Transcript Regents Warm Up

Regents Warm Up
What is the total number of
electrons in a Mg2+ ion?
(1) 10
(3) 14
(2) 12
(4) 24
ELECTROCHEMISTRY
AIM:
What is an Electrolytic Cell?
Do Now:
What is a salt bridge?
Voltaic Cell Review
• What kind of Redox rxn
occurs in all VOLTAIC
Cells?
• What occurs in the left
half-cell?
• What is the electrode in
the right half-cell called?
• Where are electrons
generated?
Which statement is true about
oxidation and reduction in an
electrochemical cell?
1. Both occur at the anode.
2. Oxidation occurs at the anode
and reduction occurs at the
cathode.
3. Both occur at the cathode.
4. Oxidation occurs at the cathode
and reduction occurs at the
anode
Electrolytic Cell
• Electrolytic Cells:
Electrochemical Cells
used to FORCE
non-spontaneous redox
reactions to occur.
• They do NOT generate
electrical energy – they USE it!
• An electric current is applied to
the cell to make it run – this is
called ELECTROLYSIS
• Electrolytic Cells are similar
to Voltaic Cells
• They both have:
1. Oxidation occuring at the
Anode
2. Reduction occuring at the
Cathode
3. Electrons travel from the
Anode to the Cathode
Electrolytic Cells
• The difference is that
in electrolytic cells the
electrons are forced to
move from the anode
to the cathode
A voltaic cell differs from an
electrolytic cell in that in a
voltaic cell
1. energy is produced when
the reaction occurs
2. both oxidation and
reduction occur
3. energy is required for the
reaction to occur
4. neither oxidation nor
reduction occurs
Electrolytic Cell
• Main Uses Include:
1. Producing Substances
(Electrolysis)
2. Purifying Metals
3. Electroplating
Which process occurs at
the anode in an
electrochemical cell?
1. the loss of protons
2. the gain of protons
3. the loss of electrons
4. the gain of electrons
Practice
Where does oxidation occur in an
electrochemical cell?
Which statement is true for
any electrochemical cell?
1. at the cathode in both an electrolytic
cell and a voltaic cell
3. at the anode in both an electrolytic
cell and a voltaic cell
2. at the cathode in an electrolytic cell
and at the anode in a voltaic cell
4. at the anode in an electrolytic cell and
at the cathode in a voltaic cell
1. Oxidation occurs at the
anode, only.
2. Oxidation occurs at both
the anode and the cathode.
3. Reduction occurs at the
anode, only.
4. Reduction occurs at both
the anode and the cathode.
Short Answer Question
Aluminum is one of the most abundant metals in Earth's crust. The
aluminum compound found in bauxite ore is Al2O3. Over one
hundred years ago, it was difficult and expensive to isolate
aluminum from bauxite ore. In 1886, a brother and sister team,
Charles and Julia Hall, found that molten (melted) cryolite,
Na3AlF6, would dissolve bauxite ore. Electrolysis of the resulting
mixture caused the aluminum ions in the Al2O3 to be reduced to
molten aluminum metal. This less expensive process is known as
the Hall process.
Explain, in terms of electrical energy, how the operation of a
voltaic cell differs from the operation of an electrolytic cell used
in the Hall process. Include both the voltaic cell and the
electrolytic cell in your answer.
ANSWER
• A voltaic cell produces
electrical energy by
using a spontaneous
redox reaction. An
electrolytic cell uses
electrical energy to drive
a redox reaction that is
not spontaneous.
Short Answer Question 2
• Electroplating is an electrolytic
process used to coat metal
objects with a more expensive
and less reactive metal. The
accompanying diagram shows
an electroplating cell that
includes a battery connected to
a silver bar and a metal spoon.
The bar and spoon are
submerged in AgNO3(aq).
Explain the purpose of the
battery in this cell.
Answer Short Answer 2
• The electrolysis reaction
is not a spontaneous
reaction. Therefore, an
external source of
energy (the battery) is
needed to drive the
reaction.
Batteries
• There are 3 Types of
Batteries
1. Dry Cell: do not contain
a liquid, instead has a
paste
• Inner case is the anode
• Carbon rod+paste work as
cathode
Batteries
1a) Primary Dry Cell:
Uses a redox rxn that is
NOT easily reversible
Batteries
1b) Secondary Dry Cell:
• Uses a redox reaction
that is reversible
• These are rechargable
batteries
Batteries
2) Lead Storage
• Anode is Pb, Cathode
is PbO2
• Typically uses H2SO4
• Operate well at
extreme temps
Batteries
3. Lithium Batteries
• Li is easily oxidized
and generates more
voltage
• Last longer then most
other batteries