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Level 129

Galvanic Cells

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A positive electrode
A negative electrode
from the anode to the cathode
Electrons in a galvanic cell flow from the _______ to the _______.
Cell Line Notation
Metal to be oxidized | Oxidized metal || Metal to be reduced (ion) | Reduced metal
Requires a difference in reactivity to take place
Why can the same metal not be used for the Anode and the Cathode of a Galvanic cell?
2e? from Anode travel to Cathode. 2e? combine with Cations in solution to form Metal on Cathode.
Describe what takes place at the Cathode of a Galvanic cell. The Cathode is Cu and the Anode is Zn.
What happens as the Cathode of a Galvanic cell is being Reduced? How is this counter-acted?
Cations(+) are removed from solution, thus a (-) charge builds up. Metal(+) from Salt bridge and Zn²? Cations from the Anode thus flow into Cathode beaker.
Anode loses 2e?, forming Cations(Zn²?) in solution.
Describe what takes place at the Anode of a Galvanic cell. The Cathode is Cu and the Anode is Zn.
What happens as the Anode of a Galvanic cell is being Oxidised? How is this counter-acted?
A (+) charge builds up, thus Anions(SO4²?) from salt bridge flow into beaker to balance the charge.
The oxidation and reduction half-cells.
What does the Salt bridge connect?
What is the function of the Salt bridge?
Maintains neutrality within the circuit, preventing the cell from rapidly reaching equilibrium.
What would happen if a Salt bridge was not present in a Galvanic cell?
The solutions in the half-cells would both accumulate a (+) or (-) charge, preventing further reaction.
is Inert, does not react with other chemicals in the cell
What can be said about the reactivity of the Electrolyte contained in the Salt bridge?
salt bridge
_______ allows ions to flow between the cells to balanced the charge in the half-cells.
anode cathode
Electrons flow from the _______ electrode to the _______ electrode. (terms)
black red
Electrons flow from the _______ electrode to the _______ electrode. (colors)
Electron Flow
goes from anode to cathode
Cation Flow
goes from anode to cathode
Anion Flow
goes from cathode to anode
A starting material in a chemical reaction
Oxidizing agent
An element/compound that's reduced.
Reducing agent
A reagent that reduces (adds electrons to) another species
Porous Disk
Cations and Anions
Define electric cell.
A device that continuously converts chemical energy into electrical energy.
What limitation did scientists face?
They could not put electricity to practical use until 1800 when Alessandro Volta invented the electric cell.
What were the electric cells used for?
To form a battery. This is because the electric cells produced very little electricity until they were joined together.
Describe the setup of Volta's cells.
His cells consisted of a layer of zinc metal separated from a layer of copper metal by paper soaked in salt water.
Describe the flow of current across these cells.
A steady electric current flower through a loop of wire attached to the top and bottom of a stack of cells, called a voltaic pile.
What is a cell composed of?
Two electrodes (solid conductors) and one electrolyte (aqueous conductor).
Two metals.
What type of metal are electrons usually?
What is the difference between cathode and anode?
A cathode is the positive electrode. The anode is the negative electrode.
How do electrons move?
Electrons move from the anode through conducting material to the cathode.
What impact does the design of the cell have?
The design of a cell results in electrons passing through an external circuit rather than directly from one substance to another.
How does one determine what happens in different parts of the cell?
Chemists use a different design separating the parts of the cell so they can be studied more easily.
What are the interactions between electrodes and electrolytes?
Each electrode is in contact with an electrolyte but the electrolytes surrounding each electrode are separated.
What purpose does a porous boundary serve?
A porous boundary (salt bridge) separates the electrolytes while still permitting ions to move between the solutions through tiny openings.
Define half-cell.
Each part is called a half-cell and consists of one electrode and one electrolyte.
Give two examples of half-cells.
Copper metal in a solution of copper ions. Zinc metal in a solution of zinc ions.
Describe cell notation.
Single line represents a phase boundary. Double line represents a physical boundary (salt bridge).
Define galvanic cell.
An arrangement of two half-cells that can produce electricity spontaneously.
Reduction at the cathode.
What does the SOA undergo?
Oxidation at the anode.
What does the SRA undergo?
What is notable about some oxidizing or reducing agents?
Some are ions in solution. For example, an acidic dichromate solution is an SOA that reacts with copper metal.
How may a cell be constructed?
Using a copper half-cell but an electrode is required for the dichromate half-cell.
Define inert electrode.
A solid conductor that will not react with any substances present in the cell (ex. carbon or platinum)
Define standard cell.
A galvanic cell in which each half-cell contains all entities shown in the half-reaction equations at SATP, with a concentration of 1.0 mol/L for all aqueous solutions.
Define standard cell potential.
?E° is the maximum potential difference (voltage) of the cell operating under standard conditions.
What does ?E° represent?
THe energy difference between the cathode and the anode.
What does ?E°r represent?
The ability of a standard half-cell to attract electrons, thus undergoing a reduction.
What is impossible with regards to ?E°r measurements?
To measure the ?E°r of a single half-cell because electron transfer requires both oxidation and reduction.
How are standard reduction potential assigned?
Relative to the hydrogen half-cell which is used as a reference and assigned an electrode potential of zero volts.