains the same, by what factor will the catalyst increase the rate of the reaction at (b) 125 °C?

Textbook Question

Consider the reaction A + B → C + D. Is each of the following statements true or false? (b) If the reaction is an elementary reaction, the rate law is second order.

Textbook Question

The reaction 2 NO(g) + O₂(g) → 2 NO₂ (g) is second order in NO and first order in O₂. When [NO] = 0.040 M, and [O₂] = 0.035 M, the observed rate of disappearance of NO is 9.3⨉10^-5 M/s. (b) What is the value of the rate constant?

Textbook Question

The reaction 2 NO(g) + O₂(g) → 2 NO₂ (g) is second order in NO and first order in O₂. When [NO] = 0.040 M, and [O₂] = 0.035 M, the observed rate of disappearance of NO is 9.3⨉10^-5 M/s. (c) What are the units of the rate constant?

Textbook Question

The reaction 2 NO(g) + O₂(g) → 2 NO₂ (g) is second order in NO and first order in O₂. When [NO] = 0.040 M, and [O₂] = 0.035 M, the observed rate of disappearance of NO is 9.3⨉10^-5 M/s. (d) What would happen to the rate if the concentration of NO were increased by a factor of 1.8?