What is the equation for calculating E0cell from a standard reduction potentials chart?
E0cell = E0red + E0ox
E0cell = E0cathode - E0anode
For any spontaneous reaction (delta)S must be ?
And (delta)G must be?
(delta)S > 0, (positive)
(delta)G < 0, (negative)
a) Oxidation is ____ electrons and ______ in oxidation number?
b) Reduction is ____ electrons and ______ in oxidation number?
a)Loss of electrons
Inc. in oxidation number
b) Gain of electrons
Dec. in oxidation number
All reactants in a reduction chart are?
Oxidizing Agents
What is the very first step when we are dealing with Molten or Aqueous salts?
Ionization step! Where we break up our compund into its respective ions
What is (delta)Suniv = to?
(delta)Suniv = (delta)Ssys + (delta)Ssurr
If you were told to solve for the value of (delta)H & (delta)S for a certain reaction and were only given a list of values for each component of teh reaction, what method/equation would you use to solve for them?
Sum of Products(coeff) - Sum of reactants(coeff)
In a Voltaic and Electrolytic cell oxidation and reduction take place at which electrodes?
Oxidation at anode (ox - an)
Reduction at cathode (red-cat)
Match the letter to the blank:
1.The more positive the E value, the stronger the____?
2.The more negative the E value, the stronger the___?
a) Oxidizing Agent
b) Reducing Agent
1. a) oxidizing agent
2. b) reducing agent
In the electrolysis of molten salts the cation will be _____ and the anion will be ______.
cation will be reduced and anion will be oxidized
* (cation---->cathode & anion--->anode)
*we can use the same logic for aqueous salts, but there are a few exceptions, refer to CW 17.5-7 pg3
What is the equation for Gibbs Free Energy Change?
What is the equation for calculating the equilibrium temp?
(delta)G = (delta)H - T(delta)S
Teqbm = (delta)H/(delta)S
Phase changes represent what?
Equilibrium processes. Which also means we can calculate Teqbm
Answer the following about line notation?
a) By convention, what is written on the left and the right side?
b) If there is no metal on a side what do we do?
c)Why would we use a comma?
a) left - anode (ox.) & right - cathode (red.)
b) we add on platinum or graphite to the ends
c) To separate substances in the same phase
*if concentrations are given include in notation in () or else it is assumed to be 1M
With using the terms strong O.A., weak O.A., Strong R.A, and weak R.A write out how a spontaneous redox reaction will look like?
SOA + SRA ---> WOA + WRA
a) 1 Faraday's constant = ______C?
b) What is the equation to calculate Coulombs (C)?
a) 96,500 C
b) C = Current (amps) x Time (seconds)
What is the equation that relates (delta)G under standard and non-standard conditions?
What is it when at equilibrium?
(delta)G = (delta)G0 + RTlnQ
(delta)G0 = -RTlnK
What are the signs of (delta)H & (delta)S that make a reaction spontaneous at all temps?
(delta)H = - (negative)
(delta)S = + (positive)
Answer the following about concentration cells:
a) Which value needs to be smaller, [M]Anode or [M]Cathode in order to produce a positive Ecell value (spontaneous process)?
b) what will the nernst equation look like for a concentration cell?
a) [M]Anode < [M]Cathode
b) Ecell = (-0.0592/n)log([M]A/[M]C)
Will an oxidizing agent react with a reducing agent above it on the reduction potentials chart in order to produce a spontaneous reaction?
No, "A spont. rxn will occur between an O.A. and any R.A. that lies BELOW it"
How do we predict products for aqueous salts?
The 1/2 rxn with the most positive E0 value are favored therefore, that is how we predict which products are produced.
*Products for competing reactions are H2(g) for reduction & O2(g) for oxidation rxn
Nernst equation at any temp and then at 250C?
Bonus! - What are the equations for the Gibbs Free Energy Change under standard and non-standard conditions for redox reactions?
Ecell = E0cell - (RTlnQ/nF)
Ecell = E0cell - (0.0592logQ/n)
Bonus:
(delta)G = -nFEcell
(delta)G0 = -nFE0cell
Are the following scenarios examples of inc. entropy?
a) CO(g) + O2(g)---->CO2(g) + O(g)
b) MgCO3(s)--->MgO(g) + CO2(g)
c) Iron Melting
a) no, 2mol--->2mol of gas
b) Yes, solid to gas or increased number of particles
c) Yes, solid to liquid or low temp to higher temp
Voltaic/Galvanic/Daniel Cells:
a) Produces a ____ redox rxn ((delta)G ___0)
b) e-'s flow from _____ to _____
c) Anode is ___electrode & Cathode is ___electrode
Electrolytic Cell:
a) Produces a ____ redox rxn ((delta)G ___0)
b) e-'s flow from _____ to _____
c) Anode is ___electrode & Cathode is ___electrode
Voltaic:
a) spont., <
b)anode, cathode
c) neg. b/c e- produced, pos.
Electrolytic:
a) non-spont., >
b) cathode, anode
c) pos., neg.
Label the oxidation and reduction half reactions.
Sn2+ + 2e- ---> Sn(s) E0 = -0.14V
Ag+ + e- ---> Ag(s) E0 = 0.80V
Sn is oxidation reaction
Ag is reduction reaction
What are the two competing reactions for when we are dealing with aqueous salts? What are their E values?
Reduction:
2H2O(l) + 2e- ---> H2(g) + 2OH- E0red= -0.83
Oxidation:
2H2O(l) ---> O2(g) + 4e- + 4H+ E0ox = -1.23