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Current Question (ID: 8637)

Question:

$\text{Consider the given data:}$ $\text{E}_{\text{Fe}^{3+}/\text{Fe}^{2+}} = 0.77; \text{E}_{\text{I}^-/\text{I}_2} = -0.54$ $\text{E}_{\text{Ag}^+/\text{Ag}} = 0.80; \text{E}_{\text{Cu}/\text{Cu}^{2+}} = -0.34$ $\text{E}_{\text{Fe}^{3+}/\text{Fe}^{2+}} = 0.77; \text{E}_{\text{Cu}/\text{Cu}^{2+}} = -0.34$ $\text{E}_{\text{Ag}/\text{Ag}^+} = -0.80; \text{E}_{\text{Fe}^{3+}/\text{Fe}^{2+}} = 0.77$ $\text{Using the electrode potential values given above, identify the reaction which is not feasible:}$

Options:

1. $\text{Fe}^{3+}_{(\text{aq})} \text{ and I}^-_{\text{aq})}$
2. $\text{Ag}^+_{(\text{aq})} \text{ and Cu}_{(\text{s})}$
3. $\text{Fe}^{3+}_{(\text{aq})} \text{ and Cu}_{(\text{s})}$
4. $\text{Ag}_{(\text{s})} \text{ and Fe}^{3+}_{(\text{aq})}$

Solution:

$\text{Hint: For feasible E}_{\text{cell}} \text{ must be positive}$ $\text{(a) The possible reaction between Fe}^{3+}_{(\text{aq})} + \text{I}^-_{(\text{aq})}$ $2\text{Fe}^{3+}_{(\text{aq})} + 2\text{I}^-_{(\text{aq})} \rightarrow 2\text{Fe}^{2+}_{(\text{aq})} + \text{I}_{2(\text{s})} \text{ is given by,}$ $\text{Oxidation half equation : } 2\text{I}^-_{(\text{aq})} \rightarrow \text{I}_{2(\text{s})} + 2\text{e}^- : \text{E}^\circ = -0.54\text{V}$ $\text{Reduction half equation : } [\text{Fe}^{3+}_{(\text{aq})} + \text{e}^- \rightarrow \text{Fe}^{2+}_{(\text{aq})}] \times 2;$ $\text{E}^\circ = +0.77\text{V} \quad 2\text{Fe}^{3+}_{(\text{aq})} + 2\text{I}^-_{(\text{aq})} \rightarrow 2\text{Fe}^{2+}_{(\text{aq})} + \text{I}_{2(\text{s})};$ $\text{E}^\circ = +0.23\text{V}$ $\text{E}^\circ \text{ for the overall reaction is positive. Thus, the reaction between Fe}^{3+}_{(\text{aq})} \text{ and I}^-_{(\text{aq})} \text{ is feasible.}$ $\text{(b) The possible reaction between Ag}^+_{(\text{aq})} + \text{Cu}_{(\text{s})} \text{ is given by,}$ $2\text{Ag}^+_{(\text{aq})} + \text{Cu}_{(\text{s})} \rightarrow 2\text{Ag}_{(\text{s})} + \text{Cu}^{2+}_{(\text{aq})}$ $\text{Oxidation half equation : Cu}_{(\text{s})} \rightarrow \text{Cu}^{2+}_{(\text{aq})} + 2\text{e}^- : \text{E}^\circ = -0.34\text{V}$ $\text{Reduction half equation : } [\text{Ag}^+_{(\text{aq})} + \text{e}^- \rightarrow \text{Ag}_{(\text{s})}] \times 2;$ $\text{E}^\circ = +0.80\text{V} \quad 2\text{Ag}^+_{(\text{aq})} + \text{Cu}_{(\text{s})} \rightarrow 2\text{Ag}_{(\text{s})} + \text{Cu}^{2+};$ $\text{E}^\circ = +0.46\text{V}$ $\text{E}^\circ \text{ positive for the overall reaction is positive. Hence, the reaction between Ag}^+_{(\text{aq})} \text{ and Cu}_{(\text{s})} \text{ is feasible.}$ $\text{(c) The possible reaction between Fe}^{3+}_{(\text{aq})} \text{ and Cu}_{(\text{s})} \text{ is given by,}$ $2\text{Fe}^{3+}_{(\text{aq})} + \text{Cu}_{(\text{s})} \rightarrow 2\text{Fe}^{2+}_{(\text{s})} + \text{Cu}^{2+}_{(\text{aq})}$ $\text{Oxidation half equation : Cu}_{(\text{s})} \rightarrow \text{Cu}^{2+}_{(\text{aq})} + 2\text{e}^- ; \text{E}^\circ = -0.34\text{V}$ $\text{Reduction half equation : } [\text{Fe}^{3+}_{(\text{aq})} + \text{e}^- \rightarrow \text{Fe}^{2+}_{(\text{s})}] \times 2;$ $\text{E}^\circ = +0.77\text{V} \quad 2\text{Fe}^{3+}_{(\text{aq})} + \text{Cu}_{(\text{s})} \rightarrow 2\text{Fe}^{2+}_{(\text{s})} + \text{Cu}^{2+}_{(\text{aq})};$ $\text{E}^\circ = +0.43\text{V}$ $\text{E}^\circ \text{ positive for the overall reaction is positive. Hence, the reaction between Fe}^{3+}_{(\text{aq})} \text{ and Cu}_{(\text{s})} \text{ is feasible.}$ $\text{(d) The possible reaction between Ag}_{(\text{s})} \text{ and Fe}^{3+}_{(\text{aq})}$ $\text{Ag}_{(\text{s})} + 2\text{Fe}^{3+}_{(\text{aq})} \rightarrow \text{Ag}^+_{(\text{aq})} + \text{Fe}^{2+}_{(\text{aq})} \text{ is given by,}$ $\text{Oxidation half equation : Ag}_{(\text{s})} \rightarrow \text{Ag}^+_{(\text{aq})} + \text{e}^- ; \text{E}^\circ = -0.80\text{V}$ $\text{Reduction half equation : Fe}^{3+}_{(\text{aq})} + \text{e}^- \rightarrow \text{Fe}^{2+}_{(\text{aq})} ; \text{E}^\circ = +0.77$ $\text{V Ag}_{(\text{s})} + \text{Fe}^{3+}_{(\text{aq})} \rightarrow \text{Ag}^+_{(\text{aq})} + \text{Fe}^{2+}_{(\text{aq})} ; \text{E}^\circ = -0.03\text{ V}$ $\text{Here, E}^\circ \text{ for the overall reaction is negative. Hence, the reaction between Ag}_{(\text{s})} \text{ and Fe}^{3+}_{(\text{aq})} \text{ is not feasible.}$

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Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}