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by Ryan Lee 1E
Wed Mar 11, 2020 11:00 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Fast Step/Slow Step
Replies: 7
Views: 66

Re: Fast Step/Slow Step

I believe that if it had multiple steps, they would either give you experimental data to determine the slow step or they would just tell you what the rate-limiting step is.
by Ryan Lee 1E
Wed Mar 11, 2020 10:53 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis
Replies: 2
Views: 73

Re: Electrolysis

I pulled this from Google: "Electrolysis is used extensively in metallurgical processes, such as in extraction (electrowinning) or purification (electrorefining) of metals from ores or compounds and in deposition of metals from solution (electroplating)." It appears that it's used for gett...
by Ryan Lee 1E
Wed Mar 11, 2020 1:20 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Bottle Neck Effect
Replies: 4
Views: 75

Re: Bottle Neck Effect

I believe the bottleneck effects describes when in a reaction with multiple steps, there is a slow step that follows a fast step, which means that the second step limits how fast the first one can go (the bottleneck). This is applied to the pre-equilibrium approach we have in which if the first fast...
by Ryan Lee 1E
Wed Mar 11, 2020 1:12 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.7
Replies: 3
Views: 51

Re: 7D.7

To find the equilibrium constant, you divide the forward rate constant by the reverse rate constant, which will give you 0.676 = K.
by Ryan Lee 1E
Tue Mar 10, 2020 11:20 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework 10
Replies: 11
Views: 125

Re: Homework 10

Section is canceled for sure though, right.
by Ryan Lee 1E
Sat Mar 07, 2020 1:50 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Potential
Replies: 3
Views: 83

Re: Potential

Maximum potential would be the standard E cell potential. The max potential itself means that it is the greatest difference in potential between the anode and the cathode (as the reaction progresses, the cell potential will drop, so max is when the reaction starts). I'm not sure if there's a concret...
by Ryan Lee 1E
Fri Feb 28, 2020 1:57 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Test 2
Replies: 2
Views: 112

Re: Test 2

On the top of the 14B webpage, there's a announcement over what outlines and what will be covered on Test 2. As mentioned, it's just going to be the end of thermochemistry and electrochem.
by Ryan Lee 1E
Fri Feb 28, 2020 1:56 am
Forum: Balancing Redox Reactions
Topic: Redox reactions with single reactant
Replies: 2
Views: 33

Re: Redox reactions with single reactant

Also, these cells have very low potential in comparison to other voltaic cells.
by Ryan Lee 1E
Fri Feb 28, 2020 1:50 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: What's going on at this anode?
Replies: 2
Views: 36

Re: What's going on at this anode?

I'm not entirely sure what is going on with the oxygen and the hydrogen, but I think the platinum in the diagram indicates that the electrode is made of platinum metal.
by Ryan Lee 1E
Fri Feb 28, 2020 1:49 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Non-Standard Potential
Replies: 3
Views: 63

Re: Non-Standard Potential

Assuming you're given all other values necessary/can find them easily, it would simply be plugging in those values and doing the algebra. You can isolate lnQ to one side and everything else on the other side and solve for Q. That answer will then be either greater or less than one.
by Ryan Lee 1E
Fri Feb 28, 2020 1:46 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibbs Free Energy
Replies: 2
Views: 39

Re: Gibbs Free Energy

From an equations perspective, a -E means the equation -nFE will produce a positive number, which means that it's not spontaneous since dG > 0. From a more conceptual perspective, a negative cell potential means that there is negative electron flow from the labeled anode to labeled cathode, or rathe...
by Ryan Lee 1E
Thu Feb 20, 2020 10:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potential
Replies: 3
Views: 40

Re: Cell Potential

Depending on which strategy you use, you will either switch the sign or not. If you flip the half reaction then you will have to multiply by -1, but if you are doing the cathode - anode strategy, then you should not switch the sign since the subtraction will account for the negative sign already.
by Ryan Lee 1E
Thu Feb 20, 2020 10:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E cell values
Replies: 3
Views: 40

Re: E cell values

At that point, doesn't that just mean then you can relabel the cathode and anode. To my knowledge, those are just descriptive, which means you can just slap the term cathode on whichever one is actually positive and having the species being reduced.
by Ryan Lee 1E
Thu Feb 20, 2020 10:16 pm
Forum: Balancing Redox Reactions
Topic: Oxidation numbers
Replies: 6
Views: 76

