Problem 18
Question
Write a general rate law for the reaction $$\mathrm{H}_{2} \mathrm{O}_{2}(a q)+3 \mathrm{I}^{-}(a q)+2 \mathrm{H}^{+}(a q) \rightarrow \mathrm{I}_{3}^{-}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)$$ using \(x, y, z\) as orders.
Step-by-Step Solution
Verified Answer
The general rate law for the given reaction is:
\[Rate = k[H_2O_2]^x[I^-]^y[H^+]^z \]
1Step 1: Identify reactants
In the given reaction, we have three reactants: Hydrogen peroxide (\(H_2O_2\)), iodide ion (\(I^-\)), and hydrogen ion (\(H^+\)). The products of this reaction are Triiodide ion (\(I_3^-\)) and water (\(H_2O\)).
Step 2: Write the rate law with variables x, y, and z as orders
2Step 2: Write general rate law
The general rate law of a reaction is given by the equation:
\[Rate = k[Reactant_1]^x[Reactant_2]^y[Reactant_3]^z \]
where k is the rate constant, and x, y, and z are the orders of the reaction with respect to the respective reactants. In our case:
Rate = \[k[H_2O_2]^x[I^-]^y[H^+]^z \]
Step 3: Final rate law
3Step 3: Final rate law
The general rate law for the given reaction is:
\[Rate = k[H_2O_2]^x[I^-]^y[H^+]^z \]
Key Concepts
Reaction KineticsRate ConstantOrder of Reaction
Reaction Kinetics
Understanding reaction kinetics is pivotal in studying how chemical reactions occur and develop over time. It involves measuring the rate of a chemical reaction and determining the sequence of steps, known as the reaction mechanism, through which reactants transform into products.
For the provided exercise, which explores the reaction of hydrogen peroxide with iodide ions and hydrogen ions, reaction kinetics helps us to understand how these substances react together. More specifically, we are interested in how the concentration of each reactant influences the rate of reaction.
In practical settings, we observe this by monitoring concentrations of reactants over time and describing these changes mathematically. This hands-on approach yields valuable insights into the system's behavior, guides predictions, and informs the development of new products and processes in industries such as pharmaceuticals, materials science, and environmental engineering.
For the provided exercise, which explores the reaction of hydrogen peroxide with iodide ions and hydrogen ions, reaction kinetics helps us to understand how these substances react together. More specifically, we are interested in how the concentration of each reactant influences the rate of reaction.
In practical settings, we observe this by monitoring concentrations of reactants over time and describing these changes mathematically. This hands-on approach yields valuable insights into the system's behavior, guides predictions, and informs the development of new products and processes in industries such as pharmaceuticals, materials science, and environmental engineering.
Rate Constant
The rate constant in reaction kinetics, designated as 'k,' is a proportionality factor that connects the concentrations of reactants to the rate of the reaction. It is specific to each chemical reaction and varies with temperature. In our exercise, the rate constant helps us quantify the speed of the reaction.
We can conceptualize the rate constant as the reaction's 'pace setter.' A larger rate constant indicates a faster reaction under the same conditions, which is significant in industrial processes that rely on efficient chemical synthesis.
Since the rate constant can be sensitive to environmental changes, it becomes a critical parameter to control in both laboratory experimentation and industrial chemical production. An example of practical importance would be in the pharmaceutical industry, where the rate constant must be carefully managed to ensure the quality and safety of drug manufacturing.
We can conceptualize the rate constant as the reaction's 'pace setter.' A larger rate constant indicates a faster reaction under the same conditions, which is significant in industrial processes that rely on efficient chemical synthesis.
Since the rate constant can be sensitive to environmental changes, it becomes a critical parameter to control in both laboratory experimentation and industrial chemical production. An example of practical importance would be in the pharmaceutical industry, where the rate constant must be carefully managed to ensure the quality and safety of drug manufacturing.
Order of Reaction
The order of reaction provides insight into the relationship between the concentration of reactants and the rate of the chemical reaction. It is defined by the exponents 'x,' 'y,' and 'z' in our rate law expression, where these exponents represent how the rate is affected by changes in reactant concentrations.
An order of one implies a directly proportional relationship; as reactant concentration doubles, so does the reaction rate. An order of zero means the concentration has no effect on the rate, while fractional or negative orders indicate more complex relationships.
Determining the order of reaction can assist in unraveling the reaction mechanism and is fundamental in the design and analysis of chemical processes. As such, chemists and engineers use this information to optimize conditions to achieve desirable reaction speeds and yields, which is tantamount in processes ranging from the synthesis of fine chemicals to the treatment of waste products.
An order of one implies a directly proportional relationship; as reactant concentration doubles, so does the reaction rate. An order of zero means the concentration has no effect on the rate, while fractional or negative orders indicate more complex relationships.
Determining the order of reaction can assist in unraveling the reaction mechanism and is fundamental in the design and analysis of chemical processes. As such, chemists and engineers use this information to optimize conditions to achieve desirable reaction speeds and yields, which is tantamount in processes ranging from the synthesis of fine chemicals to the treatment of waste products.
Other exercises in this chapter
Problem 14
Consider our substitution reaction between \(\mathrm{OH}^{-}\) and \(\mathrm{CH}_{3} \mathrm{Br}\). Imagine it is occurring in a solution where there are 1000 c
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Write a general rate law for the reaction $$2 \mathrm{NO}+\mathrm{O}_{2} \rightarrow 2 \mathrm{NO}_{2}$$ using \(x\) and \(y\) as orders.
View solution Problem 20
Why should the number of collisions per second between reactant molecules have anything to do with their concentration?
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For the reaction $$\mathrm{BrO}_{3}^{-}+5 \mathrm{Br}^{-}+6 \mathrm{H}^{+} \rightarrow 3 \mathrm{Br}_{2}+3 \mathrm{H}_{2} \mathrm{O}$$ the experimentally determ
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