LECTURE 11 REFLECTION_STANDARD ELECTRODE POTENTIAL REVISION AND NERNST EQUATION by Pooganeswari Siteram Pillai

Arwen_JC2 T

2021-09-20 09:23:25 UTC

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Recall:

metal-metal ion half-cell
non-metal/non-metal ion half-cell
ion/ion half-cell

*when drawing, check the equation first // H+ ions will always have 3 aqueous solutions with the concentration of 1.00 mol/dm3

Standard cell potential

value more positive, to the right
value more negative, to the left

Predicting feasability of reactions

more positive values of Eø -> stronf oxidising agent
predict through rearrangement of equations and values from data booklet

*strong oxidising agents must pair (match) with strong reducing agents

Nerst equation

"how value of an electrode potential varies with the concentrations of the aqueous ions"
E = Eø + (0.059/z) log (oxidised species/reduced species)
(old syllabus) E = Eø + 0.059/2 log10(oxidised form)

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I think I have to understand the half-cells and the equations better and I have to revise how to write half equations.

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I liked the lesson; it flows nicely and is very straightforward.

Elizabeth Donna

2021-09-20 09:32:33 UTC

Standard electrode potential
- Compare with standard H2 electrode
- Temp : 25 degree C

Indicate electron flow
- Indicate External circuit

Predicting the feasibility of the reaction
- SOA (Strong oxi agent) [Top] -> tendency to go right , gain electrons , stongest oxi agent
- more positive top , less positive bottom
- Positive : feasible , Negative : Non feasible

Non standard condition
- use LCP : To find direction
* Right (more positive)
* Left (more negative)

- Can only predict if E standard more than 0.30V, if it is less 0.30V it cannot be predicted

Nerst equation
- Effect of conc and temp on (Ecell)
- Oxi Form : Left , Reduce Form : Right

- Practice more ques
- learn more about nerst equation
- Remember SOA and SRA chart

Jasmine JC2T

2021-09-20 09:34:23 UTC

- strong oxidising agent -> on the left, going to the right ( positive )
- strong reducing agent -> on the right, going to the left ( negative )
- non standard conditions -> use LCP if E standard difference is >0.30V
- nerst equation
- positive E value -> feasible
- negative E value -> non feasible

Study more on :
Nerst equations
( memorise formulas )

Teaching was good and detailed

Catherine

2021-09-20 09:38:40 UTC

Reviewed on: electrochemical cells, how to draw and how to measure

Learnt:

direction of electron flow
feasibility of reaction (more positive, stronger oxidizing agent)
NERST equation (for non standard conditions)
Only valid if E standard difference greater than 0.3V

The lesson was clear and easy to understand. I should study more on how to use the NERST equation.

Ella JC2G

2021-09-20 10:01:33 UTC

I have learnt the following:

There are two methods that can be used to fins out whether a reaction is feasible:

Without calculation: Identify the reduction reaction which has a more positive SEP value and identify the SOA and SRA.
With calculation: Determine which reaction will be forward or backward (change sign) through the previously mentioned method and add the SEP values together. If the sum is +, the reaction is feasible.

When the experiment is not conducted under standard conditions (change in conc), the change in EP will be determined by the LCP.
However, the prediction is only valid then the SEP difference is above 0.30 V. In this case, the Nernst Equation can be used to calculate the SEP.
There are two forms of the equation. However, the latter, simplified version can only be used when the temperature is 298K.
The SEP and Gibbs Free Energy can be related in the following equation: delta G = -nF(E cell).
When both E cell is positive, delta G must be negative, so the reaction is feasible.
I need to memorise the equations. Teaching was great and elaborate.

Benedict JC2T

2021-09-20 10:18:59 UTC

Today i revised about electrode potential again. We revised what the positive and engative E values mean.

Predicting feasibility
- Feasibility can be predicted using the E values.
- Feasibile here means if one element/compound can oxidise the other.

Method:
- The more positive E value will be able to oxidise the one with the more negative E value.
- If the difference of the E values of both reactions are less than 30, it is unable to react.

