This site is 100% ad supported. Please add an exception to adblock for this site.

Chemistry - Redox Reactions and Electrochemistry


undefined, object
copy deck
What does the law of conservation of charge say?
It says that an electrical charge can be neither created nor destroyed
What is oxidation?
The loss of electrons
What is reduction?
The gain of electrons
What does this law imply about oxidation and reduction?
An isolated loss or gain of electrons cannot occur, but they must occur simultaneously, resulting in an electron transfer called a redox reaction
What is an oxidizing agent?
It causes another atom in a redox reaction to under oxidation, and is itself reduced
What is a reducing agent?
It causes the other atom to be reduced, and is it oxidized
What are oxidation numbers?
They are assigned to atoms in order to keep track of the redistribution of electrons during a chemical reaction
What is it possible to determine from the oxidation numbers of the reactants and products?
It is possible to determine how many electrons are gained or lost by each atom
What are the rules for oxidation numbers?
The oxidation number of free elements is zero, ex. N2, P4, S8 have zero oxidation numbers. The oxidation number for a monatomic ion is equal to the charge of the ion
What is the half-reaction method?
It is the most common method for balancing redox equation
What is it also known as?
It is also known as the ion-electron method
What are the steps?
Separate the two half reactions. Balance the atoms of each half reaction. First balance all atoms except H and O. In an acidic solution, add H2O to balance the O atoms, and then add H+ to balance the H atoms. In a basic solution, use OH- and H2O to balance the Os and Hs. Balance the charges of each half-reaction
What are galvanic cells?
They are also known as voltaic cells, and they are one of the two types of electrochemical cells. Galvanic cells are spontaneous
Where do nonspontaneous reactions take place?
They take place in electrolytic cells
The electrode at which oxidation occurs is called what?
It is called the anode
What is the electrode where reduction occurs?
It is called the cathode
Does a redox reaction occurring in a galvanic cell have a negative G or a positive G?
It has a negative G
What are galvanic cell reactions used for?
They supply energy and are used to do work
How can the energy be harnessed?
It can be harnessed by placing the oxidation and reduction half-reactions in separate containers called half-cells
How are the half-cells connected?
They are connected by an apparatus that allows for flow of electrons
What does a salt bridge do?
A salt bridge allows the charge gradient to be dissipated, which permits the exchange of cations and anions
What does a salt bridge usually contain?
It usually contains an inert electrolyte, usually KCL or NH4NO3, whose ions will not react with the electrodes or with the ions in solution
Which direction do electrons flow?
They flow from the anode through the wire and the voltmeter toward the cathode
What is a cell diagram?
It is a shorthand notation representing the reactions in an electrochemical cell
What are the rules used in constructing a cell diagram?
The reactants and products are always listed from left to right in the form: Anode | anode solution || cathode solution | cathode. A single vertical line indicates a phase boundary. A double vertical line indicates the presence of a salt bridge or some other type of barrier
How are the oxidation and reduction half-reactions usually placed in an electrolytic cell?
They are usually placed in one container
What did Faraday say about the behavior of electrolytic cells?
He said that the amount of chemical change induced in an electrolytic cell is directly proportional to the number of moles of electrons that are exchanged during a redox reaction
What does one electron carry the charge of?
It carries it as 1.6x10-19 coulombs ©
What is one Faraday (F) equal to?
It is equivalent to the amount of charge contained in one mole of electrons
What is it?
1F = 96,487 coulombs, or J/V
What is the anode of an electrolytic cell considered?
It is considered positive
Because the spontaneous oxidation reaction that takes place at the galvanic cell’s anode is the original source of that cell’s negative charge
What is the anode of a galvanic cell considered?
It is considered negative
What does this mean?
It means it is the source of electrons
Where does oxidation take place in both types of cells?
It takes place at the anode
How do electrons always flow through the wire?
They always flow through the wire from the anode to the cathode
In a galvanic cell, how is charge spontaneously created?
It is spontaneously created as electrons are released by the oxidizing species at the anode
In an electrolytic cell, where are the electrons forced through?
They are forced through the cathode where they encounter the species which is to be reduced
What is it here that provides electrons?
The cathode provides electrons
What does this make the cathode of an electrolytic cell?
It is considered the negative electrode
What is the mnemonic that shows what a cathode attracts?
A CAThode attracts CATions
What allows you to determine which species in a reaction that will be oxidized or reduced?
The reduction potential of each species
What is this defined as?
It is defined as the tendency of a species to acquire electrons and be reduced
What is the standard hydrogen electrode?
It is what all reduction potentials are judged against. It is given a potential of 0.00 volts
What is the standard reduction potential?
It is measured under standard conditions: 25C, a 1M concentration for each ion participating in the reaction, a partial pressure of 1 atm for each gas that is part of the reaction, and metals in their pure state
What can the relative reactivity’s of different half-cells be compared to predict?
They can be compared to predict the direction of electron flow
What does a higher E mean?
It means a greater tendency for reduction to occur
What does a lower E mean?
It means a greater tendency for oxidation to occur
What are standard reduction potentials also used to calculate?
The standard electromotive force of a reaction
What is that?
It is the difference in potential between two half-cells
What is the EMF of a reaction?
It is determined by adding the standard reduction potential of the reduced species and the standard oxidation potential of the oxidized species
Do you multiply the number of moles oxidized or reduced when adding standard potentials?
If the EMF is negative, is the cell an electrolytic or galvanic cell?
If the EMF is negative, it is electrolytic

Deck Info