In a hydrocarbon solution, the gold compound (CH 3 ) 3 AuPH 3 decomposes into ethane (C 2 H 6 ) and a different gold compound, (CH 3 )AuPH 3 . The following mechanism has been proposed for the decomposition of (CH 3 ) 3 AuPH 3 : Step 1: (CH 3 ) 3 AuPH 3 k 1 ⇌k -1 (CH 3 ) 3 Au + PH 3 (fast) Step 2: (CH 3 ) 3 Au k 2 → C 2 H 6 + (CH 3 )Au (slow) Step 3: (CH 3 )Au + PH 3 k 3 → (CH 3 )AuPH 3 (fast) (f) What would be the effect on the reaction rate of adding PH 3 to the solution of (CH 3 ) 3 AuPH 3 ?

Hi everyone for this problem. It reads hydrogen peroxide decomposes quickly into water and oxygen gas in the presence of a platinum catalyst. The decomposition reaction takes place in two steps. Will the rate of the reaction change if oxygen is removed from the reaction mixture? So we want to answer the question of Will the rate of the reaction change? Okay, so the given reaction is a two step reaction with one slow step and one fast step. The rate of reaction depends only on the rate of the slow reaction. This is why the slow step is known as the rate limiting step. Okay, so this is our rate limiting. So the first step of the reaction is a slow step and the second one is the fast step. Oxygen is a component or product of the fast step. Okay, as we can see here, any change we make to the fast step will not affect the overall rate of the reaction. Therefore changing the concentration of oxygen will have no effect on the rate of the reaction. So the reaction is going to remain the same. Okay, so this is the answer to this question. The rate of the reaction will remain the same. That's the end of this problem. And that's the answer to this problem. I hope this was helpful

Ch.14 - Chemical Kinetics

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Brown 14th Edition

Ch.14 - Chemical Kinetics

Problem 112f

Chapter 14, Problem 112f

In a hydrocarbon solution, the gold compound (CH₃)₃AuPH₃ decomposes into ethane (C₂H₆) and a different gold compound, (CH₃)AuPH₃. The following mechanism has been proposed for the decomposition of (CH₃)₃AuPH₃:
Step 1: (CH₃)₃AuPH₃ k₁⇌k_-1 (CH₃)₃Au + PH₃ (fast)
Step 2: (CH₃)₃Au k₂→ C₂H₆ + (CH₃)Au (slow)
Step 3: (CH₃)Au + PH₃ k₃→ (CH₃)AuPH₃ (fast)
(f) What would be the effect on the reaction rate of adding PH₃ to the solution of (CH₃)₃AuPH₃?

Verified step by step guidance

Identify the rate-determining step in the mechanism, which is the slowest step. In this case, it is Step 2: (CH_3)_3Au -> C_2H_6 + (CH_3)Au.

Recognize that the rate of the overall reaction is determined by the rate of the slowest step, Step 2.

Consider the role of PH_3 in the mechanism. PH_3 is involved in Step 1 and Step 3, both of which are fast steps.

Understand that since PH_3 is not involved in the rate-determining step (Step 2), adding more PH_3 will not affect the rate of the slow step.

Conclude that adding PH_3 to the solution will not change the overall reaction rate, as it does not influence the rate-determining step.

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Key Concepts

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

Reaction Mechanism

A reaction mechanism describes the step-by-step sequence of elementary reactions by which overall chemical change occurs. Understanding the individual steps, including their rates and intermediates, is crucial for predicting how changes in conditions, such as concentration, will affect the overall reaction rate.

Rate Law

The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. It is determined by the slowest step in the reaction mechanism, which dictates how the reaction rate changes with varying concentrations of reactants, such as the effect of adding PH3 in this case.

Catalysis and Inhibition

Catalysis involves the acceleration of a chemical reaction by a substance (catalyst) that is not consumed in the reaction. Conversely, the addition of certain substances can inhibit the reaction rate. Understanding how PH3 interacts with the reactants can clarify whether it acts as a catalyst or an inhibitor in the decomposition of (CH3)3AuPH3.

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Related Practice

Textbook Question

In a hydrocarbon solution, the gold compound (CH₃)₃AuPH₃ decomposes into ethane (C₂H₆) and a different gold compound, (CH₃)AuPH₃. The following mechanism has been proposed for the decomposition of (CH₃)₃AuPH₃:

Step 1: (CH₃)₃AuPH₃ k₁⇌k_-1 (CH₃)₃Au + PH₃ (fast)

Step 2: (CH₃)₃Au k₂→ C₂H₆ + (CH₃)Au (slow)

Step 3: (CH₃)Au + PH₃ k₃→ (CH₃)AuPH₃ (fast)

(a) What is the overall reaction?

(b) What are the intermediates in the mechanism?

Textbook Question

Step 1: (CH₃)₃AuPH₃ k₁⇌k_-1 (CH₃)₃Au + PH₃ (fast)

Step 2: (CH₃)₃Au k₂→ C₂H₆ + (CH₃)Au (slow)

Step 3: (CH₃)Au + PH₃ k₃→ (CH₃)AuPH₃ (fast)

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Textbook Question

Step 1: (CH₃)₃AuPH₃ k₁⇌k_-1 (CH₃)₃Au + PH₃ (fast)

Step 2: (CH₃)₃Au k₂→ C₂H₆ + (CH₃)Au (slow)

Step 3: (CH₃)Au + PH₃ k₃→ (CH₃)AuPH₃ (fast)

(e) What is the rate law predicted by this mechanism?

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Textbook Question

Platinum nanoparticles of diameter 2 nm are important catalysts in carbon monoxide oxidation to carbon dioxide. Platinum crystallizes in a face-centered cubic arrangement with an edge length of 3.924 Å. (b) Estimate how many platinum atoms are on the surface of a 2.0-nm Pt sphere, using the surface area of a sphere (4πr²) and assuming that the 'footprint' of one Pt atom can be estimated from its atomic diameter of 2.8 A .

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Textbook Question

Platinum nanoparticles of diameter 2 nm are important catalysts in carbon monoxide oxidation to carbon dioxide. Platinum crystallizes in a face-centered cubic arrangement with an edge length of 3.924 Å. (c) Using your results from (a) and (b), calculate the percentage of Pt atoms that are on the surface of a 2.0-nm nanoparticle. (d) Repeat these calculations for a 5.0-nm platinum nanoparticle.

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Textbook Question

One of the many remarkable enzymes in the human body is carbonic anhydrase, which catalyzes the interconversion of carbon dioxide and water with bicarbonate ion and protons. If it were not for this enzyme, the body could not rid itself rapidly enough of the CO2 accumulated by cell metabolism. The enzyme catalyzes the dehydration (release to air) of up to 107 CO2 molecules per second. Which components of this description correspond to the terms enzyme, substrate, and turnover number?

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