Exam #3 Review (CH16&17)

Equations

100

What is the equation for calculating E⁰_cell from a standard reduction potentials chart?

E⁰_cell = E⁰_red + E⁰_ox

E⁰_cell = E⁰_cathode - E⁰_anode

200

What is (delta)S_univ = to? 

(delta)S_univ = (delta)S_sys + (delta)S_surr

300

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

T_eqbm = (delta)H/(delta)S

400

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

500

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?  

E_cell = E⁰_cell - (RTlnQ/nF) 

E_cell = E⁰_cell - (0.0592logQ/n)

Bonus: 

(delta)G = -nFE_cell

(delta)G⁰ = -nFE⁰_cell

Thermo Basics

100

For any spontaneous reaction (delta)S must be ? 

And (delta)G must be? 

(delta)S > 0, (positive) 

(delta)G < 0, (negative) 

200

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)

300

Phase changes represent what? 

Equilibrium processes. Which also means we can calculate T_eqbm

400

What are the signs of (delta)H & (delta)S that make a reaction spontaneous at all temps?

(delta)H = - (negative) 

(delta)S = + (positive) 

500

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

Electrochem Basics

100

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

200

In a Voltaic and Electrolytic cell oxidation and reduction take place at which electrodes? 

Oxidation at anode (ox - an)

Reduction at cathode (red-cat) 

300

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

400

Answer the following about concentration cells: 

a) Which value needs to be smaller, [M]_Anode or [M]_Cathode in order to produce a positive E_cell value (spontaneous process)? 

b) what will the nernst equation look like for a concentration cell? 

a) [M]_Anode < [M]_Cathode

b) E_cell = (-0.0592/n)log([M]_A/[M]_C)

500

 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.

Reduction Chart Components

100

All reactants in a reduction chart are? 

Oxidizing Agents

200

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

300

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

400

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"

500

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 

Molten/Aqueous Salts & Electroplating

100

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

200

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

300

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) 

400

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 

500

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^-   E⁰_red= -0.83

Oxidation: 

2H₂O(l) ---> O₂(g) + 4e^- + 4H⁺    E⁰_ox = -1.23