Chapter 19 Electrochemistry Flashcards by Serena Saechia

Define Oxidation Reduction Reaction

Reactions in which electrons transfer from one reactant to the other

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Define Oxidation

The loss of electrons

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Define Reduction

The gain of electrons

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The INCREASE in oxidation state of an atom is ____________

Oxidation

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The DECREASE in oxidation state of an atom is ____________

Reduction

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What is the oxidation state rule for a free element?

Oxidation state = 0

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What is the oxidation state rule for a monoatomic ion?

Oxidation state = its own charge

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What is the oxidation state rule for the same of oxidation states of neutral molecules and ions?

Neutral molecule oxidation state = adds up to 0

Ion oxidation state = adds up to its charge

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What is the oxidation state rule for metals in compounds in group 1A and 2A

Metal group 1A oxidation state = +1

Metal group 2A oxidation state = +2

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What is the oxidation state rule for nonmetals H and O?

H oxidation state = +1

O oxidation state = -2

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Assign oxidation states to the following...
I) Cl2 
II) Na+ 
III) KF 
IV) CO2 
V) FeSO4

I) 0 
II) +1 
III) 0 
IV) 0 
V) -2

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Assign oxidation states to the following...
I) Ag 
II) Fe3+ 
III) CH4 
IV) Cr2O7 2- 
V) ClO4 - 
VI) CaH2

I) 0 
II) +3 
III) C: -4, H: +1 
IV) Cr: +6, O: -2 
V) Cl: +7, O: -2 
VI) Ca: -2, H: +1

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Define Half-Reaction Balancing Method

A form of balancing redox reactions where you separate the overall equation into 2 half reactions

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Define Balancing Redox Reaction

When you balance both the mass and charge of the redox reactions

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What are the 2 half reactions for Half-Reaction Balancing Method?

Half for oxidation and half for reduction

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When balancing ACIDIC solutions, what do you add to balance O and H?

Add H2O to balance O and H+ to balance H

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When balancing BASIC solutions what is the additional step you must take?

Neutralize H+ by adding enough OH- to each H+ and add the same number of OH- ions to both sides

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Define Oxidizing Agent

A substance that causes the oxidation of another substance

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Define Reducing Agent

A substance that causes the reduction of another substance

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Oxidizing Agent is ____________, _______ electrons, and its oxidation state __________

Reduced; gains; decreases

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Reducing Agent is ____________, _______ electrons, and its oxidation state __________

Oxidized; loses; increases

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In the following reaction which element is the Reducing Agent and which is the Oxidizing Agent?
4 Na (s) + O2 (g) --> 2Na2O (s)

Na : Reducing Agent

O: Oxidizing Agent

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Define Electric Currents

The flow of electric charge

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What are the 2 ways electric currents are involved with chemical reactions?

I) Certain chemical reactions can product electricity

II) Electricity can make certain chemical reactions (nonspontaneous reactions) happen that would not happen otherwise

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Define Current

The number of electrons that flow through the system per second

The unit for Current is...

Ampere (A)

What are the 2 types of Electrochemical Cell types?

I) Voltaic (Galvanic) Cell | II) Electrolytic Cell

Define Voltaic (Galvanic) Cell

Electrochemical Cell that produces electrical current from a spontaneous chemical reaction

In Voltaic Cells, the _________ does work on the ___________ and creating ___________ is the desired outcome

System; surroundings; electricity

Define Electrolytic Cell

Electrochemical Cell that consumes electrical current to drive a nonspontaneous chemical reaction

In Electrolytic Cells, the _________ does work on the ___________ and creating ___________ is the desired outcome

Surroundings; system; chemical reactions

Define Cell Potential

The driving force (difference in potential energy) that pushes electrons away from the anode and pulls them toward the cathode

The __________ the Cell Potential, the ___________ the tendency of the redox reaction to occur spontaneously

Higher; greater

What does a negative Cell Potential indicate?

Indicates forward reaction is nonspontaneous

When cells are connected, electrons flow from electrode with more ____________ charge to more ____________ charge

Negative (greater potential energy); positive (less potential energy)

What are the components of a Voltaic (Galvanic) Cell?

