Calculating the Remaining Concentration of R

Oct 13, 2025 by wbrum.org 4 views

Understanding the First-Order Reaction and Calculating the Remaining Concentration of R

Introduction to First-Order Reactions

In chemistry, a first-order reaction is a type of chemical reaction where the rate of reaction is directly proportional to the concentration of one reactant. The general equation for a first-order reaction is:

A \rightarrow B

where $A$ is the reactant and $B$ is the product. The rate of reaction is given by the equation:

\frac{d[A]}{dt} = -k[A]

where $k$ is the rate constant and $[A]$ is the concentration of the reactant.

Given Data and Reaction

In this problem, we are given the reaction:

R \rightarrow P

and the initial concentration of $R$ is 10 M. The rate constant $k$ is given as $2 \times 10^{-3}$ min $^{-1}$ . We are asked to find the percentage of $R$ that remains after the reaction proceeds for 10 minutes.

Calculating the Remaining Concentration of R

To calculate the remaining concentration of $R$ , we can use the integrated rate law for a first-order reaction:

\ln\left(\frac{[A]_t}{[A]_0}\right) = -kt

where $[A]_t$ is the concentration of the reactant at time $t$ , $[A]_0$ is the initial concentration of the reactant, and $k$ is the rate constant.

Substituting the Given Values

We can substitute the given values into the equation:

\ln\left(\frac{[R]_t}{10}\right) = -2 \times 10^{-3} \times 10

Simplifying the Equation

Simplifying the equation, we get:

\ln\left(\frac{[R]_t}{10}\right) = -0.02

Taking the Natural Logarithm

Taking the natural logarithm of both sides, we get:

\frac{[R]_t}{10} = e^{-0.02}

Evaluating the Exponential Function

Evaluating the exponential function, we get:

\frac{[R]_t}{10} = 0.9802

Solving for [R]t

Solving for $[R]_t$ , we get:

[R]_t = 9.802 \text{ M}

Calculating the Percentage of R Remaining

To calculate the percentage of $R$ remaining, we can divide the remaining concentration by the initial concentration and multiply by 100:

\text{Percentage of R remaining} = \frac{[R]_t}{[R]_0} \times 100

Substituting the Values

Substituting the values, we get:

\text{Percentage of R remaining} = \frac{9.802}{10} \times 100

Calculating the Percentage

Calculating the percentage, we get:

\text{Percentage of R remaining} = 98.02\%

Conclusion

In this problem, we used the integrated rate law for a first-order reaction to calculate the remaining concentration of $R$ after the reaction proceeds for 10 minutes. We found that 98.02% of $R$ remains after the reaction proceeds for 10 minutes.

References

Atkins, P. W. (2010). Physical Chemistry. Oxford University Press.
Levine, I. N. (2012). Physical Chemistry. McGraw-Hill.

Further Reading

For more information on first-order reactions, see the following resources:

Atkins, P. W. (2010). Physical Chemistry. Oxford University Press.
Levine, I. N. (2012). Physical Chemistry. McGraw-Hill.

For more information on the integrated rate law, see the following resources:

Atkins, P. W. (2010). Physical Chemistry. Oxford University Press.
Levine, I. N. (2012). Physical Chemistry. McGraw-Hill.
Q&A: First-Order Reactions and Calculating the Remaining Concentration of R

Q: What is a first-order reaction?

A: A first-order reaction is a type of chemical reaction where the rate of reaction is directly proportional to the concentration of one reactant. The general equation for a first-order reaction is:

A \rightarrow B

where $A$ is the reactant and $B$ is the product.

Q: What is the integrated rate law for a first-order reaction?

A: The integrated rate law for a first-order reaction is:

\ln\left(\frac{[A]_t}{[A]_0}\right) = -kt

where $[A]_t$ is the concentration of the reactant at time $t$ , $[A]_0$ is the initial concentration of the reactant, and $k$ is the rate constant.

Q: How do I calculate the remaining concentration of R after the reaction proceeds for 10 minutes?

A: To calculate the remaining concentration of R, you can use the integrated rate law for a first-order reaction:

\ln\left(\frac{[R]_t}{10}\right) = -2 \times 10^{-3} \times 10

Simplifying the equation, we get:

\ln\left(\frac{[R]_t}{10}\right) = -0.02

Taking the natural logarithm of both sides, we get:

\frac{[R]_t}{10} = e^{-0.02}

Evaluating the exponential function, we get:

\frac{[R]_t}{10} = 0.9802

Solving for $[R]_t$ , we get:

[R]_t = 9.802 \text{ M}

Q: What percentage of R remains after the reaction proceeds for 10 minutes?

A: To calculate the percentage of R remaining, you can divide the remaining concentration by the initial concentration and multiply by 100:

\text{Percentage of R remaining} = \frac{[R]_t}{[R]_0} \times 100

Substituting the values, we get:

\text{Percentage of R remaining} = \frac{9.802}{10} \times 100

Calculating the percentage, we get:

\text{Percentage of R remaining} = 98.02\%

Q: What are some common mistakes to avoid when calculating the remaining concentration of R?

A: Some common mistakes to avoid when calculating the remaining concentration of R include:

Not using the correct integrated rate law for a first-order reaction
Not substituting the correct values into the equation
Not simplifying the equation correctly
Not taking the natural logarithm of both sides
Not evaluating the exponential function correctly

Q: What are some resources for further learning on first-order reactions and the integrated rate law?

A: Some resources for further learning on first-order reactions and the integrated rate law include:

Atkins, P. W. (2010). Physical Chemistry. Oxford University Press.
Levine, I. N. (2012). Physical Chemistry. McGraw-Hill.
Online tutorials and videos on first-order reactions and the integrated rate law.

Q: Can I use the integrated rate law to calculate the remaining concentration of R for any time period?

A: Yes, you can use the integrated rate law to calculate the remaining concentration of R for any time period. Simply substitute the correct values into the equation and solve for $[R]_t$ .

Q: What is the significance of the rate constant k in the integrated rate law?

A: The rate constant k is a measure of the rate at which the reaction occurs. A larger value of k indicates a faster reaction rate, while a smaller value of k indicates a slower reaction rate.