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) (a) What is the overall reaction? (b) What are the intermediates in the mechanism?

Hello. In this problem, we are told the decomposition of hydrogen peroxide is catalyzed by platinum and involves the following steps were asked to determine then the reaction intermediate. So we can combine these two steps to find the overall reaction. The overall reaction then, if they appear on both the reactant and product side, they cancel. So we have platinum on the reacting side and platinum on the product side to those cancel. And then we have platinum combined with oxygen on the reactant and product side to those cancel. So then the overall reaction is two moles of hydrogen peroxide decomposing to form oxygen And two moles of water. So a intermediate is formed in one step and then consumed in a subsequent step and does not appear in the overall reaction. So if we look at what we marked off, don't appear in the overall reaction. And we see that the platinum bind with oxygen here is formed in this first step and then it is consumed in the second step. And it does not appear in our overall reaction. See then is our intermediate. Again, an intermediate is formed in one step and consumed in a subsequent step and does not appear in our overall reaction. And so in this case it is then the platinum that is combined with the oxygen. Thanks for watching. Hope this helps

Ch.14 - Chemical Kinetics

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Brown 14th Edition

Ch.14 - Chemical Kinetics

Problem 112a,b

Chapter 14, Problem 112a,b

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?

Verified step by step guidance

Step 1: To determine the overall reaction, we need to add up all the steps in the mechanism. Start by writing down each step of the mechanism: Step 1: (CH3)3AuPH3 ⇌ (CH3)3Au + PH3, Step 2: (CH3)3Au → C2H6 + (CH3)Au, Step 3: (CH3)Au + PH3 → (CH3)AuPH3.

Step 2: Cancel out any species that appear on both sides of the reaction steps. In this case, (CH3)3Au and PH3 are intermediates that appear in both the reactants and products of the steps.

Step 3: After canceling the intermediates, combine the remaining species to write the overall reaction. The reactants and products that are not canceled will form the overall balanced equation.

Step 4: Identify the intermediates in the mechanism. Intermediates are species that are produced in one step and consumed in another. In this mechanism, (CH3)3Au and (CH3)Au are intermediates.

Step 5: Summarize the findings: The overall reaction is the net result of the mechanism steps after canceling intermediates, and the intermediates are the species that do not appear in the overall reaction but are present in the mechanism steps.

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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 is a step-by-step description of the process by which reactants are converted into products. It outlines the individual steps, including the formation of intermediates and the transition states, which help in understanding how the overall reaction occurs. In this case, the mechanism involves multiple steps, with specific rates and intermediates that play crucial roles in the decomposition of the gold compound.

Intermediates

Intermediates are species that are formed during the reaction mechanism but are not present in the final products. They are typically unstable and exist only for a short duration. Identifying intermediates is essential for understanding the pathway of the reaction, as they can influence the rate and outcome of the overall reaction. In the provided mechanism, (CH3)Au and (CH3)AuPH3 are examples of intermediates.

Overall Reaction

The overall reaction represents the net change from reactants to products, summarizing the entire process in a single equation. It is derived by combining the individual steps of the mechanism and canceling out any intermediates that appear on both sides. For the given hydrocarbon solution, determining the overall reaction involves identifying the starting materials and the final products, which in this case are ethane and a different gold compound.

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Textbook Question

The following mechanism has been proposed for the gasphase reaction of chloroform 1CHCl32 and chlorine: Step 1: Cl21g2 Δ k1 k - 1 2 Cl1g2 1fast2 Step 2: Cl1g2 + CHCl31g2 ¡k2 HCl1g2 + CCl31g2 1slow2 Step 3: Cl1g2 + CCl31g2 ¡k3 CCl4 1fast2 (a) What is the overall reaction?

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Textbook Question

The following mechanism has been proposed for the gasphase reaction of chloroform 1CHCl32 and chlorine:

Step 1: Cl₂(g) k₁⇌ k_-1 2 Cl(g) (fast)

Step 2: Cl(g) + CHCl₃(g) k₂→ HCl(g) + CCl₃(g) (slow)

Step 3: Cl(g0 + CCl3(g) k₃→ CCl₄ (fast)

(e) What is the rate law predicted by this mechanism? (Hint: The overall reaction order is not an integer.)

Open Question

Consider the hypothetical reaction 2 A + B → 2 C + D. The following two-step mechanism is proposed for the reaction: Step 1: A + B → C + X Step 2: A + X → C + D. X is an unstable intermediate. (c) Your result for part (b) might be considered surprising for which of the following reasons: (i) The concentration of a product is in the rate law. (ii) There is a negative reaction order in the rate law. (iii) Both reasons (i) and (ii). (iv) Neither reasons (i) nor (ii).

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)

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Textbook Question