2 half cells, 2 electrodes, 2 aqueous electrolyte solutions, wire connecting the electrodes and 1 salt bridge

Define Electrode

Conductive surfaces through which electrons can enter or leave the half cells

Define Anode

Electrode where OXIDATION occurs

Define Cathode

Electrode where REDUCTION occurs

T/F Electrons will flow from Cathode to Anode

False; Anode to Cathode

Define Half Cell

One half of an Electrochemical Cell where either oxidation or reduction occurs

Each Half Cell contains a conductive __________ and a surrounding conductive ____________

Electrode; electrolyte

Define Electrolyte

Substance that dissolves in water to form solutions that conduct electricity

Define Salt Bridge

U-shaped tube containing a strong electrolyte to complete the circuit by flowing ions to neutralize the charge buildup in the Half Cells

Identify and label the following in this Electrochemical Cell Notation... Anode | Electrolyte || Electrolyte | Cathode I) Identify what the single lines represent II) Identify what the double lines represent III) Identify the Oxidation half and Reduction half

I) Different phases II) Salt bridge III) Oxidation first half (anode), Reduction second half (cathode)

What does an Electrochemical Cell Notation look like when comparing reactants/products that are in different phases?

Ex. Anode | Electrolyte || Electrolyte | Cathode

What does an Electrochemical Cell Notation look like when comparing reactants/products that are in the same phase?

Ex. Fe (s) | Fe2+ (aq) || MnO4- (aq), H+, Mn2+ (aq) | Pt (s)

Identify and label the following in this Electrochemical Cell Notation... Fe (s) | Fe2+ (aq) || MnO4- (aq), H+, Mn2+ (aq) | Pt(s) I) Identify what Fe (s) represents II) Identify what the single lines represent III) Identify what the comma represents IV) Identify what Pt (s) represents

I) Electrode II) Different phases III) Same phases IV) Inert electrode

Electrons travel from ________ to _________

Anode; Cathode

We define E^o Cell as difference in voltage between final State (________) and initial state (_________)

Cathode; Anode

E^o Cell > 0 is spontaneous or nonspontaneous, as well as what type of cell?

Spontaneous; Voltaic Cell

E^o Cell < 0 is spontaneous or nonspontaneous, as well as what type of cell?

Nonspontaneous; Electrolytic Cell

Define Standard Cell Potential (E^o Cell)

Cell potential at standard conditions

Cathode is an electrode with _______ positive E^o and has greater tendency to undergo ___________

More; reduction

Anode is an electrode with ________ positive E^o and has greater tendency to undergo ___________

Less; oxidation

More positive E^o is easier for __________, greater _________ to electrons and stronger ___________ agent

Reduction; attraction; oxidizing

Less positive E^o is easier for ___________, greater _________ to electrons and stronger ___________ agent

Oxidation; repulsion; reducing

Define Standard Hydrogen Electrode (SHE)

This electrode has an arbitrary of 0.00 V which serves as a reference potential for all other half-cell reactions

What does ΔG^o, E^o cell and K have to be to be considered spontaneous?

ΔG^o < 0 E^o cell > 0 K > 1

What does ΔG^o, E^o cell and K have to be to be considered nonspontaneous?

ΔG^o > 0 E^o cell <0 K < 1

What is the equation used to compare Cell Potential (E^o Cell) and Free Energy (ΔG^o)?

ΔG^o = -nF E^o cell

What does "F" represent in the equation used to compare Cell Potential and Free Energy? ΔG^o = -nF E^o cell

Faraday's constant (96485 C/mol e-)

What are the 2 equations used to compare Cell Potential (E^o Cell) and K? (At standard conditions and at given conditions)

Given conditions: E^o cell = RT/nF (lnK) | Standard conditions: E^o cell = 0.0592V/n (logK)

What is the equation used for Cell Potential at nonstandard conditions?

Nernst Equation Given conditions: Ecell = E^o cell - RT/nF (lnQ) Standard conditions: Ecell = E^o cell - 0.0592V/n (logQ)

Define Electrolysis

The process by which electrical current is used to drive a nonspontaneous reaction

Define Electrolytic Cell

An electrochemical cell that uses external electrical current to drive a nonspontaneous reaction

Cations are __________ at the Cathode

Reduced

Anions are ___________ at the Anode

Oxidized

____________(Cathode) with more _________ electrode potential occurs first

Reduction; positive

____________(Anode) with more ___________ electrode potential occurs first

Oxidation; negative

Chapter 19 Electrochemistry Flashcards

(70 cards)