Search found 62 matches
- Sat Mar 14, 2020 10:09 pm
- Forum: Van't Hoff Equation
- Topic: ln
- Replies: 34
- Views: 1782
Re: ln
In the same way, raising logx to 10 will cancel the log because standard log is base 10 (log10x). Ln is loge(x).
- Sat Mar 14, 2020 10:06 pm
- Forum: Experimental Details
- Topic: Data
- Replies: 5
- Views: 538
Re: Data
it doesnt matter which order you do, as long as you can isolate an exponent x or y to get the respective rxn order. The numbers of one of the reactants in both trials should cancel out. So, as long as the variable placements are consistent it doesn't matter, right? Or is the placement not a factor ...
- Sat Mar 14, 2020 10:05 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: A
- Replies: 2
- Views: 303
A
For the Arrhenius Equation, why is A approximately = 1 in most cases in this class?
- Sat Mar 14, 2020 10:03 pm
- Forum: Balancing Redox Reactions
- Topic: flipping equations
- Replies: 7
- Views: 553
Re: flipping equations
This is all based on the equation that Ecell = Eright - Eleft and as Eleft is the oxidation cell, you 'flip' the oxidation cell.
- Sat Mar 14, 2020 10:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam Time
- Replies: 13
- Views: 889
Re: Final Exam Time
Even if CCLE crashes (again oof), though, the test saves every 2 minutes so we'll be good!
- Sat Mar 14, 2020 10:01 pm
- Forum: General Rate Laws
- Topic: Factors Affecting k
- Replies: 83
- Views: 4537
Re: Factors Affecting k
Vinita Saxena 2I wrote:Yes, it can change if the temperature changes, that is the only way it can change
Isn't the addition of a catalyst also a way to change it?
- Tue Mar 10, 2020 6:00 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Email Announcement
- Replies: 8
- Views: 673
Email Announcement
What does Gene Block’s announcement mean for our final in this class as gatherings of more than 100 people?
- Mon Mar 09, 2020 1:16 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: k constants
- Replies: 1
- Views: 107
Re: k constants
And also then why does k = 2k2?
- Mon Mar 09, 2020 1:15 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: k constants
- Replies: 1
- Views: 107
k constants
Why is 2k1k2 / k’1 equal to k (of observed rate law)? Why do these agree with one another?
- Wed Mar 04, 2020 1:54 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Figuring out n
- Replies: 15
- Views: 925
Re: Figuring out n
n is the mols of electrons transferred! Make sure not to find a common multiple, then, for example if for a reduction 2 electrons are transferred whereas for an oxidation 3 electrons are transferred -> common multiple 6 when balancing equations and 6 electrons are transferred; (n=6).
- Wed Mar 04, 2020 1:52 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: calculating K2?
- Replies: 3
- Views: 601
Re: calculating K2?
You find K2 by using the Vant Hoff equation you wrote down: ln K2/K1=-ΔH°/R [1/T2-1/T1] After finding K2, square root it to find the H3O+ concentration. Use the concentration to find the pH. This pH is the neutral pH at 10 degrees C. Compare that number with 7 to see if a pH of 7 is acidic or basic...
- Wed Mar 04, 2020 1:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: When to use Platinum as an electrode
- Replies: 4
- Views: 329
Re: When to use Platinum as an electrode
If your reaction involves conductive metals like Ag and Cu, though, you do not need to involve Pt as a conductor for your cell diagram.
- Wed Mar 04, 2020 1:46 pm
- Forum: Van't Hoff Equation
- Topic: Converting K back to Kc
- Replies: 5
- Views: 464
Re: Converting K back to Kc
What's the equation needed to convert K back to Kc? I assumed you would just rearrange the Kc to K equation, but I wanted to ask just to be sure. aren't those the same Not according to the book :( Look at the very last part of section 5J.3, it talks about converting K to Kc when using Van't Hoff eq...
- Wed Mar 04, 2020 1:44 pm
- Forum: First Order Reactions
- Topic: Graph
- Replies: 9
- Views: 705
Re: Graph
If you write [A] vs. time for a 1st order run, though, it'll show exponential decay so make sure to have it in ln form!
- Mon Mar 02, 2020 12:43 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.17
- Replies: 1
- Views: 230
6N.17
Why is there work done in this system, and how do we find Ecell? I keep calculating it to be 0V as the cathode and anode are reducing/oxidizing the same reaction in reverse to one another (?)
- Sun Mar 01, 2020 11:40 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in Equation
- Replies: 6
- Views: 436
n in Equation
I'm a bit confused as to how to find n in reactions and I'm a bit confused too with what it represents.
For example,
for the reaction Mn + Ti2+ <--> Mn2+ + Ti n=2, but I'm not sure as to why.
Could someone help explain?
For example,
for the reaction Mn + Ti2+ <--> Mn2+ + Ti n=2, but I'm not sure as to why.
Could someone help explain?
- Fri Feb 28, 2020 12:29 pm
- Forum: General Rate Laws
- Topic: Reaction Rates
- Replies: 5
- Views: 358
Reaction Rates
Why are all reaction rates 'positive' if the [reactants] decreases in exchange to an increase in [products] (for a forward reaction, in example)?
- Fri Feb 28, 2020 12:23 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Heat Death
- Replies: 2
- Views: 412
Heat Death
What does the eventual heat death of the universe say about its entropy and enthalpy relationship? Is all of the energy in the universe in its potential energy form?
