The rate constant for this first-order reaction is 0.0700 s- at 400 °C. A products > After how many seconds will 16.2% of the reactant remain? t =

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**First-Order Reaction Kinetics**

In this exercise, we are given a first-order chemical reaction where reactant A is converted into products. The rate constant (k) for this first-order reaction is 0.0700 s⁻¹ at 400 °C.

\[ A \longrightarrow \text{products} \]

We are asked to determine the time (t) after which only 16.2% of the reactant remains.

To find the time t, we can use the integrated rate law for a first-order reaction, which is given by:

\[ [A]_t = [A]_0 e^{-kt} \]

Where:
- \([A]_t\) is the concentration of reactant A at time t
- \([A]_0\) is the initial concentration of reactant A
- \(k\) is the first-order rate constant
- \(t\) is the time

Given that we know what percentage of the reactant remains, we can rearrange the equation as:

\[ \frac{[A]_t}{[A]_0} = e^{-kt} \]

By substituting \(\frac{[A]_t}{[A]_0} = 0.162\):

\[ 0.162 = e^{-kt} \]

Taking the natural logarithm (ln) of both sides:

\[ \ln(0.162) = -kt \]

We then solve for t:

\[ t = \frac{\ln(0.162)}{-k} \]

Finally, by plugging in the given rate constant \( k = 0.0700 \, \text{s}^{-1} \):

\[ t = \frac{\ln(0.162)}{-0.0700\, \text{s}^{-1}} \]

\[
t = \boxed{\ \ \ \ \ \ \ }
\]

This calculated value represents the time in seconds at which 16.2% of the original amount of reactant A remains.
Transcribed Image Text:**First-Order Reaction Kinetics** In this exercise, we are given a first-order chemical reaction where reactant A is converted into products. The rate constant (k) for this first-order reaction is 0.0700 s⁻¹ at 400 °C. \[ A \longrightarrow \text{products} \] We are asked to determine the time (t) after which only 16.2% of the reactant remains. To find the time t, we can use the integrated rate law for a first-order reaction, which is given by: \[ [A]_t = [A]_0 e^{-kt} \] Where: - \([A]_t\) is the concentration of reactant A at time t - \([A]_0\) is the initial concentration of reactant A - \(k\) is the first-order rate constant - \(t\) is the time Given that we know what percentage of the reactant remains, we can rearrange the equation as: \[ \frac{[A]_t}{[A]_0} = e^{-kt} \] By substituting \(\frac{[A]_t}{[A]_0} = 0.162\): \[ 0.162 = e^{-kt} \] Taking the natural logarithm (ln) of both sides: \[ \ln(0.162) = -kt \] We then solve for t: \[ t = \frac{\ln(0.162)}{-k} \] Finally, by plugging in the given rate constant \( k = 0.0700 \, \text{s}^{-1} \): \[ t = \frac{\ln(0.162)}{-0.0700\, \text{s}^{-1}} \] \[ t = \boxed{\ \ \ \ \ \ \ } \] This calculated value represents the time in seconds at which 16.2% of the original amount of reactant A remains.
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