Search found 56 matches
- Sun Mar 15, 2020 2:10 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic and voltaic cells
- Replies: 5
- Views: 428
Re: Galvanic and voltaic cells
The opposite of a galvanic cell is an electrolytic cell. Galvanic cell is spontaneous which electrolysis is not.
- Sun Mar 15, 2020 2:04 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 4
- Views: 488
Re: oxidation numbers
There are some basic ones that you'll just have to remember:
hydrogen is +1 when bound to nonmetal but is -1 when bound to a metal
oxygen in the form of O^2 is -1; all other forms are -2
hydrogen is +1 when bound to nonmetal but is -1 when bound to a metal
oxygen in the form of O^2 is -1; all other forms are -2
- Sun Mar 15, 2020 1:59 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells
- Replies: 2
- Views: 298
Re: Concentration Cells
You make the one with the lower concentration the product and figure out if it's oxidation or reduction.
- Sun Mar 15, 2020 1:56 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst K vs Q
- Replies: 14
- Views: 991
Re: Nernst K vs Q
The major difference between the two is if the rxn is at equilibrium or not. If you use K, then you are taking into consideration that the rxn is at equilibrium. If a rxn is at equilibrium, certain factors would be affected like E.
- Sun Mar 15, 2020 1:52 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: lnQ
- Replies: 22
- Views: 1420
Re: lnQ
Yes, you would still apply the coefficients as the power.
- Sun Mar 15, 2020 1:46 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: spontaneity
- Replies: 4
- Views: 494
Re: spontaneity
When delta g is negative, it is saying that there is available energy for the reaction to happen. So it is spontaneous.
- Sun Mar 08, 2020 10:17 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Intermediate Species
- Replies: 9
- Views: 717
Re: Intermediate Species
It is a specie that first gets produced and then later used as a reactant.
- Sun Mar 08, 2020 10:05 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 8
- Views: 514
Re: Catalysts
They somehow affect the orientation of the substrate it binds to, helping it to achieve the proper orientation.
- Sun Mar 08, 2020 9:58 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Pre Equillibrium
- Replies: 2
- Views: 273
Re: Pre Equillibrium
As a forward rxn is happening, the products are accumulating. Since thee are so many products, the rxn also wants to reverse the direction to try to get rid of the products (I am not sure if the rxn actually reverses the direction or it is just a state it wants to achieve). Therefore, this whole sit...
- Wed Mar 04, 2020 3:44 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Strongly Reducing vs Oxidizing
- Replies: 2
- Views: 194
Re: Strongly Reducing vs Oxidizing
Reducing agents refer to the substance being oxidized. If the problem gives you several different reduction rxns, you have to do a little inverse thinking. The more positive the standard reduction potential is, the more likely that rxn will happen. However, that rxn is a reduction rxn. If reduction ...
- Wed Mar 04, 2020 3:29 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Figuring out n
- Replies: 15
- Views: 972
Re: Figuring out n
Write out half rxns
Balance half rxns
Combine the two half rxns (when combining the two rxns, you should be canceling out electrons. The number of electrons, do not add up the number of electrons from both rxns, is your n).
Balance half rxns
Combine the two half rxns (when combining the two rxns, you should be canceling out electrons. The number of electrons, do not add up the number of electrons from both rxns, is your n).
- Wed Mar 04, 2020 3:20 pm
- Forum: Balancing Redox Reactions
- Topic: Both Oxidizing and Reducing Agent
- Replies: 4
- Views: 407
Re: Both Oxidizing and Reducing Agent
If the species was reduced, then it is the oxidizing reagent, and if it was oxidized, it is the reducing reagent.
Think of them as the opposite.
Think of them as the opposite.
- Mon Mar 02, 2020 12:17 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 10
- Views: 641
Re: Nernst
E = Eo -(RT/nF) ln Q
There are also other equations you can derive from this equation that can be considered as the Nernst equation.
There are also other equations you can derive from this equation that can be considered as the Nernst equation.
- Mon Mar 02, 2020 12:08 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Free Energy and Cell Potential Relationship
- Replies: 3
- Views: 283
Re: Free Energy and Cell Potential Relationship
When you're given the value of delta G or cell potential and are asked to find the other, you can use the equation mentioned in the previous comment.
- Mon Mar 02, 2020 12:04 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Reduced/Oxidized based on Ecell
- Replies: 6
- Views: 460
Re: Reduced/Oxidized based on Ecell
Maybe you can look at the oxidation numbers.