Re: Oxidation numbers

I think H is +1 in oxidation state senses also because it generally will act as the positive cation in ionic elements/have lower electron affinity in a covalent interaction. H2 is diatomic and as mentioned, is very stable and the electrons are equally shared.
by Ryan Lee 1E
Thu Feb 20, 2020 10:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: calculating E(cell)
Replies: 2
Views: 20

Re: calculating E(cell)

I'd say it's mostly just personal preference. As long as you remember which one requires you to flip the sign and which one has you not flip it, then you should be fine doing either since they both take the same amount of time.
by Ryan Lee 1E
Thu Feb 20, 2020 10:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Half cells
Replies: 2
Views: 24

Re: Half cells

Yep, hydrogen half cells are used as a base measure of voltage difference, and then adding different voltage differences together allow you to compare a half cell that does not contain a hydrogen component.
by Ryan Lee 1E
Mon Feb 10, 2020 9:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Acids
Replies: 3
Views: 30

Re: Polyprotic Acids

Just found a section in the textbook that says that the only polyprotic acid that we would need to calculate the concentrations for the second deprotonation is sulfuric acid. Why do we need to do the same for H3PO4? I just looked back and yeah, you're right. I was looking at the 20L HW and got the ...
by Ryan Lee 1E
Mon Feb 10, 2020 9:45 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: degeneracy W
Replies: 7
Views: 103

Re: degeneracy W

Na is going to be Avogadro's number whereas lowercase n is going to be the number of moles.
by Ryan Lee 1E
Mon Feb 10, 2020 9:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating pH of Weak acid and its salt
Replies: 1
Views: 31

Re: Calculating pH of Weak acid and its salt

Nitrous acid is a weak acid, and KNO2 will dissociate completely in solution because it's a nitrate. This means that the concentration of the NO2 at the beginning will already be the concentration of the KNO2 that has been dissociated. Also, we exclude the K from the equation because we don't care a...
by Ryan Lee 1E
Mon Feb 10, 2020 9:39 pm
Forum: Calculating Work of Expansion
Topic: Lyndon Review Questions #6
Replies: 2
Views: 80

Re: Lyndon Review Questions #6

In this question, you'll need to split the q and w into three separate sections. First the isobaric compression, then the isochoric pressurization, then the isothermal expansion. You can calculate q or w for all of these, which means if you sum the q of all of them, then you'll also know what the w ...
by Ryan Lee 1E
Mon Feb 10, 2020 9:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Acids
Replies: 3
Views: 30

Re: Polyprotic Acids

I think generally, if Ka1 is 10^3 times bigger than Ka2, then you can ignore the second deportation. (you can double check this really quickly for yourself on test if it comes to it) To my knowledge, the most common acid that you will need to calculate the second deportation for is H3PO4.
by Ryan Lee 1E
Mon Feb 10, 2020 9:12 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4F.17
Replies: 1
Views: 24

Re: 4F.17

You can't calculate going straight from 100 C to 85 C since the vaporization of water in the question begins at 85 C. If you were to go straight from 100 C to 85 C and just cool it, then you wouldn't be finding how much it takes to vaporize at 85 C, but only the cooling of the water. On another note...
by Ryan Lee 1E
Mon Feb 10, 2020 9:07 pm
Forum: Calculating Work of Expansion
Topic: Reversible Reactions
Replies: 2
Views: 36

Re: Reversible Reactions

Work is F*d, and here, the F*d is equivalent to P*V. In an irreversible reaction, the pressure instantly drops to a lower value and so the lower value is multiplied by V. In a reversible reaction, the pressure slowly drops, which means that we have to sum all the infinitely small sections of P*V. Th...
by Ryan Lee 1E
Thu Feb 06, 2020 1:48 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: calculating entropy of irreversible and reversible expansion reactions
Replies: 1
Views: 34

Re: calculating entropy of irreversible and reversible expansion reactions

I'm not sure about entropy changes in direct relation with reversible and irreversible reactions, but I know that under certain conditions, you can use the equations of nRln(v2/v1) and nCln(T2/T1) to calculate entropy change. These equations were from wednesday's lecture, and they're derived either ...
by Ryan Lee 1E
Thu Feb 06, 2020 1:38 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: connecting the boltzmann and macro/thermodynamic entropies?
Replies: 1
Views: 19

Re: connecting the boltzmann and macro/thermodynamic entropies?

