Electrochemistry

Redox Reaction

Reactions in which electrons are transferred from one reagent to another

Oxidation State

The hypothetical change of an atom if all of its bonds were fully ionic

Oxidation is _______ of electrons

Loss

Reduction is _______ of electrons

Gains

Aqueous Reactions

Are chemicals reactions that take place in water

Molecular Equation

Gives the complete neutral formulas of each compound in the reaction as if they existed as molecules

Complete Ionic Equation

• shows the reactants and products as individual ions

• Breaks down substance present in the solution

What form of substances do not separate into a Complete Ionic Equation?

• Solids

• Liquids

• Gases

Spectator Ions

Do not participate in the chemical reaction

Net Ionic Equation

• spectator ions are omitted

• Shows only the species that actually participate in the chemical reaction

What are the two methods for balancing redox equations?

• Acidic Solutions

• Basic Solutions

Name two things that can constitute electrical current?

• electrons flowing through a wire

• Ions flowing through a solution

Voltaic Cell

Is an electrochemical cell that produces electric current from a spontaneous chemical reaction

Half-Cell

Half of an electrochemical cell where either oxidation or reduction occurs

Anode

• electrode where oxidation occurs

• (-) Negative

electrons flow _____ the anode

away from

When describing a voltaic cell, the anode is given a _____ sign

Negative

Cathode

• Electrode where reduction occurs

• (+) Positive

Electrons flow ______ the cathode

Toward

when describing a voltaic cell, the cathode is given a ____ sign

Positive

Salt bridge

Is a tube filled with a strong electrolyte that connects the two half cells

Amperes

Electrical current is measured in units

What is the charge of an electron?

1.602×10^-19c

Potential Difference

Electrical current is driven by a difference in potential energy

Line Notation

Compact notation to describe voltaic cells

What is the relationship between standard free energy change (G) and standard cell potential (Ecell)

G=-nFEcell

How is the standard cell potential (Ecell) calculated from standard electrode potentials?

E*cell=E*cathode-E*anode

In the electrolysis of molten salt mixtures, which cation is reduced first?

The cation with the least negative electrode potential

What equation is used to calculate cell potential under non-standard conditions?

Nernst Equation

What is electrolysis?

The process where an electric current drives a non-spontaneous redox reaction

What is the oxidation state of oxygen in most compounds according to the rules for assigning oxidation states?

-2

In a voltaic cell, at which electrode does oxidation occur?

Anode

What is the relationship between standard cell potential ( Ecell) and the spontaneity of a redox reaction?

A positive Ecell indicates a spontaneous reaction

What is the purpose of a salt bridge in a voltaic cell?

To neutralize charge accumulation in the half-cells

What is the definition of oxidation in redox reactions?

Loss of electrons

What are spectator ions in a redox reaction?

Ions that do not participate in the chemical reaction

What is the relationship between cell potential (Ecell) and the equilibrium constant (K)?

E*cell=(0.0592/n)log(K)

What is the oxidation state of a free element?

0

What is Faraday’s constant used for in electrochemistry?

to represent the charge in coulombs of 1 mol of electrons

In a balanced chemical equation for a redox reaction, what must be equal on both sides?

Both the number of atoms and charges

In the electrolysis of aqueous salt solutions, what determines which reaction take place at each electrode?

The reaction that occurs more easily (based on electrode potentials)

What is the charge of the cathode in a voltaic cell?

Positive

What is the alternative name for voltaic cells?

Galvanic cells

What happens in a concentration cell when the concentrations of the solutions are different?

The reaction shifts according to Le Chatelier’s principle, resulting in a cell potential