题目

某HCl溶液中 c_({Fe)^3+} = c_({Fe)^2+} = 1 , (mol) cdot (L)^-1，此时溶液中铁电对的条件电位 E_({Fe)^3+/(Fe)^2+}^theta' 为（）A. E_({Fe)^3+/(Fe)^2+}^theta' = E_({Fe)^3+/(Fe)^2+}^theta + 0.059 lg (I_({Fe)^3+})/(I_({Fe)^2+)} (I为离子强度)B. E_({Fe)^3+/(Fe)^2+}^theta' = E_({Fe)^3+/(Fe)^2+}^theta + 0.059 lg (gamma_({Fe)^3+} alpha_({Fe)^2+})/(gamma_({Fe)^2+) alpha_({Fe)^3+}}C. E_({Fe)^3+/(Fe)^2+}^theta' = E_({Fe)^3+/(Fe)^2+}^thetaD. E_({Fe)^3+/(Fe)^2+}^theta' = E_({Fe)^3+/(Fe)^2+}^theta + 0.059 lg (alpha_({Fe)^2+})/(alpha_({Fe)^3+)}

某HCl溶液中 $c_{\text{Fe}^{3+}} = c_{\text{Fe}^{2+}} = 1 \, \text{mol} \cdot \text{L}^{-1}$，此时溶液中铁电对的条件电位 $E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta'}$ 为（）

A. $E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta'} = E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta} + 0.059 \lg \frac{I_{\text{Fe}^{3+}}}{I_{\text{Fe}^{2+}}}$ (I为离子强度)

B. $E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta'} = E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta} + 0.059 \lg \frac{\gamma_{\text{Fe}^{3+}} \alpha_{\text{Fe}^{2+}}}{\gamma_{\text{Fe}^{2+}} \alpha_{\text{Fe}^{3+}}}$

C. $E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta'} = E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta}$

D. $E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta'} = E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\theta} + 0.059 \lg \frac{\alpha_{\text{Fe}^{2+}}}{\alpha_{\text{Fe}^{3+}}}$

题目解答

答案

根据条件电极电位公式： \[ E^{\theta'}_{Fe^{3+}/Fe^{2+}} = E^{\theta}_{Fe^{3+}/Fe^{2+}} + 0.059 \log \frac{a_{Fe^{3+}}}{a_{Fe^{2+}}} \] 在 HCl 溶液中，$ a_{Fe^{3+}} = \gamma_{Fe^{3+}} c_{Fe^{3+}} / \alpha_{Fe^{3+}} $，$ a_{Fe^{2+}} = \gamma_{Fe^{2+}} c_{Fe^{2+}} / \alpha_{Fe^{2+}} $。由于 $ c_{Fe^{3+}} = c_{Fe^{2+}} = 1 \, \text{mol·L}^{-1} $，可得： \[ E^{\theta'}_{Fe^{3+}/Fe^{2+}} = E^{\theta}_{Fe^{3+}/Fe^{2+}} + 0.059 \log \frac{\gamma_{Fe^{3+}} \alpha_{Fe^{2+}}}{\gamma_{Fe^{2+}} \alpha_{Fe^{3+}}} \] 选项A未考虑 $ \alpha $，C未考虑 $ \gamma $ 和 $ \alpha $，D未考虑 $ \gamma $，均不正确。答案：B. $ E^{\theta'}_{Fe^{3+}/Fe^{2+}} = E^{\theta}_{Fe^{3+}/Fe^{2+}} + 0.059 \log \frac{\gamma_{Fe^{3+}} \alpha_{Fe^{2+}}}{\gamma_{Fe^{2+}} \alpha_{Fe^{3+}}} $