- Mon Mar 02, 2020 12:01 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Value of K
- Replies: 2
- Views: 212
Re: Value of K
My TA said that if E knot is positive, k is greater than 1 and when E knot is negative, k is less than 1. But I don't know if k would equal to 0 is E knot is 0.
- Sun Mar 01, 2020 11:53 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst equation and K
- Replies: 3
- Views: 323
Re: Nernst equation and K
K represents the reaction is at equilibrium.
- Sun Feb 23, 2020 12:44 pm
- Forum: Balancing Redox Reactions
- Topic: Steps to Balance a Basic Solution
- Replies: 2
- Views: 228
Re: Steps to Balance a Basic Solution
In basic solution: 1. Identify what is being reduced and oxidized 2.Balance half-reactions by: a. balance elements other than oxygen and hydrogen b. balance the oxygens by adding H2O c. balance the hydrogens by adding H+ d. cancel H+ by adding OH- e. balance the charge of each reaction by adding ele...
- Sun Feb 23, 2020 12:37 pm
- Forum: Balancing Redox Reactions
- Topic: Redox in Acidic/Basic Solutions
- Replies: 3
- Views: 272
Re: Redox in Acidic/Basic Solutions
The only difference when balancing a redox reaction in a basic solution compared to an acidic solution is that in basic solution, you would have to do the extra step of canceling the H+ with the OH- at the end (everything else is the same).
- Sun Feb 23, 2020 12:27 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number of H
- Replies: 6
- Views: 486
Re: Oxidation number of H
I was taught that if hydrogen is bound to a metal, it's -1; if bound to a nonmetal, it's +1.
- Sun Feb 23, 2020 12:26 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation States
- Replies: 7
- Views: 415
Re: Oxidation States
Hydrogens are +1 if bound to nonmetals or -1 if bound to metals.
If oxygen is seen as peroxide (O2), then it's -1; if in any other compounds, it's -2
If oxygen is seen as peroxide (O2), then it's -1; if in any other compounds, it's -2
- Sun Feb 23, 2020 12:21 pm
- Forum: Balancing Redox Reactions
- Topic: What is Being Reduced?
- Replies: 10
- Views: 581
Re: What is Being Reduced?
It might be better to include Fe3+ is being reduced to Fe2+, just to show that you know which iron is being reduced. In addition, some problems specifically ask you to include which species is reduced or oxidized and from what oxidation number to what.
- Sun Feb 16, 2020 2:18 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: 3/2R & 5/2R
- Replies: 9
- Views: 747
Re: 3/2R & 5/2R
mcat/ncat also incorporates Cv and Cp sometimes.
- Fri Feb 14, 2020 4:54 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal Reversible
- Replies: 6
- Views: 396
Re: Isothermal Reversible
I remember a UA mentioned that isothermal is always reversible but reversible does not always mean isothermal; I think that is what he said.
- Fri Feb 14, 2020 4:50 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: State functions
- Replies: 5
- Views: 272
Re: State functions
Rather than remembering all the state functions, just remember which ones are not because there are fewer of them. Heat and work are not state functions while the rest are. For intensive/ extensive properties, it might be easier to remember the definition of each rather than remembering all the exam...
- Sun Feb 09, 2020 11:41 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Microstates
- Replies: 6
- Views: 266
Re: Microstates
A microstate is the possible arrangements of the molecule.
- Sun Feb 09, 2020 11:38 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy equation
- Replies: 2
- Views: 107
Re: Entropy equation
You use this equation if only heat and temperature are given in the problem. If you do not have enough information to solve for entropy with the other equations involving constant pressure, temperature, or volume, this might be the one to use.
- Sun Feb 09, 2020 11:35 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Constant T,P,V
- Replies: 4
- Views: 184
Re: Constant T,P,V
A good strategy is to write out the given values, like what is volume1 and volume2. Usually, if there is only one temperature or volume or pressure, you will know that that is the one staying constant.
- Sun Feb 09, 2020 11:32 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Important conditions
- Replies: 3
- Views: 167
Re: Important conditions
I think it's also good to know about reversible and irreversible reactions, and how to differentiate between the two.
