Introduction to Electrochemistry (Part 1)
Summary
TLDRThis lecture delves into the fundamentals of electrochemistry, exploring electrochemical cells where oxidation-reduction reactions occur to produce or utilize electric current. It covers cell potential, voltage, and cell notation, essential for understanding potentiometry and redox processes. The instructor explains the difference between galvanic and electrolytic cells, the significance of electrodes, and the role of the salt bridge in maintaining charge neutrality. The lecture also introduces Nernst equation, Ohm's law, and the concept of standard reduction potential, providing a foundation for further study in electrochemistry.
Takeaways
- đ Electrochemistry is the study of chemical reactions that produce or require an electric current, converting chemical energy into electrical energy within an electrochemical cell.
- đŹ The main components of an electrochemical cell include electrodes, a voltmeter, a salt bridge, and beakers containing solutions where oxidation and reduction occur.
- đ In electrochemical notation, the anode is on the left and is where oxidation occurs, while the cathode is on the right and is where reduction occurs.
- đ« A voltaic or galvanic cell is a spontaneous redox reaction that generates electrical current, whereas an electrolytic cell requires an external electrical energy source for non-spontaneous reactions.
- đ The salt bridge's purpose is to maintain electrical neutrality in the solutions, allowing ions to move freely to balance the charge.
- đ Ohm's Law is used to measure electric current in amperes, and the Nernst Equation relates the cell potential to the standard reduction potential, temperature, and concentrations of the species involved.
- ⥠The standard reduction potential values are crucial for determining the oxidizing and reducing powers of elements in a reaction.
- đĄïž The Nernst Equation is temperature-dependent, with standard reduction potentials measured at 25 degrees Celsius.
- đ The overall cell potential is calculated by subtracting the standard reduction potential of the anode from that of the cathode in a galvanic cell.
- đ Line notation is used to write the reactions in electrochemical cells, indicating changes in state, concentrations, and the junction between half-cells.
- đ The cell potential and the spontaneity of a reaction can be determined by comparing the standard reduction potentials of the elements involved.
Q & A
What is electrochemistry?
-Electrochemistry is the study of chemical reactions that produce or require an electric current, involving the conversion of chemical energy into electrical energy in an electrochemical cell.
What are the two types of electrodes in an electrochemical cell?
-The two types of electrodes in an electrochemical cell are the anode and the cathode. The anode is where oxidation occurs and is connected to the positive end of a battery, while the cathode is where reduction occurs and is connected to the negative end.
What is the difference between a galvanic cell and an electrolytic cell?
-A galvanic cell, also known as a voltaic cell, is a type of electrochemical cell in which a spontaneous redox reaction occurs to produce an electric current. An electrolytic cell, on the other hand, is a non-spontaneous redox reaction where electrical energy is applied to drive a chemical reaction, a process known as electrolysis.
What is the role of a salt bridge in an electrochemical cell?
-The salt bridge in an electrochemical cell serves to maintain electrical neutrality by allowing ions to flow between the two half-cells, thus facilitating the movement of electrons and the completion of the electrical circuit.
What is the significance of the standard reduction potential?
-The standard reduction potential is a measure of the tendency of a chemical species to acquire electrons and is used to predict the spontaneity of redox reactions and to calculate the cell potential of electrochemical cells.
How is the voltage of an electrochemical cell determined?
-The voltage of an electrochemical cell is determined by the difference in standard reduction potentials of the two half-reactions involved, with the cathode typically having a higher potential than the anode.
What is Ohm's law, and how is it used in electrochemistry?
-Ohm's law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. In electrochemistry, it can be used to calculate the electric current in an electrochemical cell given the voltage and resistance.
What is the Nernst equation, and why is it important in electrochemistry?
-The Nernst equation is used to relate the reduction potential of an electrochemical reaction to the standard electrode potential, temperature, and the concentrations of the chemical species involved. It is important for predicting the cell potential under non-standard conditions and for understanding the behavior of electrochemical cells.
How do you write the line notation for an electrochemical cell?
-The line notation for an electrochemical cell is written by listing the components of the cell from left to right, starting with the anode on the left and ending with the cathode on the right. It includes the electrodes, the solutions they are immersed in, and the salt bridge, with states of matter and concentrations indicated as necessary.
