Search found 16941 matches

by Chem_Mod
Fri Mar 08, 2019 1:38 am
Forum: Zero Order Reactions
Topic: definitions
Replies: 2
Views: 36

Re: definitions

It refers to the exponents on the concentrations. We designate these orders usually in terms of each reactant. So, in something like rate = k[A]0, reaction rate is independent of concentration of A itself. Thus, it's zero order with respect to A. Same idea for other orders.
by Chem_Mod
Fri Mar 08, 2019 1:36 am
Forum: Second Order Reactions
Topic: Third order reactions
Replies: 1
Views: 31

Re: Third order reactions

Basic rate law can be seen as rate (M/s) = k[A][B][....]. Essentially, rate is always measured in M/s. Thus, the right side's units has to cancel out to yield M/s. For a third order, there would be at least three concentrations on the right side of the equation. Thus, the rate constant has to have u...
by Chem_Mod
Fri Mar 08, 2019 1:33 am
Forum: First Order Reactions
Topic: First oder graphs
Replies: 2
Views: 44

Re: First oder graphs

So f(x) = ln(x) is itself exponential. However, we make ln[A] the x-axis. Because the x-axis and y-axis are measured with the same units, the graph is linear.
by Chem_Mod
Fri Mar 08, 2019 1:28 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining stability?
Replies: 1
Views: 50

Re: Determining stability?

Essentially, the one with a lower equilibrium constant would mean that reactants are favored, showing that the reactant is relatively more stable. Thus, Cl2, the reactant in its reaction, should be more stable than F2, which has a higher equilibrium constant.
by Chem_Mod
Thu Mar 07, 2019 10:01 pm
Forum: First Order Reactions
Topic: Half life of a first order reaction
Replies: 3
Views: 49

Re: Half life of a first order reaction

The half-life of a first order reaction does not depend on the initial concentration.
by Chem_Mod
Thu Mar 07, 2019 9:59 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2
Replies: 4
Views: 85

Re: Test 2

The idea is to calculate Kw at non-room temperature using Nernst Equation. When you know Kw, you can find the concentration of H3O+ in a neutral solution at that temperature by taking the square root of Kw and calculate the PH of the neutral solution.
by Chem_Mod
Thu Mar 07, 2019 9:55 pm
Forum: General Rate Laws
Topic: Ratios and Rate laws
Replies: 2
Views: 51

Re: Ratios and Rate laws

I assume you are referring to the method of the initial rate. Basically, if you double the initial concentration of a reactant A while keeping the concentrations of the other reactants the same, you can take the ratio of the rates. If the ratio is 1, the order with respect to A is 0, if the ratio is...
by Chem_Mod
Thu Mar 07, 2019 5:23 pm
Forum: Balancing Redox Reactions
Topic: balancing water
Replies: 8
Views: 92

Re: balancing water

Could you provide the question # so we can look at those as examples.
by Chem_Mod
Thu Mar 07, 2019 5:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 Problem 6 b&c
Replies: 1
Views: 58

Re: Test 2 Problem 6 b&c

Which test day are you talking about? Each day has a different version of Q6.
by Chem_Mod
Thu Mar 07, 2019 5:14 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition 14.37
Replies: 1
Views: 44

Re: 6th edition 14.37

The cell diagram is anode left and cathode right and based on that you can calculate the cell potential (Cathode - anode). If you have both gas and a.q when writing Q, use concentration for a.q and bar for gas.
by Chem_Mod
Thu Mar 07, 2019 4:40 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition, 14.37
Replies: 1
Views: 46

Re: 6th edition, 14.37

It is a concentration cell and the Cl- is free to move around between anode and cathode.
by Chem_Mod
Thu Mar 07, 2019 2:29 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 #5
Replies: 1
Views: 45

Re: Test 2 #5

The idea is to calculate Kw at non-room temperature using Nerst Equation. When you know Kw, you can find the concentration of H3O+ in a neutral solution at that temperature by taking the square root of Kw and calculate the PH of the neutral solution.
by Chem_Mod
Thu Mar 07, 2019 11:44 am
Forum: General Rate Laws
Topic: Deriving rate laws
Replies: 2
Views: 31

