electrochem Flashcards
What is oxidation?
The process where an atom or ion loses one or more electrons.
What is reduction?
The process where an atom or ion gains one or more electrons.
What is an oxidizing agent?
A substance that accepts electrons from another substance.
What is a reducing agent?
A substance that donates electrons to another substance.
What is the oxidation number of an atom in its elemental form?
Zero.
What is the oxidation number of oxygen in peroxides?
-1
What is the oxidation number of sulfur in H₂SO₄?
6
How do you calculate the oxidation number of an ion?
Equal to the charge of the ion.
What are the methods to balance redox reactions?
Oxidation number method and ion-electron method.
What is electrolytic conduction?
Conduction of electricity through an electrolyte leading to a chemical reaction.
What is molar conductivity?
The conductivity of a solution divided by the molar concentration of the electrolyte.
How does dilution affect molar conductivity?
Dilution increases molar conductivity by allowing ions to move more freely.
What is the difference between electrolytic and galvanic cells?
Electrolytic cells use electrical energy to drive a non-spontaneous reaction, while galvanic cells generate electrical energy from a spontaneous reaction.
What is Faraday’s first law of electrolysis?
The amount of substance deposited or liberated at an electrode is proportional to the electric charge passed.
What is Faraday’s second law of electrolysis?
The mass of a substance deposited or liberated at an electrode is proportional to its equivalent weight.
What is standard electrode potential?
The voltage developed by an electrode in a half-cell under standard conditions.
What is the standard hydrogen electrode (SHE)?
A reference electrode used to measure the electrode potentials of other half-cells, with a potential of 0 V.
What is the electrochemical series?
A list of elements arranged in order of their standard electrode potentials.
How does concentration affect electrode potential?
According to the Nernst equation, electrode potential is influenced by the concentration of ions.
What is the Nernst equation?
The equation that relates the electrode potential to the concentration of ions in the redox reaction.
What is the relationship between emf and Gibbs energy change?
ΔG = -nFE, where ΔG is the Gibbs free energy change, n is the number of electrons, F is Faraday’s constant, and E is the emf.
What is the effect of dilution on the conductivity of an electrolyte?
Dilution decreases the conductivity as the ions become further apart, reducing their ability to carry current.
What is the relationship between current and voltage in an electrolytic cell?
The current is directly proportional to the voltage applied across the cell.
What is the purpose of the electrolyte in an electrolytic cell?
The electrolyte provides ions that can move and carry charge, completing the electrical circuit.
What is the role of electrodes in an electrolytic cell?
Electrodes serve as surfaces for the oxidation and reduction reactions during electrolysis.
What is the difference between primary and secondary batteries?
Primary batteries are non-rechargeable, while secondary batteries can be recharged and used multiple times.
What is a salt bridge in a galvanic cell?
A salt bridge maintains electrical neutrality by allowing the flow of ions between two half-cells.
What is the function of a voltmeter in an electrochemical cell?
A voltmeter measures the electric potential (voltage) between two electrodes in a cell.
How do you calculate the cell potential of a galvanic cell?
Cell potential is calculated as the difference between the reduction potentials of the cathode and anode.
What does a positive electrode potential indicate?
A positive electrode potential indicates that a species is more likely to be reduced.
What does a negative electrode potential indicate?
A negative electrode potential indicates that a species is more likely to be oxidized.
What is the effect of temperature on electrode potential?
Temperature can influence the electrode potential by altering the kinetic energy of ions and the equilibrium of redox reactions.
What is the significance of a standard electrode potential of 0 V?
The standard electrode potential of 0 V is assigned to the standard hydrogen electrode (SHE), which is used as a reference.
How do you predict the products of electrolysis?
The products of electrolysis depend on the type of electrolyte, the electrode materials, and the voltage applied.
What is the relationship between the Gibbs free energy and the emf of a cell?
ΔG = -nFE, where ΔG is Gibbs free energy, n is the number of moles of electrons, F is Faraday’s constant, and E is the emf.
What is the Nernst equation used for?
The Nernst equation is used to calculate the electrode potential at non-standard conditions.
What is the effect of concentration on electrode potential?
The concentration of ions in solution influences the electrode potential, as described by the Nernst equation.
What is the significance of the electrochemical series?
The electrochemical series helps in predicting the direction of redox reactions and determining the standard electrode potentials.
What is a galvanic cell?
A galvanic cell is a device that generates electrical energy from spontaneous chemical reactions.
What is the role of the anode in an electrolytic cell?
The anode is the electrode where oxidation occurs in an electrolytic cell.
What is the role of the cathode in an electrolytic cell?
The cathode is the electrode where reduction occurs in an electrolytic cell.
What is the Nernst equation used for in numerical problems?
To calculate the electrode potential at non-standard conditions using ion concentrations.
How do you calculate the electrode potential using the Nernst equation?
E = E° - (0.0591/n) log [products/reactants], where n is the number of electrons transferred.
How does increasing ion concentration affect electrode potential?
Increasing ion concentration of the reduced species increases the electrode potential.
How does decreasing ion concentration affect electrode potential?
Decreasing ion concentration of the reduced species decreases the electrode potential.
Predict the electrolysis product of molten NaCl.
At cathode: Na(s), at anode: Cl₂(g).
Predict the electrolysis product of aqueous NaCl.
At cathode: H₂(g), at anode: Cl₂(g), as water is preferentially reduced.
Predict the electrolysis product of CuSO₄ solution with copper electrodes.
At cathode: Cu(s) deposition, at anode: Cu dissolves as Cu²⁺.
Predict the electrolysis product of CuSO₄ solution with platinum electrodes.
At cathode: Cu(s) deposition, at anode: O₂(g) from water oxidation.
What is the relationship between Gibbs free energy and equilibrium constant?
ΔG° = -RT ln K, where K is the equilibrium constant.
How can the standard emf of a cell be used to determine its spontaneity?
If E°cell > 0, the reaction is spontaneous; if E°cell < 0, the reaction is non-spontaneous.
How does temperature affect the Nernst equation?
Temperature changes the value of electrode potential by affecting reaction equilibrium.
What is an application of electrolysis in industry?
Production of aluminum from bauxite using the Hall-Héroult process.
What is an example of corrosion as a redox reaction?
Rusting of iron: Fe oxidizes to Fe²⁺ and further to Fe₃O₄ in presence of water and oxygen.
How can electrochemical principles be used to prevent corrosion?
Cathodic protection using sacrificial anodes like Zn or Mg.
What is a fuel cell?
An electrochemical device that converts chemical energy from fuel into electricity.
What is the main reaction in a hydrogen fuel cell?
2H₂ + O₂ → 2H₂O + energy, producing electrical power.
What is the significance of standard hydrogen electrode in electrochemistry?
It is used as a reference electrode with a defined potential of 0V.
What is the Faraday constant and its value?
The charge carried by 1 mole of electrons, approximately 96485 C/mol.
What is the unit of conductivity in SI units?
Siemens per meter (S/m).
How does the number of electrons transferred affect the Nernst equation?
Higher n values make electrode potential less sensitive to concentration changes.
