back to directory
NEET CHEMISTRYElectrochemistryMedium

Question

Given below are half-cell reactions: MnO4+8H++5eMn2++4H2O ;\EMn2+/MnO4=1.510 VMnO_4^- + 8H^+ + 5e^- \rightarrow Mn^{2+} + 4H_2O \ ; \E^\circ_{Mn^{2+}/MnO_4^-} = -1.510\text{ V} 12O2+2H++2eH2O ;\EO2/H2O=+1.223 V\frac{1}{2}O_2 + 2H^+ + 2e^- \rightarrow H_2O \ ; \E^\circ_{O_2/H_2O} = +1.223\text{ V} Will the permanganate ion, MnO4MnO_4^-, liberate O2O_2 from water in the presence of an acid?

A

No, because Ecell=2.733 VE^\circ_{cell} = -2.733\text{ V}

B

Yes, because Ecell=+0.287 VE^\circ_{cell} = +0.287\text{ V}

C

No, because Ecell=0.287 VE^\circ_{cell} = -0.287\text{ V}

D

Yes, because Ecell=+2.733 VE^\circ_{cell} = +2.733\text{ V}

Step-by-Step Solution

For MnO4MnO_4^- to liberate O2O_2 from water, MnO4MnO_4^- must undergo reduction and H2OH_2O must undergo oxidation.

Cathode (Reduction): MnO4+8H++5eMn2++4H2OMnO_4^- + 8H^+ + 5e^- \rightarrow Mn^{2+} + 4H_2O The given potential is for the reverse process (oxidation of Mn2+Mn^{2+}), so the standard reduction potential is: Ecathode=EMn2+/MnO4=(1.510 V)=+1.510 VE^\circ_{cathode} = -E^\circ_{Mn^{2+}/MnO_4^-} = -(-1.510\text{ V}) = +1.510\text{ V}

Anode (Oxidation): H2O12O2+2H++2eH_2O \rightarrow \frac{1}{2}O_2 + 2H^+ + 2e^- The standard reduction potential for oxygen is given as: Eanode=EO2/H2O=+1.223 VE^\circ_{anode} = E^\circ_{O_2/H_2O} = +1.223\text{ V}

The standard cell potential is: Ecell=EcathodeEanode=1.510 V1.223 V=+0.287 VE^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = 1.510\text{ V} - 1.223\text{ V} = +0.287\text{ V}

Since EcellE^\circ_{cell} is positive, the reaction is spontaneous. Therefore, the permanganate ion will liberate O2O_2 from water.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Electrochemistry. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYElectrochemistryhalfcellreactionsrightarrowecircmnmnorightarrow

More Electrochemistry Questions

View all

A cell reaction becomes spontaneous when:

A.$\Delta G^{\circ}$ is negative
B.$\Delta G^{\circ}$ is positive
C.$E^{\circ}_{Red}$ is positive
D.$E^{\circ}_{Red}$ is negative
EasySolve

In a typical fuel cell, the reactants (R) and products (P) are:

A.R = $H_2(g)$, $O_2(g)$; P = $H_2O_2(l)$
B.R = $H_2(g)$, $O_2(g)$; P = $H_2O(l)$
C.R = $H_2(g)$, $O_2(g)$, $Cl_2(g)$; P = $HClO_4(aq)$
D.R = $H_2(g)$, $N_2(g)$; P = $NH_3(aq)$
EasySolve

The cell reaction of an electrochemical cell is $Cu^{2+}(C_1) + Zn \rightarrow Cu + Zn^{2+}(C_2)$. The change in free energy will be the function of:

A.$\ln(C_1+C_2)$
B.$\ln(C_2/C_1)$
C.$\ln C_2$
D.$\ln C_1$
MediumSolve

The efficiency of a fuel cell is given by:

A.$\Delta H/\Delta G$
B.$\Delta G/\Delta S$
C.$\Delta G/\Delta H$
D.$\Delta S/\Delta G$
EasySolve

The number of Faradays (F) required to produce $20 \text{ g}$ of calcium from molten $\text{CaCl}_2$ (Atomic mass of Ca = $40 \text{ g mol}^{-1}$) is:

A.2
B.3
C.4
D.1
MediumSolve

For a cell involving one electron $E^\ominus_{\text{cell}} = 0.59 \text{ V}$ at $298 \text{ K}$. The equilibrium constant for the cell reaction is: [Given that $\frac{2.303 RT}{F} = 0.059 \text{ V}$ at $T = 298 \text{ K}$]

A.$1.0 \times 10^{30}$
B.$1.0 \times 10^2$
C.$1.0 \times 10^5$
D.$1.0 \times 10^{10}$
EasySolve

The value of $E^{\circ}_{cell}$ for the following reaction is: $Cu^{2+} + Sn^{2+} \rightarrow Cu + Sn^{4+}$ (Given, equilibrium constant is $10^6$)

A.0.17
B.0.01
C.0.05
D.1.77
MediumSolve

The three cells with their $E^{\circ}_{cell}$ values are given below: 1. $Fe|Fe^{2+}||Fe^{3+}|Fe \ ; \ 0.404\text{ V}$ 2. $Fe|Fe^{2+}||Fe^{3+}, Fe^{2+}|Pt \ ; \ 1.211\text{ V}$ 3. $Fe|Fe^{3+}||Fe^{3+}, Fe^{2+}|Pt \ ; \ 0.807\text{ V}$ The standard Gibbs free energy change values for three cells are, respectively: (F represents the charge on $1\text{ mole}$ of electrons.)

A.–1.212 F, –1.211 F, –0.807 F
B.+2.424 F, +2.422 F, +2.421 F
C.–0.808 F, –2.422 F, –2.421 F
D.–2.424 F, –2.422 F, –2.421 F
HardSolve

This neet chemistry practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice chemistry sets →