Redox Rxns
Oxidation States
1/2 Reactions
Voltaic Cells & Reduction Potential
Review
100
What is a redox reaction?
A transfer in electron density - can be determined by analyzing the oxidation states.
100
If something is oxidized, does its oxidation state increase or decrease? Will the electron density increase or decrease?
Oxidation state increases because the electron density decreases.
100
What are the steps in balancing redox reactions?
1. Determine oxidation states
2. Write the half reactions
3. Balance the atoms that change their oxidation states and determine the number of electrons gained or lost
4. Balance the number of electrons transferred
5. Cancel out common terms in the overall equation
100
What is the mnemonic device to remember cathodes and electrodes?
An Ox
Red Cat
100
What is the most important trend when determining the strength of an acid?
Size and EN
200
What species gets reduced in the following equation?
Cr+ + Sn4+ 
Sn
200
What are the oxidations states in the following reaction?
Cr2O72- (aq) + 2OH- (aq) → 2CrO42- (aq) + H2O (l)
They are all the same - no redox
200
What are the half reactions from the following redox reaction?
MnO4- (aq) + Cl- (aq) -> Mn2+ (aq) + HClO (aq)
MnO4- (aq) -> Mn2+ (aq)
Cl- (aq) -> HClO (aq)
200
What is the function of a salt bridge?
Allows the ions to move depending on the difference charges in the anode/cathode.
200
If you are given a table of data, how can you tell what order the reaction is?
Graph it. If it is a straight line already, it is 0th order. If it is not a straight line, take the natural log of the y-values. If this makes it a straight line, it is 1st order. If it is still not straight, take the inverse of it. If this is straight, it is 2nd order.
300
What is the reducing agent in the following equation?
Cd(s) + NiO2(s) + 2 H2O(l) → Cd(OH)2(s) + Ni(OH)2(s)
Cd
300
What are the oxidation states in the following molecule?
Cr(H2O)63+
O: -2
H: +1
Cr: +3
300
What is the one half reaction that will NOT occur in the following redox reaction? Why?
Al (s) + 2H+ (aq) + 2Cl- (aq) → Al3+ (aq) + H2 (g) + 2Cl- (aq)
2Cl- -> 2Cl-
These are spectator ions and do not participate in the reactions since they are neither oxidized or reduced.
300
For a strong reducing agent, do you want a high or low electrochemical cell potential value?
Low. The more negative the E value is, the better reducing agent it is.
300
What is the difference between enthalpy and entropy?
Enthalpy is the amount of internal energy (heat) contained in a compound whereas entropy is the amount of disorder (chaos) within the compound.
400
Would you need an oxidizing or reducing agent for the following reaction to occur?
Al(s) → Al(OH)4-
Oxidizing
400
What are the oxidation states of this molecule?
Fe3O4
O: -2
Fe: +8/3
400
Balance the following redox reaction:
Co3+(aq) + Ni(s) → Co2+ (aq) + Ni2+(aq)
2Co3+(aq) + Ni(s) → 2Co2+ (aq) + Ni2+(aq)
400
Identify the reactions at the anode and cathode of an electrochemical cell composed of these two half cells:
Cu(s)/Cu2+(aq)
Zn(s)/Zn2+(aq)
Cu: Cathode
Zn: Anode
400
If the pKb for a conjugate acid/base pair is 10, what is the Ka value for this pair?
Ka = 0.0001
500
Is the following reaction oxidation or reduction? *see attached page*
Reduction!
500
Which of the following is the most reduced?
a. CO2
b. CH3COCH3
c. CH2CH2
d. CH3CH3
d. CH3CH3 (ethane)
500
Balance the following redox reaction:
Al (s) + 2H+ (aq) + 2Cl- (aq) → Al3+ (aq) + H2 (g) + 2Cl- (aq)
2Al (s) + 6H+ (aq) → 2Al3+ (aq) + 3H2 (g)
500
Determine delta V for the following cell:
Cu(s)/Cu2+(aq)
Zn(s)/Zn2+(aq)
1.1 V
500
If 0.82M HBr dissociates into 0.22M Br- and 0.31M H3O+, what is the pKa of the reaction?
pKa = 1.08