A voltaic cell is constructed with two $\mathrm { Zn } ^ { 2 + }$ -Zn electrodes,where the half-reaction is $\quad$
$\quad$ $\mathrm { Zn } ^ { 2 + }$ + $2 \mathrm { e } ^ { - }$ ? Zn (s) $\quad$ $\quad$ E° = -0.763 V The concentrations of zinc ion in the two compartments are 1.17 × $10 ^ { - 2 }$ mol L^-1 and 8.70 × $10 ^ { - 2 }$ mol L^-1,respectively.The cell emf is ________ V.

Question

A voltaic cell is constructed with two

\mathrm { Zn } ^ { 2 + }

-Zn electrodes,where the half-reaction is

\quad

\quad

\mathrm { Zn } ^ { 2 + }

+

2 \mathrm { e } ^ { - }

? Zn (s)

\quad

\quad

E° = -0.763 V The concentrations of zinc ion in the two compartments are 1.17 ×

10 ^ { - 2 }

mol L^-1 and 8.70 ×

10 ^ { - 2 }

mol L^-1,respectively.The cell emf is ________ V.

Quizplus · Accepted Answer

The Nernst equation is:$$E = E° - \frac{RT}{nF} \ln Q$$where:* E is the cell emf* E° is the standard cell emf* R is the gas constant (8.314 J/mol·K)* T is the temperature in Kelvin* n is the number of moles of electrons transferred in the balanced redox reaction* F is the Faraday constant (96,485 C/mol)* Q is the reaction quotientIn this case, the balanced redox reaction is:$$\mathrm { Zn } ^ { 2 + }\) + $2 \mathrm { e } ^ { - }$ ? Zn (s)$$and the reaction quotient is:$$Q = \frac{[\mathrm { Zn } ^ { 2 + }]_{\text{cathode}}}{[\mathrm { Zn } ^ { 2 + }]_{\text{anode}}}$$Substituting the given values into the Nernst equation, we get:$$E = -0.763 V - \frac{(8.314 J/mol·K)(298 K)}{(2 mol)(96,485 C/mol)} \ln \frac{8.70 × 10^{-2} mol L^{-1}}{1.17 × 10^{-2} mol L^{-1}}$$$$E = -0.763 V - 0.0257 V$$$$E = -0.0850 V$$Therefore, the correct answer is E) 0.0850 V.

A Voltaic Cell Is Constructed with Two Zn2+\mathrm { Zn } ^ { 2 + }Zn2+

A Voltaic Cell Is Constructed with Two $\mathrm { Zn } ^ { 2 + }$