Re: Deriving rate laws

You should know the concepts.
by Chem_Mod
Tue Mar 05, 2019 10:42 am
Forum: General Rate Laws
Topic: K and k [ENDORSED]
Replies: 2
Views: 33

Re: K and k [ENDORSED]

K: equilibrium constant

k: rate constant

In class this week I will show and derive explicitly the relationship between rate constants and equilibrium constants.
by Chem_Mod
Mon Mar 04, 2019 6:05 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Unique/Formation and Degradation
Replies: 2
Views: 35

Re: Unique/Formation and Degradation

Unique rate is unique to the reaction; no matter with respect to which species the rate is measured, the unique rate calculated would be the same. The rate of formation/degradation is specific to one species in the reaction. It will be equal to the unique rate times the stoichiometric coefficient of...
by Chem_Mod
Mon Mar 04, 2019 5:51 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 2
Views: 33

Re: Rate Law

Yes, or in equations: Supposing r=[A]^x[B]^y[C]^z \frac{r_1}{r_2}=\frac{[A]_1^x[B]_1^y[C]_1^z}{[A]_2^x[B]_2^y[C]_2^z} \frac{r_1}{r_2}=\Big(\frac{[A]_1}{[A]_2}\Big)^x\Big(\frac{[B]_1}{[B]_2}\Big)^y\Big(\frac{[C]_1}{[C]_2}\Big)^z Supposing [B] and [C] don't change: \frac{r_1}{r...
by Chem_Mod
Mon Mar 04, 2019 5:16 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th Edition 14.41
Replies: 3
Views: 42

Re: 6th Edition 14.41

They chose to use n = 1 because they wrote Q as [H + ] 1 /[H + ] 2 which assumes the reaction is H + (aq) + 1 e – --> 1/2 H 2 (g) and the reverse. If they instead used 2 H + (aq) + 2 e – --> H 2 (g), then Q would be written [H + ] 1 2 /[H + ] 2 2 , and they would need to use n = 2. The answer comes ...
by Chem_Mod
Mon Mar 04, 2019 5:03 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gr vs G
Replies: 1
Views: 85

Re: Gr vs G

The convention is to write the absolute ∆G when it is written next to a reaction and the molar ∆G when it is written for a substance (∆G of formation of X, ∆G of combustion of Y). However, when it is written next to a reaction, it is still interpreted as ∆G per molar equivalent of the reaction as wr...
by Chem_Mod
Mon Mar 04, 2019 4:47 pm
Forum: General Rate Laws
Topic: 7C.5
Replies: 1
Views: 45

Re: 7C.5

The molecularity is the same as the sum of the exponents in the rate law for the elementary step
by Chem_Mod
Mon Mar 04, 2019 4:29 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7C.3 book example
Replies: 1
Views: 19

Re: 7C.3 book example

Can you please post the entire question for easy reference?
by Chem_Mod
Mon Mar 04, 2019 3:23 pm
Forum: General Rate Laws
Topic: units of rates and rate constants
Replies: 4
Views: 39

Re: units of rates and rate constants

Rate of a reaction is generally monitoring the change in concentration over time, thus M/s. For different order reaction, yes rate constants will vary in units, but rate will not.
by Chem_Mod
Mon Mar 04, 2019 1:23 pm
Forum: General Rate Laws
Topic: Derivatives
Replies: 5
Views: 48

Re: Derivatives

The integrated rate laws will be given to you. You will need to memorize which one is the first order rate law, which is second order, etc, unless you know how to derive them.
by Chem_Mod
Mon Mar 04, 2019 1:09 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th Edition 6N.3c
Replies: 2
Views: 50

Re: 7th Edition 6N.3c

Yes, as long as ∆G° or (equivalently) K was measured using the corresponding standard states.
by Chem_Mod
Mon Mar 04, 2019 1:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.91 6th edition
Replies: 1
Views: 34

Re: 14.91 6th edition

Current is the flow of charge. In the cell itself, the charges flowing are cations or anions in solution. Either the cations flow away from the anode through the salt bridge to the cathode, or the anions flow away from the cathode through the salt bridge to the anode, depending on the cell.
by Chem_Mod
Sun Mar 03, 2019 11:06 pm
Forum: General Rate Laws
Topic: Unique Average Rate versus Average Rate
Replies: 1
Views: 29

