unit 5 - electrochemistry

What is electrochemistry?

• electrochemistry is the study of chemical processes that cause electrons to move

• it involves chemical reactions that either absorb or release energy in the form of electricity

What is oxidation reaction vs reduction reaction? What is a redox reaction?

• oxidation reaction

  • results in the loss of electrons and increase in oxidation number

• reduction reaction

  • results in the gain of electrons and a decrease in oxidation number

• Redox reaction

  • the net reaction involving both the reduction and oxidation reaction

What is an electrochemical cell?

• any device that converts chemical energy to electrical energy or electrical energy to chemical energy

What are the three components needed to make up an electrochemical reaction?

• There must be a solution where redox reactions can occur

• A conductor must exist for electrons to be transferred

• Ions must also be able to move through some form of salt bridge that helps with ion migration

What is the oxidation number of an atom? What do we assume the more electronegative atom bond does?

• it is the charge the atom appears to have in a compound

• we assume the more electronegative atom in a bond always gains electrons entirely, even if the bond is covalent

oxidation number:

C

• 0

oxidation number:

CO

• C = +2

• O = -2

oxidation number:

CO₂

• C = +4

• O = -2

oxidation number:

CO₃^2-

• O = -2

• C = +4

oxidation number:

ClO₃^-

• O = -2

• Cl = +5

oxidation number:

N₂O

• O = -2

• N = +1

oxidation number:

NO

• O = -2

• N = +2

oxidation number:

N₂O₃

• O = -2

• N = +3

oxidation number:

NO₂

• O = -2

• N = +4

oxidation number:

CuNO₃

oxidation number:

CrO₄^2-

• O = -2

• Cr = +6

oxidation number:

OF₂

• F = -1

• O = +2

oxidation number:

Na₂O₂

• Na = +1 (group 1 = +1)

• O = -1 (peroxide)

oxidation number:

Fe(CN)₂

oxidation number:

H₂S

• H = +1

• S = -2

oxidation number:

Na₂SO₄

• O = -2

• Na = +1

• S = +6

oxidation number:

SO₂

• O = -2

• S = +4

oxidation number:

Na₂S₄O₆

• O = -2

• Na = +1

• S = -2.5

oxidation number:

SO

• S = +2

• O = -2

oxidation number:

SO₂

oxidation number:

SO₃

oxidation number:

H₃PO₂

oxidation number:

H₃PO₃

oxidation number:

H₃PO₄

oxidation number:

H₄P₂O₇

oxidation number:

H₅P₃O₁₀

oxidation number:

Cs₂O

oxidation number:

ClF₃

oxidation number:

MoO₄^2-

oxidation number:

PtCl₆^2-

oxidation number:

H₃AsO₃

oxidation number:

MnO₄^-

oxidation number:

CaI₂

oxidation number:

PtCl₄^2-

oxidation number:

SnF₂

oxidation number:

TiO₂

oxidation number:

Al₂O₃

What is oxidizing agent vs reducing agent

• Oxidizing agent: Substance that oxidizes another substance (opposite of reduced)

• Reducing agent: Substance that reduces another substance (opposite of oxidized)

Write the:

• substance oxidized

• substance reduced

• oxidizing agent

• reducing agent

• oxidation half reaction

• reduction half reaction

Na_(s) + H₂O_(l) →NaOH_(aq) + H_2(g)

Write the:

• substance oxidized

• substance reduced

• oxidizing agent

• reducing agent

• oxidation reaction

• reduction reaction

Cl_2(g) + NaBr_(aq) → Br_2(g) + NaCl_(aq)

Write the:

• substance oxidized

• substance reduced

• oxidizing agent

• reducing agent

• oxidation reaction

• reduction reaction

Fe₂O₃ + H₂ → H₂O + Fe

Write the:

• substance oxidized

• substance reduced

• oxidizing agent

• reducing agent

• oxidation reaction

• reduction reaction

H₂ + O₂ → H₂O

Write the:

• substance oxidized

• substance reduced

• oxidizing agent

• reducing agent

• oxidation reaction

• reduction reaction

FeCl₂ + Cl₂ →FeCl₃

Balance the redox reaction:

CuO + NH₃ →Cu + N₂

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Balance the redox reaction:

HNO₃ + HI →NO + I₂

Balance the Redox reaction

Cu + HNO₃ →Cu(NO₃)₂ + NO₂

Balance the Redox reaction:

Cr₂O₇^2- + Cl^- → Cr³⁺ + Cl₂ (in basic solution)

Balance the redox reaction:

CrO₄^2- + SO₃^2- → Cr³⁺ + SO₄^2- (basic)

Balance the redox reaction:

MnO₄^- + C₂O₄^2- → Mn²⁺ + CO₂ (acid)

Balance the redox reaction:

Cl₂ + IO₃^- → IO₄^- + Cl^- (basic)

Balance the redox reaction:

NO₃^- + As₂S₅ → H₃AsO₄ + S + NO (acid)

Balance the redox reaction:

Al + MnO₄^- → MnO₂ + Al(OH)₄^- (basic MnO₂)

Balance the redox reaction:

CH₃OH + Cr₂O₇^2- → CH₂O + Cr³⁺ (acidic Cr₂O₇^2-)

Balance the redox reaction:

NO₂^- + Al → NH₃ + AlO₂^- (basic)

Balance the redox reaction:

CN^- + MnO₄^- → CNO^- + MnO₂

Balance

Recall the grade 11 activity series

17

• Li

• K

• Ba

• Ca

• Na

• Mg

• Al

• Zn

• Fe

• Ni

• Sn

• Pb

• H

• Cu

• Ag

• Hg

• Au

Write the reaction, the oxidation half reaction, the reduction half reaction and the net ionic equation

Which is better at being reduced (which is the better oxidizing agent) Cu²⁺ or Fe²⁺?

Which one is oxidation and which is reduction

and which one is anode and which one is cathode

and do cell notation and label the diagram for red and ox and cathode and anode

and do cell notation and label the diagram for red and ox and cathode and anode

Draw an electrochemical cell for copper(II) nitrate and zinc nitrate

Label everything properly including reduction and oxidation and anode and cathode

Write down the half equations and write the net ionic equation

Do cell notation

Calculate the theoretical voltages

Draw an electrochemical cell for zinc nitrate and aluminum sulfate

Label everything properly including reduction and oxidation and anode and cathode

Write down the half equations and write the net ionic equation

Do cell notation

Calculate the theoretical voltages