Conductivity Kinetics
1. **Problem statement:** We are given the conductivity $\sigma$ of a reaction mixture over time $t$ during the hydrolysis of 2-chlorobutane ($\mathrm{C_4H_9Cl}$) to 2-butanol ($\mathrm{C_4H_9OH}$). The goal is to analyze the kinetics of the reaction using the conductivity data.
2. **Given data:**
- Initial volume $V_0 = 50$ mL
- Volume $V_1 = 25$ mL
- Volume $V_2 = 1$ mL
- Temperature $20^\circ$C
- Molar mass $M(\mathrm{C_4H_9Cl}) = 92.57$ g/mol
- Density of water $\rho(\mathrm{H_2O}) = 1$ g/cm$^3$
- Distance between electrodes $d = 0.84$ m
- Conductivity $\sigma$ (S/m) at times $t$ (s) given in the table
3. **Understanding the reaction:**
$$\mathrm{C_4H_9Cl + 2H_2O \rightarrow C_4H_9OH + Cl^- + H_3O^+}$$
The conductivity increases as ions $\mathrm{Cl^-}$ and $\mathrm{H_3O^+}$ are produced.
4. **Calculate the maximum conductivity $\sigma_\infty$:**
From the data, conductivity plateaus at $\sigma_\infty = 1.955$ S/m after 1800 s.
5. **Calculate the degree of reaction progress $\alpha(t)$:**
$$\alpha(t) = \frac{\sigma(t)}{\sigma_\infty}$$
This represents the fraction of reaction completed at time $t$.
6. **Calculate $\alpha(t)$ for each time point:**
For example, at $t=200$ s:
$$\alpha(200) = \frac{0.489}{1.955} \approx 0.250\quad (25\%)$$
Similarly for other times.
7. **Determine the reaction kinetics:**
Assuming a first-order reaction, the concentration of $\mathrm{C_4H_9Cl}$ decreases as:
$$[\mathrm{C_4H_9Cl}] = [\mathrm{C_4H_9Cl}]_0 (1 - \alpha(t))$$
The rate law is:
$$\ln\left(\frac{[\mathrm{C_4H_9Cl}]_0}{[\mathrm{C_4H_9Cl}]_0 (1 - \alpha(t))}\right) = kt$$
which simplifies to:
$$-\ln(1 - \alpha(t)) = kt$$
8. **Plot or calculate $-\ln(1 - \alpha(t))$ vs $t$ to find rate constant $k$:**
Using the data, calculate $-\ln(1 - \alpha(t))$ for each $t$ and perform linear regression to find slope $k$.
9. **Summary:**
- The reaction progress is monitored by conductivity.
- The degree of reaction $\alpha(t)$ is the ratio of conductivity at time $t$ to maximum conductivity.
- The reaction follows first-order kinetics with rate constant $k$ obtained from the slope of $-\ln(1 - \alpha(t))$ vs $t$.
**Final answer:** The reaction is first-order with respect to $\mathrm{C_4H_9Cl}$, and the rate constant $k$ can be determined from the conductivity data using:
$$k = \frac{-\ln(1 - \alpha(t))}{t}$$
where
$$\alpha(t) = \frac{\sigma(t)}{1.955}$$