Re: Unique Average Rate versus Average Rate

Could you include an example question? If you are asked about the rate of consumption, it is more likely to be just the average rate.
by Chem_Mod
Sat Mar 02, 2019 9:53 pm
Forum: Zero Order Reactions
Topic: Units
Replies: 3
Views: 41

Re: Units

The rate law for a zero-order reaction is rate = k, where k is the rate constant. In the case of a zero-order reaction, the rate constant k will have units of concentration/time, such as M/s.
by Chem_Mod
Sat Mar 02, 2019 9:51 pm
Forum: Second Order Reactions
Topic: Reaction orders
Replies: 2
Views: 36

Re: Reaction orders

You have to look at the experimental data and determine the order.
by Chem_Mod
Sat Mar 02, 2019 9:50 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ion selective electrode
Replies: 1
Views: 25

Re: Ion selective electrode

Ion selective electrodes are membrane electrodes that produce potential by converting the activity of ions dissolved in a solution. The ion-selective electrode works based on the principle of a galvanic cell. It consists of a reference electrode, ion-selective membrane and voltmeter. The transport o...
by Chem_Mod
Sat Mar 02, 2019 9:29 pm
Forum: General Rate Laws
Topic: 1st order reaction
Replies: 1
Views: 20

Re: 1st order reaction

The order of a reaction refers to the power to which you have to raise the reactants in a specific chemical reaction to signify how they effect the rate of the reaction. For example, if the rate of the reaction were proportional to [A] (which is the concentration of a reactant labelled A), then this...
by Chem_Mod
Sat Mar 02, 2019 9:20 pm
Forum: General Rate Laws
Topic: Unique vs instantaneous rate
Replies: 6
Views: 65

Re: Unique vs instantaneous rate

AVERAGE RATE = (CONC(t2) − CONC(t1))/(t2 −t1) = ∆CONC/∆t INSTANTANEOUS RATE = −(d[R])/dt OR INSTANTANEOUS RATE = (d[P])/dt AVERAGE & INSTANTANEOUS RATES CAN BE DIFFERERENT FOR THE INDIVIDUAL R & P. THINK OF THEM AS THE EXPERIMENTALLY MEASURED RATES (COLLECTED DATA) OVER LONG TIME INTERVALS (...
by Chem_Mod
Sat Mar 02, 2019 8:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 96
Views: 29499

Re: Advice from a Medical Student [ENDORSED]

MCAT covers 14A-->D as well as biochemistry While this is a true statement, I would be careful about thinking that all courses are tested the same on the MCAT. There is a high importance placed on Chemistry 14A and 14B on the MCAT. There is s some 14C and 14D material, but more on 153A which is bio...
by Chem_Mod
Sat Mar 02, 2019 8:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 96
Views: 29499

Re: Advice from a Medical Student [ENDORSED]

Thank you so much! Would you say that any other chem classes were as helpful for the MCAT or did the MCAT only cover 14a and b material? Great question. While the MCAT does cover both general chem (Chem 14A/B) and organic chem (Chem 14C/D), I would say that the majority of the chem questions come f...
by Chem_Mod
Sat Mar 02, 2019 6:14 am
Forum: Balancing Redox Reactions
Topic: 6th edition, 14.5d
Replies: 1
Views: 34

Re: 6th edition, 14.5d

So for the reduction half reaction, you start with P4 --> PH3, and here are the steps to go through to balance it. 1. Balance the P's: P4 --> 4PH3 2. Balance the H's using H2O and OH- since we are working in a basic solution: P4 + 12H2O --> 4PH3 + 12OH- 3. Balance the charges: P4 + 12H2O + 12e- --> ...
by Chem_Mod
Sat Mar 02, 2019 5:56 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.23, part a
Replies: 2
Views: 36

Re: 14.23, part a

liquid mercury is a conductor so itself can conduct electron and no need to add another solid electrode
by Chem_Mod
Fri Mar 01, 2019 6:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L3 part d
Replies: 1
Views: 36

Re: 6L3 part d

So for this question, it's a good indicator that H2O water is involved. This is because there is no way we can go from O2 to H+ without H2O. One half reaction would go from O2 --> H2O. If you balance this, you can get the acidic form with the H+. To get the OH- form, you simply can add OH- to both s...
by Chem_Mod
Fri Mar 01, 2019 6:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.1
Replies: 1
Views: 44