The changing of Concentration
- The higher concentration, the more positive the reaction will be
eg. more than 1 mol dm^-3 will make the E value more positive
- The lower concentration, the less positive the reaction will be
eg. less than 1 mol dm^-3 will make the E value less positive

When the experiment is not done under standard conditions, Nernst Equation must be used.
We use LCP to determine wether the E value will go up or down.
if the difference in E values are less than 30, the two ions cannot react with eachother and we cannot use the method to determine if the reaction will be feasible or not.
When writing down the half equations, the oxidised state should be on the left while the reduced state should be on the right.

I need the understand the fundamentals better and memorize all the conditions and equations. I need to revise on the electrode potentials especiallt eh ion/ion ones. The lesson was easy to understand and several revisions allowed me to not miss much.

Davis JC2Grace

2021-09-20 10:24:02 UTC

During the lecture i learnt about,

- Predicting the feasibility of reaction
- Total SEP value positive = feasible
- Total SEP value negative = not feasible
- Direction of elecrtron flow
- The order of the SOA and SRA
- NERNST Equation and the formula

I need to review on:
NERNST EQUATION

Teaching was clear and detailed.

Michael jc2t

2021-09-20 10:34:18 UTC

Predicting feasibility of the reaction. The one at the top left is SOA: strong oxidizing agents. Oxidizing agents will always oxidize reducing agents. Bottom right Strongest reducing agent. Strong oxidizing agent will always try to oxidize strong reducing agent. Rearrange bigger E value at the top and smaller E value at the bottom. If E value is positive, reaction is feasible. If E value is negative, reaction is not feasible. Standard condition: 25 degree Celsius and 1moldm-3.

Josh JC2Truth

2021-09-20 10:35:17 UTC

Feasibility can be predicted when using the E values. Feasible means when if one element or compound can oxide with the other. It is spontaneous.

The more positive E value can oxidize with the more negative E value, however, if the differences of the both reactions are less than 30, it cannot react.

The higher concentration, the more positive a reaction will be. The lower concentration, the less positive a reaction will be.

Nerst Equation
It is how much of an electrode potential varies with the concentrations of the aqueous ions.
Left is Oxidation form
Right is Reduction form

The lesson was good as usual and very simple to follow. 👍

Frederic JC2T

2021-09-20 10:57:09 UTC

Feasibility can be predicted by using E values only if the difference is more than 0.3V. Feasible means that one element can can oxidize the other and one element can be reduced as well similar to a redox reaction. Positive value of V indicates that the reaction is feasible
The concentration effects the feasibility of a reaction and will shift to balance the change. A higher concentration in the right side will make the voltage more positive and a higher concentration in the left side of the reaction will decrease the voltage of the reaction.

Nerst equation is the value of an electrode potential that varies with the concentrations of the aqueous ions"

Formula; E = Eø + (0.059/z) log (oxidised species/reduced species)

SOA( more negative)
SRA( more positive)

Megan JCT

2021-09-20 11:18:00 UTC

Today I learnt :
-How to predict feasibility of reactions :
* More positive E values mean they are feasible.
* Negative values E values mean they are non feasible
-Valid prediction is is E standard difference is greater than 0.30 V
-Most positive E value = SOA
-Most negative E value = SRA
Non Standard Conditions :
-If conc. is increased, E value becomes more positive.
-If conc. is decreased, E value becomes more negative.
What I need to revise on :
- NERST Equation formula
-How to calculate the electrode potential

The lesson was very easy to undestand.

Nevan Kho

2021-09-20 12:13:46 UTC

2 methods to predict feasibility

1. arrange equations in reducing forward reaction. equation with more positive e value on top. top left is SOA, bottom right is SRA. they can react with each other.

2. larger E value means that reaction will proceed in the forward reaction. If the half equations go in opposite directions, it will react.

nernst equation, how to calculate the e value under non standard equations.

