Electrochemistry Flashcards
What is the oxidation state of Hydrogen usually?
+1
What is the oxidation state of Oxygen usuallly?
2+
What is the oxidation number of an atom in a neutral element (group 8)?
zero
What is the oxidation state of any monatomic ion (ex. Na+, H+, Cl-, N3-)?
oxidation state = charge on the ion
In a neutral compound the oxidation numbers of all atoms … (ex. H2O)
add up to zero
In a polyatomic ion the oxidation numbers of all atoms …
add up to the charge on the ion
What elements can have a variery of oxidation #?
C, N, S, P, transition metals
What is the oxidation state of hydrogen in LiAlH4?
-1
What is the oxidation state of hydrogen in NaBH4?
-1
What is the oxidation state of oxygen in the peroxide H2O2?
-1
What oxidation number do halogens usually have?
-1 unless bonded with oxygen
What is the oxidation number of aluminum?
3+
How does the oxidation number change when an atom is oxidized?
Increses (becomes more positive)
How does the oxidation number change when an atom is reduced?
It decreases (becomes more negative)
Reducing agent
reactant providing/donating the electrons
Oxidizing agent
reactant taking the electrons away
What are the 4 steps/rules of balancing a half-reaction?
- balance the main atom first (Not H or O)
- Balance oxygen by adding H₂O to other side
- Balance hydrogens by adding H⁺ to the other side
- Balance the charge by adding electrons to the more positive side
When turning a balanced equation into a basic reaction you …
(To the final equation added together) add OH⁻ to each side of the equation for every H⁺ you have
Anode
Where oxidation occurs, where the electrons are coming from
Cathode
Where reduction occurs, where the electrons are going to
What do the double vertical line in the cell notation represent?
The salt bridge
What do the single vertical lines in cell notation represent?
Phase changes (s/aq)
Where is the anode in cell notation?
always on the far left
Where is the cathode in cell notation?
Always on the far right
What is the molarity if not specified in the cell notation?
1 M
The anode is always one ….
of the solid electrodes
What does E symbolize?
- electrical potentials/voltages
What does E° symbolize?
- electrical potentials under standard conditions
- potential for the reduction half-reaction minus the potential for the oxidation half-reaction
Galvanix/Voltaic cell
- spontaneous
- produces electricity
- E° is positive
Electrolytic cell
- non-spontaneous
- needs electricity as a reactant in order to procedd
- E° is negative