Re: 6M.1

I believe this is a typo. Copper should be the anode. If you follow that notation, you should get the right answer. Come to office hours or peer learning sessions if you still have trouble with this.
by Chem_Mod
Fri Mar 01, 2019 6:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.9
Replies: 1
Views: 35

Re: 6L.9

So usually spectator ions are not included in the half reactions, so in this case, the half reactions would contain one with manganese and the other with iron (potassium and chloride are not included). You then balance each half reaction, and then balance the electrons so that you can add them toget...
by Chem_Mod
Fri Mar 01, 2019 4:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7a Help
Replies: 1
Views: 30

Re: 6L.7a Help

Hi Xuan,

You can think of it as one half reaction where Ag solid goes to Ag+ and the same for bromine. It seems like you have a lot of questions on Chem Community, so please come to scheduled peer learning sessions, TA OH, or Dr. Lavelle’s OH.

Thanks!
by Chem_Mod
Fri Mar 01, 2019 3:47 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 179
Views: 5643

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

Here is this week's worksheet focusing on reaction rates specifically differential rate law.
by Chem_Mod
Fri Mar 01, 2019 3:21 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 179
Views: 5643

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

could someone please explain #8 part a on the electrochemistry worksheet? How do we know that S2O8 2- is reduced and NO is oxidized? I also have this question You look at the chart of reduction potentials. The one with the higher reduction potential will be reduced. For the other half reaction, it ...
by Chem_Mod
Thu Feb 28, 2019 10:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: neutralization redox
Replies: 1
Views: 41

Re: neutralization redox

I'm assuming you're talking about the half reactions containing water, where one is in acidic conditions and the other is in basic conditions. Depending on the reagents in your cell and the reactions that take place, the reactions you use can vary. Perhaps if you have a specific example, we can work...
by Chem_Mod
Thu Feb 28, 2019 10:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 63L
Replies: 1
Views: 26

Re: 63L

The E values are usually given as reduction potentials. To find the overall E cell , you can use the equation E cell = E red + E ox . To get E ox , you would need to flip one of the reduction reactions/potentials to get the highest positive E cell . Once you flip one of the reduction reactions and f...
by Chem_Mod
Thu Feb 28, 2019 9:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy and Entropy
Replies: 6
Views: 92

Re: Gibbs Free Energy and Entropy

for a negative delta G, the sign of delta S can be both positive or negative
by Chem_Mod
Thu Feb 28, 2019 8:39 pm
Forum: Balancing Redox Reactions
Topic: Question 6K.3 part (d)
Replies: 1
Views: 21

Re: Question 6K.3 part (d)

Can you please use a screenshot or take a pic to show what you are asking?
by Chem_Mod
Thu Feb 28, 2019 6:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrolytic cell
Replies: 1
Views: 26

Re: Electrolytic cell

Current flows opposite to the flow of electrons.
by Chem_Mod
Thu Feb 28, 2019 6:43 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Element's potentials
Replies: 5
Views: 73

Re: Element's potentials

It varies depending on the elements, but one factor is the relative stability of the product that is formed after a redox reaction. As long as the reaction is overall spontaneous, it will be favorable to occur.
by Chem_Mod
Thu Feb 28, 2019 6:41 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6th edition, 14.33
Replies: 1
Views: 37

Re: 6th edition, 14.33

The redox couple just refers to a transfer of electrons between the two species in that couple. The idea here is to find the delta G for the disproportionate reaction to determine whether this reaction is spontaneous or not. If it's spontaneous, it will proceed. If not spontaneous, then it will not ...
by Chem_Mod
Thu Feb 28, 2019 6:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentrations product versus reactant
Replies: 1
Views: 57

Re: Concentrations product versus reactant

Since Y3+ comes from Y(NO3)3, we can conclude that the Y3+ from this yttrium nitrate is the reactants. The reason being because there really isn't any other source of Y3+, meaning that the Y3+ from this must be the reactant. Thus, the Y3+ in the saturated solution must be the products.
by Chem_Mod
Thu Feb 28, 2019 6:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 7th Edition Problem 6M 1
Replies: 1
Views: 27

