1. Chapter 21: Electrochemistry
Table of Contents
Chapter 21: Electrochemistry
21.1 – Voltaic Cells

2. Review Zn + NiSO4 → Ni + ZnSO4
Basic Assessment Questions
Review
Identify what is oxidized and what is reduced.
Zn + NiSO4 → Ni + ZnSO4
Ox: Zn
Red: Ni2+
Define
Redox reactions
Oxidation
Reduction
Half-reactions

3. Electrochemistry is using chemistry to create electricity
Electrochemistry: Basic Concepts
Electrochemistry is using chemistry to create electricity
Electrical current: The flow of electrons in a certain direction
Redox reactions can produce an electrical current.
This is what occurs in a battery—one form of an electrochemical cell

4. Electrochemical cell: a device that uses
Electrochemistry: Basic Concepts
Definitions
Electrochemical cell: a device that uses
redox reactions to create electricity OR
electric energy to cause chemical reactions
Voltaic or galvanic cell:
creates electricity by a spontaneous redox reaction.
a type of electrochemical cell.

5. Balanced: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
Total ionic:
Zn(s) + Cu2+(aq) + SO42-(aq) → Zn2+(aq) + SO42-(aq) + Cu(s)
Net ionic: Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) ox
red
Half Reactions:
Zn(s) → Zn2+(aq) + 2e-
Half Reactions:
Zn(s) → Zn2+(aq) + 2e- Cu2+(aq) + 2e-→ Cu(s)

6. Electrochemical Cell
Zinc strip
Copper strip
Cannot transfer e-
SO42-
SO42-
CuSO4(aq)
ZnSO4(aq)
Zn2+
Cu2+
Zn(s) → Zn2+(aq) + 2e-
Cu2+(aq) + 2e-→ Cu(s)

7. Electrochemical Cell
Allows e- transfer
Copper wire
(+) charge builds up in one solution, (-) charge builds up in the other

8. Allows ions to pass from one side to the other
Electrochemical Cell
Allows ions to pass from one side to the other
Ions pass through plugs in the bridge, but solutions do not mix
Salt bridge
KCl
Circles = plug, algae gel

9. Electrochemical Cell Zn → Zn2+ + 2e- Cu2+ + 2e- → Cu e- flow K+ Cl-
e- e-
Cl- K+
e- e- Zn
Cl- K+ Cu
Circles = plug, algae gel
Zn2+
Cu2+
Zn → Zn2+ + 2e-
Cu2+ + 2e- → Cu

10. What is this called? What does it do?
Why can redox reactions create electricity?
e- flow
KCl Zn Cu
Circles = plug, algae gel
1M Zn2+
1M Cu2+
Zn → Zn2+ + 2e-
Cu2+ + 2e- → Cu

11. Voltaic/Galvanic Cell
e- flow
KCl
electrodes
electrodes
half-cells Zn Cu
Circles = plug, algae gel
Zn2+
Cu2+
electrolytes

12. Electrolytes: a solution of ions
Electrochemistry: Basic Concepts
Definitions
Half-cells: Where oxidation and reduction reactions separately take place (2 parts)
Electrode: an object in the half-cell that conducts electrons to or from another substance – immersed in electrolytes
Electrolytes: a solution of ions

13. Voltaic/Galvanic Cell Voltaic Cell
e- flow
KCl Zn Cu
oxidation
ANODE
Circles = plug, algae gel
reduction
CATHODE
1M Zn2+
1M Cu2+
Zn → Zn2+ + 2e-
Cu2+ + 2e- → Cu

14. Anode: The electrode where oxidation takes place
Electrochemistry: Basic Concepts
Definitions
Anode: The electrode where oxidation takes place
Cathode: The electrode where reduction takes place
Electrons always flow from the anode to the cathode

15. Let’s see it

16. On the following slides, identify… Salt bridge What is oxidized
Electrochemistry: Basic Concepts
Practice
On the following slides, identify…
Salt bridge
What is oxidized
What is reduced
Cathode
Anode
Direction of e- flow through wire

17. Voltaic/Galvanic Cell
oxidized
reduced

18. Voltaic/Galvanic Cell
e- flow

19. Voltaic/Galvanic Cell
Salt bridge