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Determine the potential of the following...

Determine the potential of the following cell:
`Pt|H_2(g,0.1 "bar")|H^+(aq,10^(-3)M"||"MnO_4^-)(aq),0.1M)`
`Mn^(2+)(aq,0.01M),H^+(aq,0.01M)|Pt`
Given : `E_(MnO_4^(-)|Mn^(2+))^(@)=1.51V`

A

1.54V

B

1.48V

C

1.84V

D

none of these

Text Solution

AI Generated Solution

The correct Answer is:
To determine the potential of the given electrochemical cell, we will follow these steps: ### Step 1: Identify the Anode and Cathode Reactions The cell notation indicates that the left side is the anode and the right side is the cathode. **Anode Reaction:** At the anode, hydrogen gas is oxidized: \[ \text{H}_2(g) \rightarrow 2\text{H}^+(aq) + 2e^- \] The standard electrode potential for this reaction is \( E^\circ_{\text{anode}} = 0 \, \text{V} \). **Cathode Reaction:** At the cathode, the reduction of permanganate ion occurs: \[ \text{MnO}_4^-(aq) + 8\text{H}^+(aq) + 5e^- \rightarrow \text{Mn}^{2+}(aq) + 4\text{H}_2O(l) \] The standard electrode potential for this reaction is given as \( E^\circ_{\text{cathode}} = 1.51 \, \text{V} \). ### Step 2: Write the Overall Cell Reaction To balance the number of electrons transferred, we multiply the anode reaction by 5: \[ 5\text{H}_2(g) \rightarrow 10\text{H}^+(aq) + 10e^- \] Now, we can combine the anode and cathode reactions: \[ 2\text{MnO}_4^-(aq) + 10\text{H}^+(aq) + 5\text{H}_2(g) \rightarrow 2\text{Mn}^{2+}(aq) + 8\text{H}_2O(l) + 10\text{H}^+(aq) \] After canceling out the \(10\text{H}^+\) ions, the overall reaction simplifies to: \[ 2\text{MnO}_4^-(aq) + 5\text{H}_2(g) \rightarrow 2\text{Mn}^{2+}(aq) + 8\text{H}_2O(l) + 6\text{H}^+(aq) \] ### Step 3: Calculate the Standard Cell Potential The standard cell potential (\(E^\circ_{\text{cell}}\)) is calculated using: \[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \] Substituting the values: \[ E^\circ_{\text{cell}} = 1.51 \, \text{V} - 0 \, \text{V} = 1.51 \, \text{V} \] ### Step 4: Apply the Nernst Equation The Nernst equation is given by: \[ E_{\text{cell}} = E^\circ_{\text{cell}} - \frac{0.0591}{n} \log Q \] Where \(n\) is the number of moles of electrons transferred (which is 10) and \(Q\) is the reaction quotient. **Calculate Q:** The reaction quotient \(Q\) is given by: \[ Q = \frac{[\text{Mn}^{2+}]^2 \cdot [\text{H}^+]^6}{[\text{MnO}_4^-]^2 \cdot P_{\text{H}_2}^5} \] Substituting the concentrations: - \([\text{Mn}^{2+}] = 0.01 \, \text{M}\) - \([\text{H}^+] = 10^{-3} \, \text{M}\) - \([\text{MnO}_4^-] = 0.1 \, \text{M}\) - \(P_{\text{H}_2} = 0.1 \, \text{bar}\) Thus, \[ Q = \frac{(0.01)^2 \cdot (10^{-3})^6}{(0.1)^2 \cdot (0.1)^5} \] Calculating \(Q\): \[ Q = \frac{(10^{-4}) \cdot (10^{-18})}{(10^{-2}) \cdot (10^{-5})} = \frac{10^{-22}}{10^{-7}} = 10^{-15} \] ### Step 5: Substitute into the Nernst Equation Now substituting into the Nernst equation: \[ E_{\text{cell}} = 1.51 \, \text{V} - \frac{0.0591}{10} \log(10^{-15}) \] Calculating the log term: \[ \log(10^{-15}) = -15 \] Thus, \[ E_{\text{cell}} = 1.51 \, \text{V} - \frac{0.0591}{10} \cdot (-15) \] \[ E_{\text{cell}} = 1.51 \, \text{V} + 0.885 \, \text{V} \] \[ E_{\text{cell}} \approx 1.48 \, \text{V} \] ### Final Answer The potential of the cell is approximately: \[ \boxed{1.48 \, \text{V}} \]
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