Re: 7th Edition Problem 6M 1

Since the M electrode is on the left, it is assumed to be the anode for the purpose of measuring the cell potential; therefore, the Cu electrode is the cathode. The M(s)|M+(aq) is probably a typo and should be M(s)|M2+(aq).
by Chem_Mod
Thu Feb 28, 2019 6:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: standard molar entropy vs entropy of formation
Replies: 1
Views: 35

Re: standard molar entropy vs entropy of formation

The difference is mainly in what formation is. Formation is the reaction that includes reactants that are basic elements and one product that is 1 mole of the compound the entropy is for. Entropy of formation is the change in heat associated with formation of 1 mole of compound, whereas standard mol...
by Chem_Mod
Thu Feb 28, 2019 6:22 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.17
Replies: 3
Views: 42

Re: 11.17

The problem gives you information about the K value and concentrations that can be used to get the Q value. ΔG = ΔG0 + R*T*ln(Q) can then be used to calculate the ΔG.
by Chem_Mod
Thu Feb 28, 2019 6:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.15 6th Edition
Replies: 2
Views: 35

Re: 11.15 6th Edition

You're right in that it is nonspontaneous when producing I, but when producing I2, it is spontaneous because it is in the opposite direction.
by Chem_Mod
Thu Feb 28, 2019 6:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th edition, 14.17
Replies: 2
Views: 43

Re: 6th edition, 14.17

The best way to tackle these kinds of problems is to practice. When a half reaction contains permanganate, it's always going to have a redox pair between MnO 4 - and Mn 2+ . Same thing with iron, as the redox pair is usually between an Fe 2+ and an Fe 3+ . Whenever you want to balance oxygens, we us...
by Chem_Mod
Thu Feb 28, 2019 6:10 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: pH meter
Replies: 1
Views: 48

Re: pH meter

A pH meter is an example of an ion-selective electrode. The pH meter has a thin-walled glass membrane that measures the [H+] difference between a standard known [H+] concentration inside the pH meter and that of solution the meter is placed in. This [H+] difference is used to find the pH of the solu...
by Chem_Mod
Thu Feb 28, 2019 5:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Adding inert electrode to cell diagram
Replies: 1
Views: 30

Re: Adding inert electrode to cell diagram

They are called inert so that they do not react when the redox reaction progresses. Electrodes are necessary for redox reactions to occur, so it's good to have electrodes that won't participate in your reaction.
by Chem_Mod
Thu Feb 28, 2019 4:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ΔG is slope? [ENDORSED]
Replies: 1
Views: 81

Re: ΔG is slope? [ENDORSED]

ΔG is the slope of the line at each composition because the system is not at equilibrium and therefore, as I discussed in class, the concentration of reactant and product is changing and therefore so is ΔG.

Unlike ΔGo which is a fixed value for a given reaction.
by Chem_Mod
Thu Feb 28, 2019 4:04 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ion-selective electrodes [ENDORSED]
Replies: 1
Views: 54

Re: Ion-selective electrodes [ENDORSED]

I mentioned the most common in class. There are additional ion-selective electrodes.
by Chem_Mod
Thu Feb 28, 2019 1:54 pm
Forum: Balancing Redox Reactions
Topic: 7th edition 6K.3.d.
Replies: 1
Views: 20

Re: 7th edition 6K.3.d.

The Cl2 on the right side should be Cl-, it is a typo
by Chem_Mod
Thu Feb 28, 2019 12:36 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: stoichiometric coefficients
Replies: 2
Views: 18

Re: stoichiometric coefficients

No, it doesn't, cell potential is an intensive property
by Chem_Mod
Thu Feb 28, 2019 7:05 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Including Electrode in Cell Diagram
Replies: 2
Views: 38

Re: Including Electrode in Cell Diagram

An inert electrode is required whenever their is no conducting metal. When the participants in a half-reaction are all in the aqueous phase, an electrode, i.e. a solid surface, is needed for the electron transfer.
by Chem_Mod
Thu Feb 28, 2019 7:01 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th edition, 14.15b
Replies: 1
Views: 29

Re: 6th edition, 14.15b

It says that they are using the Bronsted Neutralization reaction and so that incorporates the half reactions O2 + 4H+ +4e- 2H2O O2 + 2H2O + 4e- -> 4OH- While the other half reactions might yield the same electric potential, it does not satisfy the neutralization reaction as it does not involve and a...
by Chem_Mod
Thu Feb 28, 2019 6:54 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: van hoff and ph
Replies: 1
Views: 29