What does the term 'oxidizing power' refer to in the context of electrochemistry?
-Oxidizing power refers to the ability of a substance to oxidize other substances, i.e., to accept electrons from them. In electrochemistry, substances with higher standard reduction potentials have greater oxidizing power.
Outlines
đŹ Introduction to Electrochemistry
The lecture begins with an introduction to electrochemistry, a field that studies chemical reactions involving electric current. The PowerPoint is credited to Dr. Joel, and the lecture covers the basics of electrochemical cells, including oxidation and reduction processes, voltage, and cell notation. The instructor emphasizes the relevance of these concepts to analytical chemistry, potentiometry, and redox reactions. The session is designed to provide foundational knowledge for students studying these topics.
đ Electrode Processes and Cell Types
This section delves into the specifics of electrochemical cells, focusing on the roles of anodes and cathodes in oxidation and reduction reactions. The anode facilitates oxidation, losing electrons, while the cathode promotes reduction, gaining electrons. The instructor explains the difference between galvanic (voltaic) cells, which produce electrical energy through spontaneous redox reactions, and electrolytic cells, which require electrical energy to drive non-spontaneous reactions. The lecture also touches on the concept of voltage and how it's generated in these cells.
đ Exploring Electrode Reactions and Ohm's Law
The script discusses the movement of electrons from the anode to the cathode, generating an electric current that can be measured using a voltmeter. Ohm's Law is introduced as a fundamental principle for calculating electric current. The instructor also explains the relationship between the number of electrons transferred, the Faraday's constant, and the electric potential developed in an electrochemical cell. The section includes an example of a cell that does not produce an electric current due to the formation of silver chloride on the electrode.
đ Standard Reduction Potential and Electrode Notation
The lecture continues with an exploration of standard reduction potential, which is used to determine the oxidizing and reducing powers of elements in a reaction. The instructor explains how to write half-cell reactions and how to combine them to form the overall cell reaction. The concept of line notation for electrochemical cells is introduced, including the representation of states, concentrations, and the use of single and double vertical lines to indicate changes and junctions between half-cells.
đ Writing Line Notations and Understanding Cell Reactions
This part of the lecture provides a practical guide to writing line notations for electrochemical cells, including how to represent electrodes, solutions, and concentrations. The instructor uses an example of a galvanic cell setup to illustrate the process of writing line notations, emphasizing the placement of anode and cathode and the significance of the salt bridge in maintaining electrical neutrality.
đ Nernst Equation and Reaction Quotient
The script introduces the Nernst equation, which is used to calculate the electric potential of a cell reaction based on the standard reduction potential, temperature, and concentration of the species involved. The instructor explains the relationship between the Nernst equation and the Gibbs free energy, highlighting the importance of the reaction quotient in determining the cell potential. The section concludes with an example of how to derive and apply the Nernst equation to a specific electrochemical cell.
đ Conclusion and Anticipation of Problem Solving
The lecture concludes with a brief overview of the topics covered and a teaser for the next lecture, which will focus on problem-solving in electrochemistry. The instructor summarizes the key points discussed, including the Nernst equation and its application, and encourages students to review the material in preparation for the next session. The closing remarks aim to reinforce the importance of understanding the fundamental concepts of electrochemistry for future studies.
Mindmap
Keywords
đĄElectrochemistry
đĄElectrodes
đĄGalvanic Cell
đĄElectrolytic Cell
đĄVoltage and Cell Potential
đĄSalt Bridge
đĄOhm's Law
đĄStandard Reduction Potential
đĄNernst Equation
đĄReduction-Oxidation (Redox) Reaction
đĄLine Notation
Highlights
Introduction to electrochemistry as the study of reactions that produce or require electric current.
Explanation of the conversion of chemical energy into electrical energy within an electrochemical cell.
Identification of electrodes in electrochemical cells, including the anode and cathode and their respective roles.
Discussion on the difference between oxidation and reduction in the context of an electrochemical cell.
Introduction of voltaic or galvanic cells where spontaneous redox reactions produce electrical current.
Description of electrolytic cells and the process of applying electrical energy to drive non-spontaneous redox reactions.
Explanation of voltage and cell potential in electrochemical cells, including their positive and negative values.
Overview of the components of a typical galvanic cell setup, including electrodes, a voltmeter, and a salt bridge.
