/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 17 A chemical \(A\) is formed by an... [FREE SOLUTION] | 91Ó°ÊÓ

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A chemical \(A\) is formed by an irreversible reaction from chemicals \(B\) and \(C\). Assuming that the amounts of \(B\) and \(C\) are adequate to sustain the reaction, the amount of \(A\) formed at time \(t\) is governed by the differential equation, $$ \frac{\mathrm{d} A}{\mathrm{~d} t}=K(1-\alpha A)^{7} $$ If no \(A\) is present at time \(t=0\), find an expression for the amount of \(A\) present at time \(t\).

Short Answer

Expert verified
\( A(t) = \frac{1}{\alpha}\left(1 - \frac{1}{(1 + 6K\alpha t)^{1/6}}\right) \)

Step by step solution

01

Set Up the Differential Equation

We are given the differential equation \( \frac{\mathrm{d} A}{\mathrm{~d} t}=K(1-\alpha A)^{7} \), which describes the rate of change of substance \( A \). Our goal is to find \( A(t) \), the amount of \( A \) present at time \( t \).
02

Separate Variables for Integration

To solve the differential equation, we need to separate variables. Rewrite the equation as \( \frac{\mathrm{d} A}{(1-\alpha A)^{7}} = K \mathrm{d} t \). This allows us to integrate both sides separately.
03

Integrate Both Sides

Now, we need to integrate both sides. The left side integrates as \( \int \frac{\mathrm{d} A}{(1-\alpha A)^{7}} \), and the right side integrates as \( \int K \mathrm{d} t = Kt + C \), where \( C \) is the integration constant.
04

Solve the Integral

The integral of the left side, \( \int \frac{\mathrm{d} A}{(1-\alpha A)^{7}} \), is challenging. Using substitution and integration techniques, this results in \(-\frac{1}{6\alpha(1-\alpha A)^6}\).
05

Apply Initial Condition

We know that at \( t = 0 \), \( A = 0 \). Substitute these values into the equation to find the constant \( C \): \(-\frac{1}{6\alpha} = C\).
06

Solve for \( A(t) \)

Now substitute \( C \) back into the equation and solve for \( A(t) \): \(-\frac{1}{6\alpha(1-\alpha A)^6} = Kt - \frac{1}{6\alpha}\). Rearrange and solve for \( A(t) \). This will give you the expression for \( A \) in terms of \( t \).
07

Rearrange to Solve for \( A(t) \)

After simplification, you find that \( A(t) = \frac{1}{\alpha}\left(1 - \frac{1}{(1 + 6K\alpha t)^{1/6}}\right) \). This is the solution for the amount of \( A \) at any time \( t \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Integral Calculus
Integral calculus is a major branch of mathematics that is used to calculate areas, volumes, and many other concepts. It deals primarily with the concept of integration or the reverse process of differentiation. In this exercise, integration is key to solving the given differential equation. By integrating, we can find an expression that describes how the amount of a chemical substance, in this case, A, changes over time.
To find the amount of chemical A at time t, we initially rewrite the differential equation to allow separate integrations. The equation given is \( \frac{\mathrm{d} A}{(1-\alpha A)^{7}} = K \mathrm{d} t \). Here, the left side involves integrating a complex power of a binomial, while the right side is a straightforward linear integration with respect to time. The integral of \( K \mathrm{d} t \) gives \( Kt + C \) where \( C \) is a constant of integration. Solving the left side for \( A \) is more complex and involves substitution techniques. This yields a solution that is linked to understanding the kinetic rate of the reaction.
Chemical Reaction Kinetics
Chemical reaction kinetics explores the rates at which chemical processes occur and the factors that influence them. In this example, the formation of a substance, A, from chemicals B and C, depends on the concentration of A. The differential equation describes how A is formed over time, governed by a reaction that diminishes as more of A is present.
Here, the reaction kinetics are captured by the term \((1-\alpha A)^{7}\). This implies that the formation rate of A decreases as the product A accumulates, reflecting a characteristic rate law connected to the concentration of A. Understanding these kinetics is vital in predicting how reactions progress, especially in designing reactors or optimizing conditions for desired reaction pathways.
Variable Separation
Variable separation is a fundamental technique in solving differential equations, especially when different quantities change independently of each other. This method involves rearranging the differential equation so one side depends solely on one variable, allowing for independent integration of parts.
In the exercise, the original equation \( \frac{\mathrm{d} A}{\mathrm{d} t}=K(1-\alpha A)^{7} \) is rearranged as \( \frac{\mathrm{d} A}{(1-\alpha A)^{7}} = K \mathrm{d} t \). This separation allows for the variables, A and t, to be integrated separately. Such a technique not only simplifies the problem but also makes it feasible to compute an explicit solution for A in terms of t. The key to successful variable separation is ensuring that we fully isolate one variable on each side, in turn clarifying the structure needed for integration.

