Introduction to Electrochemistry (Part 1)

Summary

This 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

• 🔋 Electrochemistry is the study of chemical reactions that produce or require an electric current, converting chemical energy into electrical energy within an electrochemical cell.
• 🔬 The main components of an electrochemical cell include electrodes, a voltmeter, a salt bridge, and beakers containing solutions where oxidation and reduction occur.
• 📍 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.
• 🚫 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.
• 🔄 The salt bridge's purpose is to maintain electrical neutrality in the solutions, allowing ions to move freely to balance the charge.
• 🔌 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.
• 🌡️ The Nernst Equation is temperature-dependent, with standard reduction potentials measured at 25 degrees Celsius.
• 🔄 The overall cell potential is calculated by subtracting the standard reduction potential of the anode from that of the cathode in a galvanic cell.
• 📝 Line notation is used to write the reactions in electrochemical cells, indicating changes in state, concentrations, and the junction between half-cells.
• 🔍 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

00:00

🔬 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.

05:02

🔋 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.

10:05

🔍 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.

15:05

🌐 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.

20:06

📚 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.

25:07

🔄 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.

🔚 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.

Keywords

💡Electrochemistry

Electrochemistry is the study of chemical reactions that produce or require an electric current. It involves the conversion of chemical energy into electrical energy or vice versa, typically within an electrochemical cell. In the video, electrochemistry serves as the overarching theme, with the lecture focusing on the fundamentals of electrochemical cells, their components, and how they function.

💡Electrodes

Electrodes are the conductive elements in an electrochemical cell where oxidation and reduction reactions occur. The anode is the electrode where oxidation takes place, and the cathode is where reduction occurs. In the script, the lecturer explains the roles of anodes and cathodes in both galvanic and electrolytic cells, emphasizing their importance in driving electrochemical reactions.

💡Galvanic Cell

A galvanic cell, also known as a voltaic cell, is a type of electrochemical cell that generates an electric current through spontaneous redox reactions. The script describes the galvanic cell setup, including the electrodes, salt bridge, and the generation of electric current without the need for external electrical energy.

💡Electrolytic Cell

An electrolytic cell is an electrochemical cell that facilitates non-spontaneous redox reactions by applying electrical energy, a process known as electrolysis. The lecturer in the video explains how electrolytic cells differ from galvanic cells and the conditions under which they operate, including the use of an external voltage to drive chemical reactions.

💡Voltage and Cell Potential

Voltage, or cell potential, is the measure of the electric potential difference between the electrodes in an electrochemical cell. It is a key concept in the video, as it is used to describe the driving force behind electrochemical reactions and is related to the cell's ability to perform work, such as in a galvanic cell generating a positive voltage.

💡Salt Bridge

A salt bridge is a component of an electrochemical cell that maintains electrical neutrality by allowing the movement of ions between the two half-cells. In the script, the lecturer mentions the purpose of the salt bridge in facilitating the flow of ions, which is essential for the continuation of electrochemical reactions.

💡Ohm's Law

Ohm's Law relates the voltage (V), current (I), and resistance (R) in an electrical circuit, expressed as V = IR. While not the main focus of the video, Ohm's Law is mentioned in the context of measuring electric current in electrochemical cells, illustrating the relationship between electrical properties in these systems.

💡Standard Reduction Potential

Standard reduction potential is a measure of the tendency of a chemical species to gain electrons and undergo reduction under standard conditions. The video script discusses how this value is used to compare the oxidizing power of different species and to calculate the overall cell potential of an electrochemical cell.

💡Nernst Equation

The Nernst Equation is used to determine the cell potential of an electrochemical cell under non-standard conditions, taking into account the concentrations of the species involved in the redox reaction. The lecturer explains the significance of this equation in calculating the cell potential based on the concentrations of reactants and products.

💡Reduction-Oxidation (Redox) Reaction

A redox reaction involves the transfer of electrons between chemical species, with one species being oxidized (losing electrons) and another being reduced (gaining electrons). The script emphasizes the central role of redox reactions in electrochemistry, as they are the basis for the functioning of both galvanic and electrolytic cells.

💡Line Notation

Line notation is a method of writing electrochemical cell reactions, indicating the components and the direction of electron flow. The video script provides examples of how to write line notation, including the representation of half-cell reactions, the use of single and double vertical lines, and the notation for anodes and cathodes.

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