Kevin JC2T

2021-09-20 13:06:06 UTC

Predicting feasibility of reaction:
1.- strong OA -> more positive values
2. non-standard conditions -> use LCP if E standard difference is more than 0.30V
3. Nerst equation :
positive E value is feasible
negative E value is non feasible

Geoffrey

2021-09-20 13:14:41 UTC

Predicting the feasibility of the reaction
- Strong oxi agent tendency to go right , gain electrons.
- more positive top , less positive bottom
- Positive : feasible
-Negative : Non feasible

Non standard condition
- use LCP : To find direction
-Right (more positive)
-Left (more negative)

Predicts if E standard more than 0.30V, if it is less 0.30V it cannot be predicted

Nerst equation
- Effect of conc and temp on E cells
- Oxi Form : Left
-Reduce Form : Right

Wilson JC2T

2021-09-20 14:42:02 UTC

Throughout this lecture, I learnt about how to predict the feasibility of reaction. I also revised about how strong oxidizing agents have a tendency to shift to the right and strong reducing agent is the opposite. I also learnt about the NERST equation and revised on how to draw half cell.

Raphael JC2G

2021-09-20 15:09:30 UTC

Predicting the feasibility of a reaction using:

1. A forward reduction reaction where the more positive reaction is on top and the more negative reaction is on the bottom. the top left of the reaction is the strong oxi agent and the bottom right is the strong reducing agent.

2. NERST equation means that a more positive E value is feasible while a more negative E value is non-feasible

3. Prediction using E when the difference between the reactions is greater than 0.3V

Ashley JC2G

2021-09-20 17:07:43 UTC

We revised on standard electrode potential, and learnt more on feasibility.

1. Rearrange the equations (with one in reducing form and the other in oxidising form). Ensure the one in oxidising form's electrode potential is multiplied by -1. The one on the top left is the strongest oxidising agent, the one on the bottom right is the strongest reducing agent. See if the reaction is feasible.

2. Calculate the voltage, (ensuring that it's flipped, the correct electrode potential is multiplied by -1. If the voltage is > 0, then it is feasible. If it is < 0 , then it is not.

idk what the NERNST equation is and I'm scared.

The teaching was great, was like a church sermon as always.

Cleantha

2021-09-20 18:23:31 UTC

1. The more positive it is, it will be a weaker reducing agent but a strong oxidising agent. The more negative it us, I is a weaker oxidising agent but stronger reducing agent. Oxidising agent will get reduced and whichever is more positive, will have a higher chance to go to the right.

There are to methods that can be used in predicting feasibility.

The strongest oxidising agent usually reacts with the weakest oxidising agent which also is the strongest reducing agent. Rearrange so more positive E value is at the top while less positive is at the bottom.

Second method is related to what we learned before. More positive goes to the right while the less go to the left.

The last part should be about Nernst equation
2. The last part
3. It's easy to understand andfollow

Jennifer JC2G

2021-09-20 21:30:29 UTC

Predicting the Feasibility of the Reaction
- The more negative, the greater reducing agent, the greater possibility of oxidation reaction
- The more positive, the greater oxidizing agent, the greater possibility of reduction reaction
∆Gø = - (n)(F)(Eøcell)
∆G = Standard Gibbs
n = mol
F = Faraday = 96 500
Eø cell = Standard Cell potential

Nernst Equation
E = Eø + [RT/zF ln (oxidized/reduced)]
E = Electrode potential
Eø = Standard Electrode potential
R = Gas constant = 8.31
T = Temperature (K)
z = # of electrons transferred
F = Fara day's constant
ln = Log
Oxidized = Conc. of oxidized form

- I need to learn more on how to calculate
- Teaching was good

sharon jc2T

2021-09-21 00:49:22 UTC

Revision on standard electrode potential and nernst equation

Standard electrode potential : comparing with standard hydrogen electrode

25 degree celsius
1 atm
Concentration of 1 mol/dm3

Measuring standard electrode potentials

metal/metal ion half cell
- Needs to be in standard reduction form (equation)
non-metal/non-metal ion half cell
- Needs to be in standard reduction form (equation)
- Non metal is gas
- Exception : Iodine in solid form (at the bottom of the beaker)
ion/ion cell half cell
- Needs to be in standard reduction form (equation)
- Aqueous form
- If there is presence of H+, do not forget about it (need to put one mole of H+ in it). So total 3 concentrated solution

Using E standard

Standard cell potential can be calculated for two half cells
See which one is more positive. If more positive, shifted to the right
Balance the equation first
Don’t times E value, but do sign change