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Most popular questions from this chapter

Denote Euler's method solution of the initial-value problem $$ \frac{\mathrm{d} x}{\mathrm{~d} t}=\frac{x t}{t^{2}+2}, \quad x(1)=2 $$ using step size \(h=0.1\) by \(X_{\mathrm{a}}(t)\), and that using \(h=0.05\) by \(X_{\mathrm{b}}(t) .\) Find the values of \(X_{\mathrm{a}}(2)\) and \(X_{\mathrm{b}}(2) .\) Estimate the error in the value of \(X_{\mathrm{b}}(2)\), and suggest a value of step size that would provide a value of \(X(2)\) accurate to \(0.1 \%\). Find the value of \(X(2)\) using this step size. Find the exact solution of the initial-value problem, and determine the actual magnitude of the errors in \(X_{\mathrm{a}}(2), X_{\mathrm{b}}(2)\) and your final value of \(X(2)\)

Find the damping parameters and natural frequencies of the systems governed by the following second-order linear constant-coefficient differential equations: (a) \(\frac{\mathrm{d}^{2} x}{\mathrm{~d} t^{2}}+2 a \frac{\mathrm{d} x}{\mathrm{~d} t}+16 p^{2} x=0\) (b) \(2 \frac{\mathrm{d}^{2} x}{\mathrm{~d} t^{2}}+14 \frac{\mathrm{d} x}{\mathrm{~d} t}+\frac{1}{\alpha} x=0\) (c) \(2.41 \frac{\mathrm{d}^{2} x}{\mathrm{~d} t^{2}}+1.02 \frac{\mathrm{d} x}{\mathrm{~d} t}+7.63 x=0\) (d) \(\frac{1}{\eta} \frac{\mathrm{d}^{2} x}{\mathrm{~d} t^{2}}+40 \frac{\mathrm{d} x}{\mathrm{~d} t}+25 \eta x=0\) (e) \(1.88 \frac{\mathrm{d}^{2} x}{\mathrm{~d} t^{2}}+4.71 \frac{\mathrm{d} x}{\mathrm{~d} t}+0.48 x=0\)

Write a computer program to solve the initialvalue problem $$ \begin{aligned} &\frac{\mathrm{d}^{2} x}{\mathrm{~d} t^{2}}+x^{2} \frac{\mathrm{d} x}{\mathrm{~d} t}+x=\sin t \\ &x(0)=0, \quad \frac{\mathrm{d} x}{\mathrm{~d} t}(0)=1 \end{aligned} $$ using Euler's method. Use your program to find the value of \(X(0.4)\) using steps of \(h=0.01\) and \(h=0.005\). Hence estimate the accuracy of your value of \(X(0.4)\) and estimate the step size that would be necessary to obtain a value of \(X(0.4)\) accurate to \(4 \mathrm{dp}\).

Denote Euler's method solution of the initial-value problem $$ \frac{\mathrm{d} x}{\mathrm{~d} t}=\frac{1}{x t}, \quad x(1)=1 $$ using step size \(h=0.1\) by \(X_{\mathrm{a}}(t)\), and that using \(h=0.05\) by \(X_{\mathrm{b}}(t) .\) Find the values of \(X_{\mathrm{a}}(2)\) and \(X_{\mathrm{b}}(2)\). Estimate the error in the value of \(X_{\mathrm{b}}(2)\), and suggest a value of step size that would provide a value of \(X(2)\) accurate to \(0.2 \%\). Find the value of \(X(2)\) using this step size. Find the exact solution of the initial-value problem, and determine the actual magnitude of the errors in \(X_{\mathrm{a}}(2), X_{\mathrm{b}}(2)\) and your final value of \(X(2)\)

Find the solutions of the following initial-value problems: (a) \(\frac{\mathrm{d} x}{\mathrm{~d} t}=\frac{t^{2}+1}{x+2}, \quad x(0)=-2\) (b) \(t(t-1) \frac{\mathrm{d} x}{\mathrm{~d} t}=x(x+1), \quad x(2)=2\) (c) \(\frac{\mathrm{d} x}{\mathrm{~d} t}=\left(x^{2}-1\right) \cos t, \quad x(0)=2\) (d) \(\frac{\mathrm{d} x}{\mathrm{~d} t}=\mathrm{e}^{x+t}, \quad x(0)=a\) (e) \(\frac{\mathrm{d} x}{\mathrm{~d} t}=\frac{4 \ln t}{x^{2}}, \quad x(1)=0\)

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