The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al(s) + 3I₂(s) → 2Al³⁺(aq) + 6I^-(aq)
The emf generated by the cell when [Al³⁺] = 4.5 × 10^-3 mol L^-1 and [I^-] = 0.15 mol L^-1 is

Question

The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al(s) + 3I<sub>2</sub>(s) → 2Al<sup>3+</sup>(aq) + 6I<sup>-</sup>(aq) The emf generated by the cell when [Al<sup>3+</sup>] = 4.5 × 10<sup>-3</sup> mol L<sup>-1</sup> and [I<sup>-</sup>] = 0.15 mol L<sup>-1</sup> is A) 2.20 B) 2.32 C) 2.10 D) 2.39 E) 2.23

Quizplus · Accepted Answer

The Nernst equation can be used to calculate the cell potential at non-standard conditions:

E = E° - (RT/nF) * ln(Q)

where E is the cell potential, E° is the standard cell potential, 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 cell reaction (in this case, n = 6), F is the Faraday constant (96485 C/mol), and Q is the reaction quotient.

For the given cell reaction:

2Al(s) + 3I2(s) → 2AlI3(s)

The reaction quotient is:

Q = [AlI3]^2 / [I2]^3

At the given concentrations:

[AlI3] = 4.5 × 10^-3 M
[I2] = 0.15 M

So:

Q = (4.5 × 10^-3)^2 / (0.15)^3 = 3.6 × 10^-7

Substituting the values into the Nernst equation:

E = 2.20 V - (8.314 × 298 / (6 × 96485)) * ln(3.6 × 10^-7)

E = 2.32 V

Therefore, the best choice is B, with a cell potential of 2.32 V.

The Standard Emf for the Cell Using the Overall Cell