Re: van hoff and ph

The idea is to figure out the H3O+ concentration from the Kw, Kw at different temperatures can be calculated by using the van hoff equation.
by Chem_Mod
Thu Feb 28, 2019 6:49 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram: solids
Replies: 1
Views: 30

Re: cell diagram: solids

It is indicating that the outside of the vertical line is the electrode.
by Chem_Mod
Thu Feb 28, 2019 6:45 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: internal energy
Replies: 3
Views: 51

Re: internal energy

No, only for isothermal irreversible process the change in internal energy is 0
by Chem_Mod
Thu Feb 28, 2019 6:40 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram notation
Replies: 2
Views: 29

Re: Cell Diagram notation

The species in the same phase are separated by comma while different phases will be separated by a single vertical line
by Chem_Mod
Thu Feb 28, 2019 6:37 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagrams and undissolved solids in solution
Replies: 1
Views: 24

Re: Cell diagrams and undissolved solids in solution

Electrodes are conducting metals and solid state salts are usually insulators
by Chem_Mod
Thu Feb 28, 2019 6:34 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: writing cell diagrams
Replies: 1
Views: 28

Re: writing cell diagrams

When the reaction does not have conducting metals, platinum or graphite, both inert conductors, are incorporated into the cell diagram as an electrode to transfer electrons.
by Chem_Mod
Thu Feb 28, 2019 6:31 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.5
Replies: 1
Views: 22

Re: 6L.5

Au is in the reaction and is a good conductor.
by Chem_Mod
Thu Feb 28, 2019 6:29 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L. 3
Replies: 1
Views: 25

Re: 6L. 3

It is H2O going to H+ and O2 on the anode, while H2O and O2 going to OH- on the cathode
by Chem_Mod
Thu Feb 28, 2019 6:26 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E
Replies: 4
Views: 53

Re: E

You need to covert E to delta G and then add because delta G is a state function
by Chem_Mod
Thu Feb 28, 2019 6:25 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: van hoff
Replies: 1
Views: 27

Re: van hoff

Yes, you need to know the Van hoff equation.
by Chem_Mod
Thu Feb 28, 2019 6:21 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram h2o
Replies: 1
Views: 22

Re: cell diagram h2o

If H2O is just the solvent showing the reaction happens in aqueous solution, it is not included in the cell diagram
by Chem_Mod
Thu Feb 28, 2019 6:20 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Why can't we add standard cell potentials?
Replies: 1
Views: 20

Re: Why can't we add standard cell potentials?

Because number of eletron transfer for two reactions might be different and you need to take that into consideration, converting E to delta G and then add.
by Chem_Mod
Thu Feb 28, 2019 6:18 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Gibbs free energy of elements
Replies: 1
Views: 23

Re: Standard Gibbs free energy of elements

Because if you write the formation reaction it is A--->A so the final and initial state are the same
by Chem_Mod
Thu Feb 28, 2019 6:17 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram h2o
Replies: 1
Views: 22

Re: cell diagram h2o

If H2O is just the solvent showing the reaction happens in aqueous solution, it is not included in the cell diagram
by Chem_Mod
Thu Feb 28, 2019 12:44 am
Forum: Student Social/Study Group
Topic: Fridays lecture notes
Replies: 1
Views: 58

Re: Fridays lecture notes

During lecture, you may also ask around if you can take pictures of their notes!
by Chem_Mod
Thu Feb 28, 2019 12:43 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 7th Edit 6M5
Replies: 1
Views: 28

Re: 7th Edit 6M5

Please post full questions and or screenshot because not everyone has the 7th edition.
by Chem_Mod
Thu Feb 28, 2019 12:42 am
Forum: Student Social/Study Group
Topic: Lyndon's workshop
Replies: 1
Views: 143

Re: Lyndon's workshop

We will see what can be done about a bigger room.
by Chem_Mod
Wed Feb 27, 2019 7:39 pm
Forum: Balancing Redox Reactions
Topic: 6th Edition, 14.1 [ENDORSED]
Replies: 1
Views: 34

Re: 6th Edition, 14.1 [ENDORSED]

