Oxidation-Reduction Worksheet



Oxidation-Reduction Study Guide Chemistry

Answer questions on this sheet Text: Chapters 20 and 21

I. Oxidation Numbers…pp. 641-643

1. In chemical reactions, elements on the left side of the periodic table tend to ____________

Electrons and those of the right side tend to ______________ electrons.

2. Define oxidation number._______________________________________________________

___________________________________________________________________________

3. a. What is the oxidation for a pure element? ___________________________________

b. What is the oxidation for oxygen in all compounds except peroxides? _______________

4. What does the algebraic sum of the oxidation #’s for all stoms equal in

a. Neutral compound _______________ b. Polyatomic ion __________________

5. Assign oxidation #’s to each atom in the following: Ex. CO2…C+4O2-2

a. H2O b. NO2 c. KMnO4 d. SO4

6. Give the oxidation #’s of nitrogen in each of the following compounds.

a. NO2 b. N2O5 c. N2O d. NO e. HNO3 f. Ca3N2

II. Redox reactions… pp. 635-640

The Facts:

OXIDATION REDUCTION

• Loss of electrons gain of electrons

• Increase in oxidation decrease in oxidation #

• Substance oxidized is the reducing agent substance reduced is the oxidizing agent

• e- is written on product side in half reaction e- is written on the reactant side in half reaction….Ex. Na ( Na+ + e- reaction. Ex. Cl + e- ( Cl-

REDOX REACTION: any chemical process in which elements undergo a change in oxidation #.

Remember!

L E O THE LION GOES G E R

O L X A L E

S E I I E D

E C D N C U

T A T C ( Memorize this, it will help!

R T R T

O I O I

N O N O

S N S N

1. Define: the following terms

a. oxidation ____________________________________________________________________

b. reduction ____________________________________________________________________

c. oxidizing agent ________________________________________________________________

d. reducing agent ________________________________________________________________

2. Are the following half reactions oxidation (ox.) or reduction (red)?

a. Cu+2 + 2e-2 ( Cu0 ___________________________________

b. Fe0 ( Fe+3 + 3e- ___________________________________

c. Mn+2 ( Mn+4 + 2e- ___________________________________

d. Mn+7 + 5e- ( Mn=2 ___________________________________

3. In the following reactions, label what is oxidized and what is reduced. ( Hint: first assign oxidation numbers to each element in reactants and products.)

a. 4Fe + 3O2 ( 2Fe2O3 ox.____________ red..___________

b. 3CuSO4 + 2Al ( Al2(SO4)3 + 3Cu ox ___________ red ___________

c. H2S + 2HNO3 ( H2SO4 + 2NO2 + H2O ox ____________ red_____________

III. BALANCING REDOX REACTIONS pp. 645-653

THE FACTS:

Mass, atoms and charge must be conserved.

Mass…must have the same # and type of atoms on both sides of the equation.

Charge..e- lost = e- gained

BALANCE: NO2- + I- ( NO(g) + I2 (s)

Step 1: Take the equation and split it into 2 “logical” half reactions.

a. NO2- ( NO b. I- ( I2

Step 2: Balance all elements by using coefficients EXCEPT hydrogen and oxygen.

a. NO2- ( NO b. 2 I- ( I2

Step 3: Balance the O’s by adding H2O’s where ever needed

a. NO2- ( NO + H2O b. 2 I- ( I2

Step 4: Balance H's by adding H+'s wherever needed.

a. 2H+ + NO2 --( NO + H2O Note, adding the 2 H+'s on the left took care of the H's.

b. 2I– --( I2 Again, no H's to worry about.

Step Five: Add electrons in order to balance the charge.

a. e– + 2H+ + NO2– --(NO + H2O b. 2I– --( I2 + 2e–

Step Six: Multiply the two equation by a set of numbers so that e lost equals e gained.

a. 2X (e– + 2H+ + NO2 --(NO + H2O) b. 2I– --( I2 + 2e–

Now add the two halves together since the electrons are equal.

2I– + 4H+ + 2NO2– --( 2NO + 2H2O + I2 BALANCED EQUATION

1. Balance the following

HCl(aq) + KMnO4(aq) ( H2O(l) + KCl(aq) + MnCl2(aq) + Cl2(g)

IV. Electrochemistry CHAPTER 21

Oxidation takes place at the anode (an ox)

• Reduction takes place at the cathode (car)

Electrochemical Cells

• Electrochemical Cells produce electrical current.

• Batteries are examples of Electrochemical Cells.

• Electrochemical Cells are spontaneous…delta G is negative.

• Oxidation takes place at the anode (an ox)

• Reduction takes place at the cathode (car)

• Anode is negative

• Cathode is positive

• Current flows anode to cathode.

Electrolytic Cells

• Electrolytic cells use electrical current to do work.

• Electrolysis and electroplating are examples of electrolytic Cells.

• Electrochemical Cells are nonspontaneous…delta G is positive.

• Oxidation takes place at the anode (an ox)

• Reduction takes place at the cathode (car)

• Anode is positive

• Cathode is negative

• Current flows anode to cathode.

Electrochemical/Galvanic Cell

[pic]

pp. 663-682

Finding Cell Potential

1. Find the two electrode metals on the Standard Reduction Chart. pg 667

2. The more positive is the cathode. Write down its value.

3. The more negative is the anode. Since oxidation takes place at the anode, the reaction is reversed and the sign of the anode is changed.

4. Add the two values to get the cell potential.

5. Electrochemical cells must have a positive potential

1. What is an electrochemical cell? Give an example.

2. Batteries are examples of ___________________________________ cells.

3. Electrochemical cells are examples of _________________________ (spontaneous, nonspontaneous) change.

4. A set of electrodes and electrolytes in which a spontaneous redox reaction is used to produce electrical energy is

called a _________________ cell.

5. Oxidation takes place at the ___________________________.

6. Reduction takes place at the __________________________.

7. In an electrochemical cell, the anode has a ______________ charge and the cathode has a ___________ charge.

8. Batteries are _______________ cells.

9. List four types of batteries. ______________ and _____________ and ____________ and ______________.

10. Find the potential in the cell shown above. ___________________________________

pp. 683-687

10. What is an electrolytic cell? Give an example.

11. Discuss the electrolysis of water. Include the equation for the reaction.

12. Discuss the process of electroplating.

13. Electrolytic cells are examples of _________________________ (spontaneous, nonspontaneous) change.

14. List two electrolytic processes. _______________________ and ___________________________

15. In an electrolytic cell, the anode has a ______________ charge and the cathode has a ___________ charge.

16. Draw an electrochemical cell and label the parts. P 685

17. Draw an electrolytic cell used for electroplating and label the parts. P. 687

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download