Given a cell based on the spontaneous reaction
2AgCl(s) + Zn(s) ® 2Ag(s) + 2Cl– + Zn2+
If the zinc ion concentration is kept constant at 1 M, and the chlorine ion concentration is decreased from 1 M to 0.001 M, the cell voltage should
increase by 0.06 V
increase by 0.18 V.
decrease by 0.06 V.
decrease by 0.18 V.
increase by 0.35 V.
Increase by 0.06 v
To determine the effect of changing the chlorine ion concentration on the cell voltage, we need to understand the Nernst equation and how it relates to the cell potential.
The Nernst equation is given by:
Ecell = E°cell - (0.0592/n) * log(Q)
Where:
Ecell is the cell potential
E°cell is the standard cell potential
n is the number of electrons transferred in the balanced equation
Q is the reaction quotient, which is the ratio of product concentrations to reactant concentrations raised to the power of their stoichiometric coefficients.
In this case, the spontaneous reaction is:
2AgCl(s) + Zn(s) → 2Ag(s) + 2Cl– + Zn2+
From the balanced equation, we can see that 2 moles of electrons are transferred. Therefore, n = 2.
Now, let's consider the concentrations and their effect on Q:
If the zinc ion concentration [Zn2+] is kept constant at 1 M, it does not affect Q since its concentration remains unchanged.
However, if the chlorine ion concentration [Cl–] is decreased from 1 M to 0.001 M, it affects Q. We can now determine the initial and final values of Q:
Initial Q = [product] / [reactant]
= (1 M)^2 / (1 M)^2
= 1
Final Q = [product] / [reactant]
= (1 M)^2 / (0.001 M)^2
= 1,000,000
Now, let's consider the effect of the change in Q on the Nernst equation for cell potential.
The Nernst equation can be rewritten as:
Ecell = E°cell - (0.0592/n) * log(Q)
Since Q is increasing significantly from 1 to 1,000,000, the logarithm term in the equation becomes larger. As a result, the cell potential decreases.
Therefore, the correct answer is:
The cell voltage should decrease by 0.06 V.