Electrochemistry and Nernst Equation

Electrochemistry

• Cu(s) will react with a solution containing AgNO3(aq) resulting in a blue solution. This is because Cu is more reactive than silver and will displace silver ions from the solution, forming Cu2+(aq) ions which have a blue color.
• Zn(NO3)2(aq), Mg(NO3)2(aq), and KNO3(aq) will not react with Cu(s) and therefore will not turn blue. These metals are less reactive than copper and will not displace copper ions from solution.

Nernst Equation

• The Nernst Equation relates the cell potential (E) of an electrochemical cell to the standard cell potential (E°), the temperature (T), and the concentrations of the reactants and products.
• For the reaction: Cl2(g) + 2Br–(aq) → 2Cl–(aq) + Br2(l)
• E° = 0.29 V
• [Cl–] = [Br–] = 0.01 M
• P(Cl2) = 0.25 atm
• The cell potential can be calculated using the Nernst equation: E = E° – (RT/nF)lnQ
• E = 0.29 V – (8.314 J/mol·K × 298 K / (2 × 96485 C/mol) × ln(0.01² / 0.25))
• E = 0.272 V

Electrochemical Cells

• Standard cell potential (E°) for the reaction Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) is 1.10 V at 25°C.
• The standard cell potential represents the difference in potential between the two half-cells under standard conditions (1 atm pressure, 298 K, and 1 M concentration).
• The positive value of E° indicates that the reaction is spontaneous under standard conditions.

Electrolysis

• The process of electrolysis involves using an external electric current to drive a non-spontaneous chemical reaction.
• In the electrolysis of a solution containing Al3+(aq) and SO2–4(aq), H2(g) is liberated at the cathode and Cl2(g) is liberated at the anode.
• This indicates that the reduction of H+ ions to H2(g) occurs at the cathode, while the oxidation of Cl– ions to Cl2(g) occurs at the anode.

Molar Conductivity

• Molar conductivity (Λm) is a measure of the conductivity of an electrolyte solution per unit concentration.
• The limiting molar conductivity (Λo) refers to the molar conductivity at infinite dilution.
• Limiting molar conductivity can be determined using the Kohlrausch's Law, which states that the limiting molar conductivity of a strong electrolyte is the sum of the limiting molar conductivities of its individual ions.

Thermodynamic Efficiency

• The thermodynamic efficiency of a cell is the ratio of the Gibbs Free Energy change (ΔG) to the maximum electrical work (Wmax) that can be obtained from the cell.
• ΔG = -nFE°
• where n is the number of moles of electrons transferred, F is the Faraday constant, and E° is the standard cell potential.
• Wmax = -ΔG

Electrochemical Series

• The electrochemical series is a list of elements arranged in order of their standard reduction potentials.
• The reducing power of a metal is directly related to its ability to lose electrons.
• Metals higher in the electrochemical series have a greater tendency to lose electrons and are therefore stronger reducing agents.
• The correct decreasing order of reducing power of the metals is: K > Al > Cr > Ag

Electrolysis Calculations

• The quantity of electricity required to completely oxidize a certain amount of a substance can be calculated using Faraday's Law of Electrolysis.
• Faraday's constant (F) is the charge carried by one mole of electrons, which is 96485 C/mol.
• To oxidize 0.1 mol of MnO42– to MnO4–, one mole of electrons needs to be transferred per mole of MnO42–.
• Therefore, the quantity of electricity required is 0.1 mol × 96485 C/mol = 9648.5 C.

This quiz explores the principles of electrochemistry, focusing on the reaction between copper and silver ions, and the use of the Nernst Equation to calculate cell potentials. Test your understanding of the reactivity of metals and the relationship between cell potential and concentration. Perfect for students in chemistry courses.