Sure! Let's look at the breakdown of the oxidation numbers. We know that H has an oxidation number of +1, and oxygen is usually (-2). As such, C 2 H 5 OH has a -2 from Oxygen and a +6 from Hydrogen, with an overall +4. To produce the neutral charge on the molecule, C must balance this out. There are...
by Chem_Mod
Wed Feb 27, 2019 7:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th edition 14.13 d [ENDORSED]
Replies: 5
Views: 90

Re: 6th edition 14.13 d [ENDORSED]

Yes, because you do not have a half reaction using Ag+, and you would need a conducting electrode, you would simply use Ag(s) as your conducting electrode.
by Chem_Mod
Wed Feb 27, 2019 7:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt (s) [ENDORSED]
Replies: 8
Views: 68

Re: Pt (s) [ENDORSED]

The above answers are correct! Great job, everyone. As for the homework problem, many students get confused by the solid I 2 . You need to remember that not all solids are conductors. You must have a metal for it to conduct, and I 2 is not a conducting metal. Therefore, you need to add Pt as an elec...
by Chem_Mod
Wed Feb 27, 2019 7:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell Diagram [ENDORSED]
Replies: 3
Views: 54

Re: Galvanic Cell Diagram [ENDORSED]

All phases are separated by a line, so you would put a line between the gaseous phase and the aqueous phase.
by Chem_Mod
Wed Feb 27, 2019 7:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th edition 14.31
Replies: 1
Views: 26

Re: 6th edition 14.31

It is the oxidizing agent because it is being reduced. This is an easy thing to confuse. Just remember that when something is an agent, it is talking about what effect that compound has on another compound. In this case, nitrate takes electrons to become nitrate, and is being reduced, therefore it m...
by Chem_Mod
Wed Feb 27, 2019 7:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7b
Replies: 1
Views: 31

Re: 6L.7b

You need to balance this using elemental oxygen.
by Chem_Mod
Wed Feb 27, 2019 7:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta Sm versus delta Sf [ENDORSED]
Replies: 1
Views: 36

Re: delta Sm versus delta Sf [ENDORSED]

The entropy of melting is a different process than the entropy of formation. Because these are two different processes, they will not have the same entropy. Formation is via the compounds constituents, and melting would be changing from solid to liquid.
by Chem_Mod
Wed Feb 27, 2019 7:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15b 6th ed
Replies: 1
Views: 34

Re: 14.15b 6th ed

Water is always omitted from cell diagrams.
by Chem_Mod
Wed Feb 27, 2019 7:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H2O in cell diagrams
Replies: 1
Views: 34

Re: H2O in cell diagrams

You would only include water if it is the thing being oxidized or reduced, but never to represent aqueous solvent.
by Chem_Mod
Wed Feb 27, 2019 7:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Potential Energy Gradient [ENDORSED]
Replies: 1
Views: 30

Re: Potential Energy Gradient [ENDORSED]

The more positive an E value is, the more potential energy it has if it is being reduced. The specificity on potential energy of an anode or cathode is dependent on the specific half reaction.
by Chem_Mod
Wed Feb 27, 2019 7:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.13 in 7th edition
Replies: 1
Views: 23

Re: 6M.13 in 7th edition

For the cathode side of the cell diagram, aqueous compounds are written before gaseous compounds. I am unclear about what you are asking in the second part of your question.
by Chem_Mod
Wed Feb 27, 2019 7:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.3
Replies: 2
Views: 34

Re: 6M.3

Can you clarify what you mean by it not being included for the anode? In the way you have written it, it is included in the anode.
by Chem_Mod
Wed Feb 27, 2019 7:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 6th edition, #89
Replies: 1
Views: 19

Re: 6th edition, #89

Can you please post the question and answer for reference?
by Chem_Mod
Wed Feb 27, 2019 7:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Example 19.14 (6th edition)
Replies: 1
Views: 18

Re: Example 19.14 (6th edition)

Can you clarify what homework question this is regarding and perhaps write out the problem? 19.14 is not one of the homework problems you are responsible for, nor is that chapter related to Gibb's Free Energy.
by Chem_Mod
Wed Feb 27, 2019 7:15 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 7th Edition
Replies: 1
Views: 35

Re: 6K.5 7th Edition

Can you please post the text of the question for reference?

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