Unit 16: Redox Reactions

Oxidation Numbers

100

What is the oxidation number of unbonded elements?

0

200

In a compound or polyatomic ion, how do you determine what element will be negative?

The more electronegative element will be the negative element (has the electrons around it more)

300

What is the oxidation number of Sulfur in the following...

Sulfur dioxide -- SO₂

The sulfate ion -- SO₄^2-

The sulfite ion -- SO₃^2-

+4

+6

+4

400

What is the oxidation number of each element  in sodium dichromate (NaCr₂O₇) and and zinc chromate (ZnCrO₄)

Na = 1+,    Cr = 6+,     O=2-

Zn = 2+,    Cr = 6+,     O=2-

Categorizing Chemical Species as Oxidized, Reduced, Oxidizing Agent, or Reducing Agent

100

The oxidizing agent in the following: 2Li + S ---> Li2S

What is Sulfur?

200

The chemical reduced in the following: 

4Fe + 3O₂ ---> 2 Fe₂O₃

Oxygen

300

The reducing agent in the following: 

Mg + 2HCl ---> MgCl₂ + H₂

Magnesium

400

The oxidized compound in the following: 

KMnO₄ + HCl ---> MnCl₂ + Cl₂ + H₂O + KCl

Chlorine

500

Identify the oxidizing agent, reducing agent, reduced compound, & oxidized compound in the following: K₂Cr₂O₇ + SnCl₂ + HCl --> CrCl₃ + SnCl₄ + KCl + H₂O

What is Chromium (Reduced-Oxidation Agent) & 

Tin (Oxidized-Reducing Agent)

Half-Reactions

100

What are the two 1/2 reactions for this reaction?

2Sr + O₂ → 2SrO  

Sr --> Sr²⁺ + 2 e^-

2e ^- + O₂ -->  O^2-

200

Identify the 1/2 reactions

3 Mg + N₂→ Mg₃N₂ 

3 Mg --> 3 Mg²⁺ + 6 e^-

6 e^- + N₂ --> 2 N^3-

 

400

The balanced oxidation half-reaction of the following: H2C2O4 + KMnO4 ---> CO2 + K2O + Mn2O3 + H2O

What is C2O4^2- ---> 2CO2 + 2e- ?

500

What are the half reactions for the following reaction (you don't need to cancel the electrons).

KMnO₄ + KNO₂ + H₂SO₄ --> MnSO₄ + H₂O + KNO₃ + K₂SO₄

(oxidation) NO₂^1- ---> NO₃^1- + 2e- + 2H⁺  

(reduction) MnO₄^1- + 5e^- + 8H⁺ ---> Mn^2+ + 4H2O ?

Balancing Redox Reactions

100

Balance the following redox reaction: H+ + SO3^2- + MnO4^- ---> SO4^2- + Mn^2+ + H2O

What is 6H+ + 5SO3^2- + 2MnO4^- ---> 5SO4^2- + 2Mn^2+ + 3H2O ?

200

Balance the following redox reaction: H+ + Br- + Cr2O7^2- ---> Br2 + Cr^3+ + H2O

What is 14H+ + 6Br- + Cr2O7^2- ---> 3Br2 + 2Cr^3+ + 7H2O ?

300

Balance the following redox reaction: Fe + V2O3 ---> Fe2O3 + VO

What is 2Fe + 3V2O3 ---> Fe2O3 + 6VO ?

400

(Daily Double) Balance the following redox reaction: H2C2O4 + KMnO4 ---> CO2 + K2O + Mn2O3 + H2O

What is 4H2C2O4 + 2KMnO4 ---> 8CO2 + K2O + Mn2O3 + 4H2O ?

500

Balance the following redox reaction: KMnO4 + KNO2 + H2SO4 ---> MnSO4 + H2O + KNO3 + K2SO4

What is 2KMnO4 + 5KNO2 + 3H2SO4 ---> 2MnSO4 + 3H2O + 5KNO3 + K2SO4 ?

Completed Half-Reactions

100

Determine the two redox half-reactions of the following (electrons must cancel): Mg + HCl ---> MgCl₂ + H₂

Mg ---> Mg²+ + 2e^-

2 H⁺ + 2 e^- --> H₂

200

The balanced reduction half-reaction of the following: 

(electrons must cancel)

Fe + V₂O₃ ---> Fe₂O₃ + VO

2 V³⁺ + 2e^- --> V²⁺ 

Fe --> Fe³⁺ + 3 e^-