Electrochemistry stuff Flashcards
what is the formula for charge in Coulombs (C)?
q=It
q = charge in Coulombs (C)
I = current in C/s or Amperes (A)
t = time in seconds (s)
What are the two different formulas for the number of moles of electrons (mol)?
nₑ₋ = q/F
nₑ₋ = It/F
nₑ₋ = number of moles in electrons (mol)
q = charge in Coulombs (C)
F = Faraday Constant (C/mol)
I = current in C/s or Amperes (A)
t = time in seconds (s)
what is Faraday’s constant (F)?
9.65 x 10⁴ C (also in data booklet)
Which of the following reactions are redox reactions and which aren’t?:
Formation, Single Replacement, Double Replacement, Combustion,
The formation reaction is a redox reaction
A single Replacement reaction is a redox reaction
A double replacement reaction is not a redox reaction
A combustion reaction is a redox reaction
For a non-spontaneous reaction, do we need a power source/supply?
YES
what ion is an exception to our theoretical rules for determining the strongest reducing agent?
chlorine (ions), water is the stronger RA BUT chloride ions are chosen because the transfer of e- from H2O to O2 is more difficult.
what is overvoltage?
Overvoltage is often encountered in electrolysis and battery charging processes. It can be thought of as the “extra push” needed to overcome certain barriers, such as the energy needed to initiate a reaction or overcome resistive losses in the material.
____ will speed up the oxidation by acting as a salt bridge?
salt
what are some clues to know if oxidation is happening? (just list brief descriptions and read)
- Understanding Oxidation-Reduction (Redox) Reactions:
An oxidation-reduction (redox) reaction involves the transfer of electrons between two substances. The substance that loses electrons is oxidized, while the substance that gains electrons is reduced. - Oxidation States:
The oxidation state of an element in a compound represents the hypothetical charge that atom would have if all bonds to atoms of different elements were 100% ionic. Comparing the oxidation states of an atom before and after the reaction can help you identify if oxidation has occurred.
Here’s how to calculate the oxidation state:
The oxidation state of a free element (not combined with any other element) is 0.
The oxidation state of a monatomic ion is equal to its charge.
Oxygen is usually -2 in its compounds, except in peroxides where it is -1.
Hydrogen is +1 when combined with non-metals, -1 when combined with metals.
The sum of oxidation states of all atoms in a compound is 0, and in an ion, it equals the ion’s charge.
3. Identifying Oxidation in a Chemical Reaction:
If an atom’s oxidation state increases in a reaction, that atom is being oxidized. For example, in the reaction 2Fe + 3O2 -> 2Fe2O3, the oxidation state of Fe increases from 0 to +3. Therefore, Fe is oxidized.
- Understanding Oxidizing Agents:
An oxidizing agent causes another substance to be oxidized by accepting electrons from that substance. In the process, the oxidizing agent is reduced. Common oxidizing agents include oxygen, hydrogen peroxide, and halogens. - Use of Half-reactions:
Half-reactions are a useful tool to help visualize the oxidation and reduction parts of a redox reaction. An oxidation half-reaction shows what’s happening to the species being oxidized, while a reduction half-reaction shows what’s happening to the species being reduced. - Balancing Redox Reactions:
This is important when you’re working with chemical reactions in a lab or in industry. Balancing redox reactions ensures that the number of atoms and the amount of charge is the same on both sides of the reaction. The steps to balance redox reactions include identifying the species being oxidized and reduced, balancing atoms other than O and H, balancing O atoms by adding H2O, balancing H atoms by adding H+, and checking that the electrons gained in the reduction equals the electrons lost in the oxidation.
Remember that oxidation can’t happen without reduction - they’re two sides of the same process. A substance can only lose electrons (be oxidized) if another substance gains those electrons (is reduced).
chemical reactions which occur on their own without the input of additional energy are called?
spontaneous
if there is a reaction, without additional energy then it is?
spontaneous
what are the steps to balancing reactions with half reactions
In acidic conditions:
balance all atoms, other than O and H
balance O by adding H2O
balance H by adding H+
balance the charge by adding e-
in basic solutions:
do the steps above, except for adding e-
add OH- to both sides to equal the number of H+
combine H2O
cancel H2O from both sides
For oxidation numbers, if the number decreases then _________ has occurred
reduction
For oxidation numbers, if the number increases then _________ has occurred
oxidation
Corrosion can be viewed as the process of metals returning to their _____________
The metal is oxidized causing the loss of structural _________
natural state (ore)
integrity
How does a coating of other metal protect metals you don’t want to corrode?
The coating of the metal is a stronger reducing agent than the metal that is to be protected. This coating metal will react instead and is called the sacrificial anode.
This process is called cathodic protection
when is the oxidation number of oxygen -1?
the oxidation number for oxygen is only -1 in peroxides(H₂O₂, Na₂O₂). Otherwise, it is -2