The boltzman equation at its base is to describe the entropy of a single molecule using its degeneracy of W. But, we usually deal with molecules in the quantity of moles, which means the equation of just Kb*ln(w) is not very useful to us. So, in order to find the entropy of one mole of molecules, we...
by Ryan Lee 1E
Thu Feb 06, 2020 1:26 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: ∆U When ∆T = 0
Replies: 5
Views: 111

Re: ∆U When ∆T = 0

I think from the context of class, we are referring to an isothermal expansion of an ideal gas. This means that the gas is expanding reversibly and work is being done to move the piston and increase the volume. In this case, the work being done would be negative. However, in the isothermal reaction ...
by Ryan Lee 1E
Thu Feb 06, 2020 1:21 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Entropy V.S Enthalpy QUestion
Replies: 3
Views: 69

Re: Entropy V.S Enthalpy QUestion

Spontaneity would be determined by free energy, whose equation is deltaG = deltaH - TdeltaS. It's not just if enthalpy (H) or entropy (S) is a certain value, but the both in combination would have to work together to make something spontaneous. On that note, a positive deltaS indicates that entropy ...
by Ryan Lee 1E
Mon Feb 03, 2020 1:53 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reaction
Replies: 6
Views: 140

Re: Reversible Reaction

In addition, when solving problems involving a reversible reaction, you'll want to make sure to use the work = nRT*ln(v2/v1) equation since you'll actually need to use the integral when the pressure is constantly changing.
by Ryan Lee 1E
Mon Jan 27, 2020 10:22 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: delta U
Replies: 4
Views: 40

Re: delta U

I think we might be going over this stuff in class later in the week.
by Ryan Lee 1E
Mon Jan 27, 2020 10:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: unknown constant
Replies: 3
Views: 24

Re: unknown constant

I believe there should be a table of constants somewhere in the reading, but it's not linked by the problem.
by Ryan Lee 1E
Mon Jan 27, 2020 9:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 11
Views: 134

Re: Hess's Law

Essentially, you'll be given multiple reactions and their enthalpy changes. You can then add those reactions in a sense or flip them so that parts of the left and right side cancel out. You will eventually end up with the equation you are asked to solve. You then add the manipulated enthalpy changes...
by Ryan Lee 1E
Mon Jan 27, 2020 9:32 pm
Forum: Phase Changes & Related Calculations
Topic: Combustion
Replies: 5
Views: 46

Re: Combustion

Also, you should be careful to note the context of "oxidizing." It can be used in terms of a redox reaction, in which case, something being oxidized means it's losing electrons and gaining positive charge.
by Ryan Lee 1E
Mon Jan 27, 2020 9:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of formation
Replies: 6
Views: 50

Re: Standard enthalpy of formation

Yeah, as people have said, diatomic molecules are the in their most stable form, which means that under normal conditions, they already exist in this state. Therefore, it doesn't require additional energy to form them.
by Ryan Lee 1E
Mon Jan 27, 2020 9:19 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 3
Views: 25

Re: Calorimeter

For instance, in a simple calorimeter, the system would be the reaction itself and the surroundings would be the water. The water is the surrounding that absorbs the heat of the reaction.
by Ryan Lee 1E
Tue Jan 21, 2020 12:07 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc to Kp conversion
Replies: 2
Views: 21

Re: Kc to Kp conversion

It's also worth noting from this equation that this will mean Kc = Kp when there are equal moles of reactants and products.
by Ryan Lee 1E
Mon Jan 20, 2020 10:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When and when not to use "P"
Replies: 1
Views: 18

Re: When and when not to use "P"

Yes, in the context of equilibrium, the P represents the pressure, and will only be used when talking about gasses.
by Ryan Lee 1E
Mon Jan 20, 2020 10:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent Ionization
Replies: 4
Views: 30

Re: Percent Ionization

I think it would be the H30+ since that measures the actual amount of H+ that comes away from the acid.
by Ryan Lee 1E
Mon Jan 20, 2020 10:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6E3
Replies: 1
Views: 33

Re: 6E3

The textbook is kind of unclear on the justification, but it seems that when the second deprotonation does not affect the pH significantly, it can be ignored. The most clear passage I could find the book is this: "Except for sulfuric acid (and a few other rare cases), to calculate the pH of a p...
by Ryan Lee 1E
Mon Jan 20, 2020 10:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw change
Replies: 1
Views: 22