Role of the salt bridge in maintaining electrical neutrality and allowing ions to move freely.
Explanation of Ohm's law and its application in measuring electric current in electrochemical cells.
Introduction to the Nernst equation and its significance in determining the electric potential of electrochemical reactions.
Discussion on the standard reduction potential and its importance in comparing the oxidizing power of different reactions.
Explanation of cell notation, including single and double vertical lines, and their significance in electrochemical cells.
Demonstration of writing line notation for a galvanic cell, including the representation of half-cell reactions.
Application of the Nernst equation to calculate the cell potential based on the concentration of dissolved ions.
Discussion on the relationship between standard reduction potential and the spontaneity of electrochemical reactions.
Conclusion of the lecture with a summary of the key concepts and an introduction to the next lecture's focus on problem-solving.
Transcripts
hello class this is our lecture for our
electro
chemistry this this powerpoint by the
way was
made by my advisor dr joel so basically
it's not
my design in this lecture we will
discuss the overview of the
electrochemistry
the electrochemical cells where the
oxidation reduction will happen
we will talk about the voltage and cell
potential
and some sort of cell notation so this
is basically
topic for your analytical chemistry this
is the
basic concepts for the potentiometry by
which indiana manager discussed guys
so don't worry so stay there and basic
or potentiometry which is also
a relevant topic for our redox station
so let's start our topic for one day
okay let's
start so the overview and so what is
electro and streets the study of green
dots reaction
that produce or require an electric
current so it's either a co-produced
sha or a required electric current so
that
the chemical reaction will occur it is
the conversion
chemical energy in to
electrical energy that is carried out
in an electrochemical cell okay
so what are the terms elaborating
equally
we have the electrodes the electrodes
are located in our electro and calcium
cell these are the electrodes
okay this is the atode which is always
located on the right of our
electrochemical cell and this is the
anode which is located on the left side
of our
contact cell when you view it at this
perspective
and so as we cut out our
reduction of cures and anode our
sedation
i saw the anode guys anode
is where oxidation occurs cached in
there
and ions attracted to it in the
electrolytic cell connected to the
positive end of battery in
an electrolytic cell and losses losing
sweet
in electrolytic cells whereas the
cathode guys electrodes
were production of ears so parking
red cap red means reduction cut in
scattered production cathode
where reduction cures red cap okay
ions attracted to it in terms of electro
in terms of electrolytic cell connected
to the negative end of battery in
electric
cell gains with an electrolytic cell so
i am going to current
electro plating
and the the absorption of the
metal to its surface
so there are two types of electrolyte
cells we have voltaic cell or
galvanic cell and electrolytic cell so
the galvanic cell
is where spontaneous redox redox
reaction
takes place at two units to produce
non-electrical current
when the action takes place so it is a
spontaneous reaction
while electrolytic cells are
non-spontaneous
redox reaction so paramount procedure
chemical reaction veto
how to apply electrical energy which is
a process term
called electrolysis
voltage generates a electric potential
of capacity
with a positive value while electrolytic
cell
generates a negative value
current to produce a chemical reaction
in the electrolytic cell
so these are the typical setup of our
galvanic cell
when it's a given excel this is here and
so you would notice guys the chemical
reaction takes place it is comprised of
electrodes
a voltmeter salt bridge and these
two beakers or container which is
containing
our solutions where the other one is
reduced
and the other is oxidized okay so
when the reaction takes place and the
salt reached the purpose of the salt
bridge guys
is to maintain the electron neutrality
of the solution so that ions can float
easily whereas the the negatively
charged
or the the an ion attracted to the
oxidation appears this anode here
this anode this solution this cardio
will oxidize to produce an electron so
therefore
new is study resolved loses sweep in an
electrolytic reaction or galvanic
reaction
when product action occurs now this
electron still hit the notion of the
trouble
guys but rather the electron will travel
here
from anode to cathode to produce an
electric current and the voltmeter will
be responsible to measure
the uh in terms of voltage okay
so in my array while the reaction the
reduction reaction here will occur
the silver nitrate will decompose into
silver ion
and silver and nitrate ion and magna
reduction and magnetic deposits
silver electrodes
right so
[Music]
later on to this topic now let's see
this one here
why won't this cell work but can you
never work
why does not produce an electric current
we have this deposited silver chloride
