module 4 Flashcards
What are the components of a simple electric cell?
Two electrodes and one electrolyte
Differentiate between electric current and voltage
Electric current is the flow of electricity, measured in amps. Voltage is the force that pushes on the electric current, measured in volts.
What is a voltaic cell?
A device that converts chemical energy into electrical energy by reacting two different metals with an electrolyte
What is a half-cell?
One part of a voltaic cell that contains one electrode in an electrolyte solution
What is a porous boundary?
A barrier that allows the flow of ions, but prevents the mixing of the different substances
What is a salt Bridge?
A tube filled with an electrolyte solution that connects the 2 half cells and allows ions to flow.
What is an electrolyte?
Of substance that contains ions and conducts electricity
What is an external circuit?
The external path where electrons flow from the anode to the cathode like a wire
What is an inert electrode?
A conductor that does not participate in the chemical reactions (sometimes graphite)
What is the charge transfer?
The total charge moved by the cell (coulombs). Charge (Q) in coulombs = Current (I) in amperes × Time (t) in seconds. Q=It
What is power?
The rate at which a cell produces electrical energy (watts) current x voltage
What is energy density/specific energy?
How much energy a battery stores per unit mass j/kg
What is the the standard cell potential (E°cell)?
The standard cell potential (E°cell) is the maximum electric potential (voltage) difference under standard conditions, indicating the energy difference between the cathode and anode. Represents the difference in electron attraction ability between two half-cells.
What is a standard reduction potential (E°r)?
A standard reduction potential (E°r) shows a half-cell’s ability to attract electrons, with more positive values indicating a stronger attraction.
What is corrosion?
An electrochemical process where a metal is turned back into an ore like state after reacting with environmental elements like water.
What are the minimum requirements for the corrosion of iron?
The presence of water and oxygen
What are the two methods for preventing or minimizing the corrosion of iron?
- Barrier methods: using protective coatings like paint, tin, and zinc to prevent direct exposure to corrosive elements.
- Cathodic protection: iron is made the cathode by supplying electrons from a sacrificial anode (a metal that corrodes in place of iron)
What is the difference between an electrolytic cell and a voltaic (galvanic) cell?
Electrolytic: endothermic. Non-spontaneous. Negative cell potential. Cathode is the negative electrode, anode is the positive electrode. Electrical energy → chemical energy.
Voltaic (galvanic) cell: exothermic, spontaneous, positive cell potential. Cathode it’s the positive electrode and anode is the negative electrode.
Chemical energy → electrical energy
Describe the relationship of science and technology in the area of electrolysis. Include at least 2 examples in your description.
Voltas invention of the electric cell in 1800 led to the discovery that electric power could be used for electrolysis, revealing new elements. This shows how scientific discoveries enabled, technological, advancements in industries like metal refining, and plating.
1. Production of aluminum: aluminum was more expensive due to its high melting point but in 1886 Charles Hall and Paul Héroult discovered that dissolving aluminum oxide in molten cryolite, lowers the melting point, making electrolysis possible. This made aluminum more affordable.
2. Chlor-Alkali Process: this process uses electrolysis on brine (salt water) to make chlorine, hydrogen and sodium hydroxide. Improvements in membrane electrolytic cells have made this process more efficient, giving us high purity sodium hydroxide with little contamination.
State Faraday’s law
The mass of an element produced or consumed at an electrode is proportional to the time the cell operates, provided the current is constant
What is Faraday’s constant?
Faraday discovered that 9.65x10⁴C of charge is transferred per mole of electrons. This constant is used to convert charge to moles of electrons. F=9.65x10⁴ C/mol e⁻
Charge to Moles Conversion:
The amount of electrons (ne-) can be calculated as:
ne⁻=Q/F, ne⁻=It/F, where Q is the charge in coulombs, I is the current in amperes, and F is the Faraday constant.
