A(voltaic) concentration cell is constructed using two zinc (zn) electodes and two aqueous solutions containing zn2+. if the concentrations of zn2+ in each of the two aqueous solutions are 1.25 m and 6.50 × 10-4 m, respectively, then the cell emf (ecell) is v.

a. −0.194
b. 0.194
c. −0.0972
d. 0.0972
e. 0.760

d. 0.0972

Explanation:

In a cell, a redox reaction happens, it means that one compound will reduce (gain electrons) and other will oxides (lose electrons). The reduction potential (E°) of a compound can be calculated by the redox between the compound and the hydrogen, which has E° = 0.00. As higher is the value of E°, as easy is for the compound to reduce. For a reaction, the value of E° = E° (the substance that reduces) - E°(the substance that oxides).

The cell emf can be calculated by the Nernst's equation:

Ecell = E° - (0.0592/n)*logQ

Where E° is the reduction potential of the cell (E°reduction - E°oxidation), n is the number of electrons being changing in the redox reaction, and Q is the reaction coefficient.

In this case, the cell is formed by the same compound, s E° = 0. Because Zn loses 2 electrons to form Zn⁺², n = 2, and the reaction must go from the highest concentration to the lowest, thus the reactant is where there's more Zn⁺², and the products where there's less Zn⁺²:

Q = [products]/[reactants]

Q = [Zn⁺²]less/[Zn⁺²]more

Ecell = -(0.0592/2)*log((6.50x10⁻⁴)/1.25)

Ecell = -0.0296*(-3.2840)

Ecell = 0.0972 V

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.