in the electrode here while the carbon
will be dissolved
and oxidation reduction to form
a hydrochloride where is the chloride
smoking solution
to form with cadmium chloride
and immersed in a cadmium chloride
solution and by the way guys uh clarify
column
the only solution present here is only
cadmium chloride
and silver nitrate solution unlikely
silver electrode and canyon electrode so
electric current will produce so this
cell will work okay so
backbone for flow and electrons so hey
it's discussed earlier
i am we can
measure or determine the electric
current in
amperes when we use this formula what's
this
it's ohm's law and then when we impose
the gives free energy
generate and formula is negative
n which is the number of electron modes
the
f which is the faraday's constant and e
the potential or the electric potential
of
our reaction that is produced in
the electrochemical reaction here in the
cell by which
around them and our policies later on to
stop it
so says this this is our interest
at the voltaic cells this sun is
electrochemical cells that use an
oxidation reduction reaction
to generate an electric current
so it is a spontaneous reaction which is
the first type of our electrochemical
cell the voltaic cell or galvanic cell
this is the typical setup of our voltaic
cell now modulus you may encounter
senior
potentiometry and we have the excuse me
the reference electrode
and the metal electrode and there are
actually four types of electrode now
uh we will not go in depth to that same
size potentiometer
and we will just put this basic here
this is that we can set up
the reduction will occurs to cathode in
the anode blockers
oxidation at the anode so therefore
here so this is the stick when the
abroad reaction for the one
zinc oxidized the hydrogen is reduced
the overall action for the reaction here
is this
again so we can only measure the
electric potential reaction so actually
the half reactions are dependent on
something
half cell reaction error all right
so the inner part of the cell is the sum
of the
standard reduction potential the two
half cell
yeah we'll take cell so that is you know
previously is fully described with the
following innovation
we have the salt bridge the electrodes
used
and so and so forth
and here this is typical setup again of
our
electrochemical cell we have the silver
electrode and dating ohm
and alligator standard halogen with a
quantity and one barometric pressure of
hydrogen
sonar generation 0.53
volts and any concentration so this is
the
i don't know so here this is the quan
guys
we will use another equation the
formula for the nurse equation is given
by this equation
but we will focus on literally that
comprised of standard reduction
potential
the electric potential the standard
potential
reduction potential and this expression
okay so little something
about this part here will depend
on the value of the half cell reaction
their constant value is this
at all we have lithium which is uh
easily reduced which has a value of
negative three point four volts
and so on and so forth and then come up
happens nino
let's compare the reaction here ayan
as the the
standard reduction potential increases
their oxidizing power also increases
oxidizing power in the lab by which in
turn we will go on to this
connected vitals
[Music]
reaction here in the previous
lecture we talked about the reduction of
cover which is absorbed
on this zinc strip on the surface of the
sink street
what is pallete will the sink
reduce and absorbed in the copper strip
so the answer is no so why is that
surviving that's the reaction reversible
sir
you know the position
if we compare the standard deduction
potential
of the zinc and copper
masmata asymbalinal copper
by which in turn yung copper
has the capability to oxidize
the zinc
it's a sink and then the semi-copper but
the sink
is not capable to oxidize the copper
because copper has a higher oxidizing
power
than zinc
literature about that and usually
chemistry box okay
so let's back to our topic
notation
[Music]
so how do we do that okay i'm just uh
single vertical line indicates
change in state or face you know the
half cell directions are listed before
the products activities of solutions are
written in parenthesis
and after the simultaneous molecule and
the double vertical line
indicates a junction between half cells
the line notation for the anode
oxidation is always is written before
the line notation
for the cathode so basically anode
some examples guys here okay
since the action is not provided here
i'm going to do something
painting here and
here so ion this is the typical reaction
here
and so we have the cathode the anode is
always written on the right
and the atoms always retain on uh on the
left the anode is always sitting on the
left
the cathode is retained on the right so
nothing but the difference
this is the line notation suppose that
we have the
suppose that we have this set up this
two beaker here
containing zinc i think
then we have the salt bridge containing
beaker i am
like salt bridge here and then we have
this electrode
here please and then a voltmeter
and then here another electrode here
so ah
[Music]
so this is the copper electrode in this
one here is the
zinc electrode and this one here
contains the copper solution