- Sun Feb 09, 2020 11:28 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Intensive vs. extensive, state vs. non state
- Replies: 6
- Views: 262
Re: Intensive vs. extensive, state vs. non state
I am not sure what you mean by intensive vs. extensive states but if you are referring to the intensive and extensive properties, they are:
Intensive
color, temperature, texture, density
Extensive
mass/weight, length, volume
Intensive
color, temperature, texture, density
Extensive
mass/weight, length, volume
- Sat Feb 08, 2020 9:23 am
- Forum: Phase Changes & Related Calculations
- Topic: General Phase Change Calculations
- Replies: 6
- Views: 364
Re: General Phase Change Calculations
There are important differences between the two situations. One has a temperature change while the other one has a constant temperature. Therefore, the equations need to take these differences into consideration, resulting in different equations.
- Sat Feb 08, 2020 9:04 am
- Forum: Calculating Work of Expansion
- Topic: Irreversible Expansion Explained
- Replies: 7
- Views: 415
Re: Irreversible Expansion Explained
Adding on to the balloon analogy, for me, reversible is slowly blowing air into the balloon so it "expands" or releasing air so it "compresses;" it can go both ways. Irreversible, on the other hand, is blowing the balloon so fast that it pops, so there is no way of going back.
- Sun Feb 02, 2020 10:16 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Extensive/Intensive Property
- Replies: 4
- Views: 93
Re: Extensive/Intensive Property
An intensive property is not dependent on the amount of a substance, like color and temperature. The extensive property, on the other hand, is dependent on the amount of a substance, like weight.
- Sun Feb 02, 2020 9:58 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: When to leave out reactants/products from enthalpy calculations
- Replies: 4
- Views: 163
Re: When to leave out reactants/products from enthalpy calculations
To add on, the most stable forms won't affect enthalpy change only when calculating the enthalpy of formation.
- Sun Feb 02, 2020 9:56 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law vs Bond Enthalpies vs Standard Enthalpies of Formation
- Replies: 7
- Views: 299
Re: Hess's Law vs Bond Enthalpies vs Standard Enthalpies of Formation
Usually, they will explicitly say to use bond enthalpy or standard enthalpy of formation in the problem. Bond enthalpies usually give you a chart with the different bond and their enthalpy values.
- Wed Jan 29, 2020 3:37 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve for Water - Steam
- Replies: 2
- Views: 115
Re: Heating Curve for Water - Steam
Yes, you are correct. Phase change requires a lot of energy in the form of heat, that energy is so great that when it is released (touches skin), it causes severe burns.
- Wed Jan 29, 2020 3:26 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4A.9
- Replies: 4
- Views: 164
Re: 4A.9
Your change in temperature for copper should be final temperature-100, not the other way around.
- Wed Jan 29, 2020 3:06 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Closed Systems
- Replies: 13
- Views: 718
Re: Closed Systems
Yes, you are right. For the volume specifically, you are either doing work on the system or the system is doing work on the surrounding.
- Wed Jan 22, 2020 4:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6E.1
- Replies: 1
- Views: 133
Re: 6E.1
Since it's aqueous, it's reacting with water. Set up the reaction as HSO4 + H2O double arrow H3O + SO4^2-. Find [H3O+] with an ICE table, then take the -log of the concentration to get the pH.
- Wed Jan 22, 2020 4:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acids and Bases pka and pkb
- Replies: 8
- Views: 334
Re: Acids and Bases pka and pkb
The lower the pKb, the stronger the base. The lower the pKa, the stronger the acid.
- Wed Jan 22, 2020 3:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6D 13
- Replies: 1
- Views: 183
Re: 6D 13
I believe you will have to use the table they gave to you for the value of k. Then set up the ice table with your reaction. Since these compounds are aqueous, they are reacting with water. After you have found the [OH-] or[H+], take the -log of the concentration to get pH or pOH. After you have foun...
- Wed Jan 22, 2020 3:37 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5J 5: increase in pressure
- Replies: 4
- Views: 174
Re: 5J 5: increase in pressure
For B): First, you would not take solids into consideration when adding up the coefficients on each side. H2O has one mole on the reactants side. H2 and CO each have 1 mole on the products side; together, it's two moles. Since pressure increases, the volume decreases, meaning it will favor the side ...
- Wed Jan 22, 2020 3:31 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Buffers
- Replies: 3
- Views: 218
Re: Buffers
He said that buffers help resist change. Our body is only equipped to function under a limited range of conditions. The buffers help our mechanisms stay in that optimal range.
