Make a sketch of a concentration cell employing two Zn/Zn2+ half-cells. The concentration of Zn2+ in one of the half-cells is 2.0 M and the concentration in the other half-cell is 1.0×10–3 M. Label the anode and the cathode and indicate the half-reaction occuring at each electrode. Also indicate the direction of electron flow.
Ch.19 - Electrochemistry
Chapter 19, Problem 81
A concentration cell consists of two Sn/Sn2+ half-cells. The cell has a potential of 0.10 V at 25°C. What is the ratio of the Sn2+ concentrations in the two half-cells?
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nernst Equation
The Nernst Equation relates the cell potential to the concentrations of the reactants and products in an electrochemical cell. It is expressed as E = E° - (RT/nF) ln(Q), where E is the cell potential, E° is the standard cell potential, R is the gas constant, T is the temperature in Kelvin, n is the number of moles of electrons transferred, F is Faraday's constant, and Q is the reaction quotient. This equation is essential for calculating the potential of concentration cells.
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Concentration Cell
A concentration cell is a type of electrochemical cell where both half-cells contain the same species but at different concentrations. The potential difference arises from the difference in concentration, driving the spontaneous flow of electrons from the higher concentration to the lower concentration. Understanding this concept is crucial for analyzing how concentration differences can generate electrical energy.
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Reaction Quotient (Q)
The reaction quotient (Q) is a measure of the relative concentrations of reactants and products at any point in a reaction. For a concentration cell involving Sn/Sn2+, Q is calculated as the ratio of the concentrations of Sn2+ in the two half-cells. This ratio is directly related to the cell potential, making it vital for determining the concentration difference that leads to the observed voltage.
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