Re: Kw change

Kw is the K constant for the reaction 2 H2O <--> H3O+ + OH-. If you add another species to water, Kw stays constant since that other species won't be involved in that reaction. The reaction only has hydroxide ion, hydronium ion, and water. Kw is 1.0 *10^-14 at 25 degrees C if I recall correctly, but...
by Ryan Lee 1E
Mon Jan 20, 2020 10:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Summary of Le Chatelier
Replies: 5
Views: 40

Re: Summary of Le Chatelier

In addition, note that K will only change with temperature, which means adding additional product/reactant or changing pressure does not change K. If product/reactant is added or pressure is changed, you can simply calculate Q and then find what way the reaction will proceed by comparing Q to K.
by Ryan Lee 1E
Thu Jan 16, 2020 3:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.5 d
Replies: 3
Views: 41

Re: 5J.5 d

Adding an inert gas without compressing the container does not change the partial pressure of the original gasses, which is why the Q value doesn't change and thus the equation doesn't shift. In the question, it states that there is a change in total pressure that results from compression, in which ...
by Ryan Lee 1E
Thu Jan 16, 2020 3:50 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas
Replies: 7
Views: 55

Re: Inert Gas

Inert gasses usually don't react, and I think the noble gas group is inert gasses. There are probably other inert gasses but I believe it would tell you if that's so.
by Ryan Lee 1E
Tue Jan 14, 2020 1:33 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A.19
Replies: 6
Views: 82

Re: 6A.19

I got a 10^-15 value as well. Seems the solutions manual is off.
by Ryan Lee 1E
Mon Jan 13, 2020 11:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.39
Replies: 4
Views: 85

Re: 5.39

The equals sign in that image doesn't mean the direct translation from x to 1. Instead, it's 1/6.1*10^-3 because the table in 5G.2 shows the reverse reaction's Kc. So, in order to get the question's Kc, you need to take the reciprocal of the Kc which is just 1/(6.1*10^-3). In terms of the 10^23 term...
by Ryan Lee 1E
Mon Jan 13, 2020 11:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5J.5
Replies: 4
Views: 39

Re: 5J.5

I agree with you that it seems the 2 H2 molecules were just omitted for some reason.
by Ryan Lee 1E
Thu Jan 09, 2020 12:49 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K being small or large
Replies: 4
Views: 33

Re: K being small or large

If K is small, that means the value in the denominator is large and so there is a higher concentration of reactants than products. If K is large, there is a higher concentration of products than reactants.
by Ryan Lee 1E
Wed Jan 08, 2020 9:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Multiples of Chemical Equation
Replies: 3
Views: 34

Re: Multiples of Chemical Equation

I assume that it would work, since when you multiply by two and write the new Kc expression, it's just the same thing as the original Kc expression but raised to the power of what it's multiplied through by. For example, Br2 + 3F2 <--> 2BrF3 has K of (BrF3^2)/(Br2*F2^3). With 2Br + 6F2 <--> 4BrF3, K...
by Ryan Lee 1E
Wed Jan 08, 2020 12:47 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Example in 5I.3
Replies: 1
Views: 12

Example in 5I.3

In the example for 5I.3, it gives us that there are 0.482 mol N2 and 0.933 mol O2 in a reaction vessel of volume 10L. It then gives us K as being 3.2*10^-28. In the example, they solve it by finding the partial pressures of the N2 and O2 and then using an ICE table with the given K value as Kp. Why ...
by Ryan Lee 1E
Tue Jan 07, 2020 11:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3
Replies: 2
Views: 24

Re: 5H.3

I think this question is referring to the idea from section 5H.2 (composite equations). The two equations from Table 5G.2 you would use are the first one (formation of HCl) and fourth one (decomposition of BrCl), and you would multiply the two K values together. K at 300K for HCl is 4.0 * 10^31 and ...
by Ryan Lee 1E
Tue Jan 07, 2020 10:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook example 5H.1
Replies: 2
Views: 28

Re: Textbook example 5H.1

The value of R in this example is a version of the gas constant. Last quarter it was generally 0.0821 (L*atm)/(K*mol), but with the units given in the problem, it's something different. I searched up a list of gas constants and looked for the right units, but I assume it would be given on a test.

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