E standard values and flow of electrons

Always indicate direction on external circuit
From negative to positive

Predicting the feasibility of the reaction

More positive E value, strongest oxidising agent and weakest reducing agent
More negative E value, weakest oxidising agent and strongest reducing agent
Strongest oxidising agent will react with strongest reducing agent
Strong oxidising agent will always try to oxidise strong reducing agent
Positive value : feasible, negative value : non-feasible

Nernst equation

Non-standard condition
Use LCP
How to predict?
- Valid prediction if E standard difference is greater than 0.30 V
- Non valid/unexpected outcome if E standard difference is less than 0.30 V
Equation see from textbook

teaching was great and easy to understand

michelle jc2grace

2021-09-21 00:56:56 UTC

i learnt about nernst equation, positive value means its feasible while negative value means its non feasible. Nernst equation is also a non standard condition. prediction is only valid when E standard difference is more than 0.30V. i also learnt about SOA (more negative) - strong oxidizing agent, SRA(more positive)- strong reducing agent. I also learnt about the formula or nernst equation and the formula.

need to study on the nernst equation more because im still not that fluent in calculating that.

teaching was great like usual, very detailed and easy to understand.

Thomson JC2T

2021-09-21 01:05:53 UTC

Half cell is cells connected to standard hydrogen electrode. The cell can be:

metal/metal ion
non-metal/nonmetal ion
ion/ion

Nernst equation we need to use LCP to predict negativity of an electrode and the difference need to be more than 0.3

Positive E value means the reaction is feasible and negative E value means it is not

-I need to memorize the equation and learn how to use them-

Strong oxidising agent is more negative and strong reducing agent is more ppositive

Keira JC 2 Grace

2021-09-21 07:30:11 UTC

standard electrode potential conditions
- concentration of ions at 1.00moldm-3
- temperature of 25°C (298K)
- gasses at 1atm (101kPa)

measure standard electrode potentials
- equation needs to be in reduction form
- metal/metal ion half cell
- non metal/non metal ion half cell
- ion/ion cell half cell

nernst equation
- prediction is only valid when E standard difference is more than 0.30V (using LCP)
- more positive E value will be the oxidising agent (feasible)
- strong oxidising agents go to the right, to gain electrons

I need to review more on the nernst equation. However, teaching was clear with a lot of example questions to make the lesson more understandable.

Jonathan

2021-09-21 07:39:13 UTC

We can predict the feasibility of a reaction by comparing their standard electrode potentials, and checking whether the result after adding is positive or negative, a positive value meaning it is feasible. I also learnt about the nernst equation, which tells us how to predict feasibility under non standard environments. I need to memorise the equation better.

Ryan JC2Truth

ryanant2004 — 2021-09-21 15:17:00 UTC

I learned how to predict the feasibility of the reaction. More positive E value means they are more feasible, while having a negative E value means its non feasible. I also learned about the oxidizing and reducing agent. Strong oxidizing agent will try to oxidize the strong reducing agent. The standard condition is 25 degree celcius and 1 mol/dm3. I also learned about the NERNST Equation.

Dylan JC2G

2021-09-24 17:09:59 UTC

Standard Electrode Potential (E°)
- The standard electrode potential for a half-cell is the voltage measured under standard conditions with a standard hydrogen electrode as the other half-cell.

Conditions:

- Concentration of ions at 1.00 mol dm-3

- Temperature of 25 °C (298K)

- Pressure of 1 atm (101kPa)

Measuring standard electrode potentials
( equations needs to be in reduction form )
- metal/ metal ion half cell
- non-metal/ non-metal ion half cell
- ion/ion cell half cell

Predicting feasibility of reactions

- we can use G = -nFE where n = number of moles of electrons, F = faraday, and E = standard cell potential
- More positive E values = feasible
- More negative E values = non-feasible
- Feasibility can be predicted by using E values only if the difference of the E values is more than 0.3V.

Nerst equation (non standard condition): E = standard E + (RT/zF) • ln(ox/red)

The simplified formula can only be used when T is 298K (the one using lg), otherwise use the full formula.