this one here is the dissolution
this is the typical setup of it
is
and this one here is
and then the parentheses indicates this
is separately an
concentration and a result no solution
or a
solution okay here's the solution and
this one here i am solution again
this one here is the another electrode
of the cathode
or prada this one here acts
as a salt
bridge
so how do we write the line notation
of this galvanic cell okay
we have the cadmium electrode here
and then ayan the bamboo small is a left
then we have dissolved the cadmium
nitrate
cadmium nitrate here which is also
contains a
cadmium and penelope
and then sha eye melon concentration now
let's see
this one this also a 0.1 molar this one
here is 0.2 molar solution
0.1 molar here and then the salt bridge
for the nice salt bridge and then the
silver nitrate solution
and silver nitrate
or pedro not elegant silver ion
so parenthesis what's the concentration
0.2 molar
and then drag it again singapore we have
the electrode
silver yeah so that's how you write
the line notation for this galvanic set
so line notation here so activities
at the junction yeah the location for
the annual sleeping before the land
saya the junction between houses and
junctions
but there are no actually not products
so so yeah now we're done
with the written with the line notations
the electrochemical cells in standard
reduction potential
combine combining anatomy given details
we have the concentration we have the
electrodes
the species present species present
and then the connecting the
potential the electric potential of the
orbital reaction and then
each of these each of the reaction
comprises of half cell reactions
standard potential values
are not indicate stable now combine
combine the nathanian
we will generate the neural sequence the
learner's equation okay
and quantity guys is the concentration
of dissolved ions are dependent
uh the electric potential are dependent
to the concentration and have
standard reduction potential absolute
reaction for the species
now details attend for the zinc let's
say we want to know
the expression for the neural expression
of the zinc
so ayan two electrons here to effion
so we will derive dinner secretion
come up now these are just a further
derivation
for that the final equation here
is this one here ato
when the temperature is 25 degrees
celsius and take note guys
london's equation all of these standard
reduction potential
are measured were measured at 25 degrees
celsius
temperatures
so we have the equation here i am
the e
and so we have the e and we have the
derived shaft from the
g that gives free
gives free energy here then further
drive d shown d by
g sequence to negative nfe negative n
f e naught i and rt lone q so nfe nfe
and f
8.314 joules
per mole kelvin is a constant value
and then the phenomenon tina then is 25
degree celsius so 298.15 kelvin
and then f it is a 9 6
4 8 5 eight
five four five and engines because i
think it's
joules per mole i think
tools for balls wait i forgot
hello sorry for the equine i can't
call the units of n so the unit for this
is columns per mole yeah
columns per mole so my already little
guys is
will generate eight joules per column
which is equals two volts
so now and then we will generate this
where n is the number
of electrons number of electrons
in the reaction so this is will be the
our neurons equation
e is equals to e naught minus 0.0592
over n log q so another amount of
and then by the way you will have a
multiplier of
so we're done with that here
okay and so we're done with slide so the
nerd's equation for the complete cell
so this e right minus e left because the
positively charged
or positive side of the hour galvanic
cell is the cathode
while the negative side are cathode is
the quantity
it's the anode so right minus eleven so
minus zero okay
if we wish to express this okay now
let's express this down
into its connection and i forgot to
mention here
the q here in the expression of
current's equation
q is the reaction
quotient so what is the reaction
quotient
when
[Music]
so let's write the learner's equation
for this
overall reaction
is zero minus zinc zero point seven
six i plus plus in vinegar so negative
zero point seventy six and a half
so minus one minus in molar so positive
zero point seventy six
inert minus zero point zero
five nine one five parallel to five
length
nothing and then two sir
two electrons in present it is
so the zinc ion here so i we will
express this
in terms of concentration not activity
okay i also zinc capacity
all over the concentration of hydrogen
gas
all over the concentration of positive
squared bypasses by chemistry
system or the equilibrium expression
so that's how you express the now which
in turn
when we solve this sample problem
here so consider the galvanic cell
based on the reaction okay
uh we will discuss this on the next part
of our lecture i'm going to take
four five minutes so yeah we will
discuss
one and two three four
then five and then six
seven eight i am so iso
okay so that will be our discussion for
this lecture and
i hope you learned something see you on
the next
lecture which is mainly for us on the
problem solving
so goodbye class and see
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