- Wed Jan 22, 2020 3:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Conjugate Seesaw
- Replies: 3
- Views: 189
Re: Conjugate Seesaw
The conjugate seesaw is referring to the conjugate acid and conjugate base of acid and base, the compound a base or acid turns into after donating or accepting hydrogen. A problem can give you the concentration of a conj. base or acid and some other information and ask you to use that information to...
- Sun Jan 19, 2020 9:15 am
- Forum: Ideal Gases
- Topic: R constant in Ideal Gas Law
- Replies: 4
- Views: 140
Re: R constant in Ideal Gas Law
When you plug in all the variables in the pv=nRT equation, you want to make sure all the units cancel out. The correct unit should give you only moles or some kind of pressure unit at the end (after the cancellation of units).
- Sun Jan 19, 2020 9:12 am
- Forum: Ideal Gases
- Topic: Ideal gas law and [P]/[R]
- Replies: 3
- Views: 141
Re: Ideal gas law and [P]/[R]
You can also us pv=nRT when concerting from concentration to pressure; it goes both ways.
- Wed Jan 15, 2020 3:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Conjugate Seesaw and Kw
- Replies: 3
- Views: 131
Re: Conjugate Seesaw and Kw
Rather than thinking everything is about Kw, why not try thinking that it's all these useful information we can get out of Kw. We can know about Ka/Kb, [H30]/[OH], or even the pH/pOH of an acid/base. In a way, all these values are connected. Kw=Ka x Kb and Ka and Kb connects back to the [H30] and [O...
- Wed Jan 15, 2020 12:00 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K units
- Replies: 10
- Views: 519
Re: K units
Explaining in a non-chemistry way, K is the ratio of products over reactants. And ratios are just numbers; they don't have units.
- Tue Jan 14, 2020 11:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5H.2
- Replies: 2
- Views: 112
Re: 5H.2
My solution manual only includes answers for odd problems, so I don't know how to explain the 2.5 * 10^7. Plus, there were three reactions to the problem, which one were you talking about? But the problem is connecting back to the topics that if a reaction is reversed, then the K would be the invers...
- Tue Jan 14, 2020 11:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acids and Bases
- Replies: 3
- Views: 127
Re: Acids and Bases
I remember Lavelle saying that when one concentration increases, the other concentration decreases (but didn't catch why). So when you multiply the two, they still give you 1.0 x 10^-14. In addition, the concentration affects the intensity of the reaction happening, not the ratio of products over re...
- Sat Jan 11, 2020 10:49 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Significant Figures
- Replies: 8
- Views: 409
Re: Significant Figures
I would say consider both the K constant and initial concentrations because you used both pieces of information in order to figure your answer. Sig figs are determined by all the numbers you used in a problem.
- Sat Jan 11, 2020 10:46 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Q
- Replies: 10
- Views: 544
Re: K vs. Q
Yup, like everybody else has said, K is for when you know that the reaction is in equilibrium and Q is when you are not sure if the reaction is in equilibrium.
- Sat Jan 11, 2020 10:33 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook question 5I.15
- Replies: 1
- Views: 90
Re: Textbook question 5I.15
Use the equilibrium constant K =[P]/[R] to find the [NH3]. Since NH4HS is a solid, we wouldn't include it in the equation as [R]. The [NH3] is .400/2.0 which is 0.2. Then you plug in the numbers: (1.6 x10^-4) = .2([H2S]). Therefore, the [H2S] is 8 x 10^4.
- Sat Jan 11, 2020 9:57 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Hw 5I.1
- Replies: 4
- Views: 221
Re: Hw 5I.1
Technically, you can use the ICE table for this problem, but it will take more time and work. ICE tables provides other information like the change in concentrations due to the process of the reaction.
- Sat Jan 11, 2020 9:52 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G1
- Replies: 2
- Views: 113
Re: 5G1
I wouldn't recommend using equilibrium reaction and constant interchangeably in this case because one is the reaction itself and the other is the ration of products and reactants. Like Jacey said, the constant is [P]/[R}, which depends on the equation. The equilibrium equation would be affected by t...
- Sat Jan 11, 2020 9:44 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Knowing it's an Equilibrium Reaction
- Replies: 4
- Views: 226
Re: Knowing it's an Equilibrium Reaction
I think that the double arrow is the only way to recognize an equilibrium equation, unless otherwise specified in the problem. Another characteristic of equilibrium equations is that their concentrations have to remain constant.