- Fri Feb 28, 2020 12:21 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Diamond Reaction
- Replies: 4
- Views: 372
Re: Diamond Reaction
Lavelle said that the reaction from diamond to graphite was spontaneous but had a very high activation energy and would occur very slowly. Does this mean that over time, say a few trillions years, the diamond is slowly collecting enough energy to overcome the energy barrier? Or would the reaction e...
- Fri Feb 28, 2020 12:19 pm
- Forum: Biological Examples
- Topic: ATP example
- Replies: 7
- Views: 3065
Re: ATP example
MariahClark 2F wrote:Wouldn’t the reaction be exergonic since it’s giving off energy and not requiring it?
In ATP's case, yes, but not all hydrolytic reactions are exergonic -- when it requires more energy than it gives off.
- Fri Feb 28, 2020 12:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 10
- Views: 539
Re: Galvanic Cells
Yes, when a battery is dead, the system has reached equilibrium -- though I'm wondering now if it's possible to 'revive' a battery or replace its galvanic cells concentration gradient?
- Fri Feb 21, 2020 1:37 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Spontaneity
- Replies: 7
- Views: 564
Spontaneity
Do higher cell potentials within a cell indicate anything about the rate of the reaction or just the spontaneity?
- Fri Feb 21, 2020 1:14 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrode
- Replies: 4
- Views: 285
Electrode
When Platinum is an electrode, as it is carrying electrons, on an atomic level is it getting reduced and oxidized continuously as electrons are passed from atom to arom
- Fri Feb 21, 2020 12:28 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number of Ozone
- Replies: 10
- Views: 690
Re: Oxidation number of Ozone
If you look at the lewis structure of ozone, it does have individual oxygen formal charges but the overall formal charge is 0 and there is resonance; the oxidation number of the whole molecule of ozone (not of the individual oxygen atoms that compose it) is thus 0.
- Fri Feb 21, 2020 12:25 pm
- Forum: Balancing Redox Reactions
- Topic: Redox Proton Transfer
- Replies: 3
- Views: 185
Redox Proton Transfer
Will we ever examine proton transfer in redox reactions and how that is linked to electron transfer, as that bit has confused me in bio classes?
- Fri Feb 21, 2020 12:24 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation numbers
- Replies: 6
- Views: 412
Re: Oxidation numbers
Kate Swertfager wrote:Are all diatomic molecules neutral charge?
Diatomic molecules of the same atom (homonuclear) should all be neutral charge.
- Fri Feb 21, 2020 12:22 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Favorability [ENDORSED]
- Replies: 1
- Views: 177
Favorability [ENDORSED]
If you have three galvanic cells all linked individually with the other two, will the two with the most favorable change in Voltage react together or would there be a system mixed reaction(s)?
- Fri Feb 21, 2020 12:19 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Voltage and Current
- Replies: 2
- Views: 145
Voltage and Current
How are Voltage and Current related? Will we ever see an ammeter included in diagrams in this class -- will we relate amperes and volts in an equation?
- Sun Feb 16, 2020 11:53 am
- Forum: Van't Hoff Equation
- Topic: concept help
- Replies: 4
- Views: 247
Re: concept help
Van't Hoff relates a reaction's equilibrium constant Keq with temperature, standard enthalpy, and standard entropy -- so it'd be useful in modeling how the equilibrium constant changes due to T, S, and H changes I assume in a more definite way. [url]https://en.wikipedia.org/wiki/Van_%27t_Hoff_equati...
- Sun Feb 16, 2020 11:46 am
- Forum: Balancing Redox Reactions
- Topic: skeletal equations
- Replies: 3
- Views: 187
Re: skeletal equations
I think it just has to do with the ways to write an equation: C is usually put at the center as it is a central atom within this compound, but the more electropositive atom is usually put at the right (C) and the more electronegative at the left (O). Those conditions conflict here, so both ways of w...
- Sun Feb 16, 2020 11:43 am
- Forum: Balancing Redox Reactions
- Topic: oxidation vs reduction
- Replies: 19
- Views: 926
Re: oxidation vs reduction
Veronica Lu 2H wrote:Leo goes Ger [censored]
Losing electrons = oxidation
Gaining electrons= reduction
Similarly, OIL RIG helps me:
Oxidation is Loss
Reduction is Gain
- Sun Feb 16, 2020 11:42 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm Curve
- Replies: 45
- Views: 2127
Re: Midterm Curve
Going off what happened in 14A and in his syllabus, he does not curve the midterm but a 50% in the class is a C, so in that way he does curve the final grade to help those that are close to failing. Does this mean all other grades are curved too? Like how low does an A or an A- go? Or does it not a...
- Sun Feb 16, 2020 11:41 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free energy concept
- Replies: 16
- Views: 786
Re: Gibbs Free energy concept
The Gibbs free energy can predict the spontaneity of a reaction at different circumstances / environmental conditions. In this way, it can predict at what temperature -- for example -- a reaction becomes spontaneous if all other factors are constant.
- Fri Feb 07, 2020 12:25 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm Equations
- Replies: 4
- Views: 266
Midterm Equations
Should we familiarize ourselves but not memorize the equations in thermodynamics for the midterm? Or should we focus on memorizing some of them too -- ones that won't be provided on an equation sheet?
- Fri Feb 07, 2020 12:24 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Entropy
- Replies: 4
- Views: 162
Re: Entropy
The more material there is capable of increasing disorder, the higher the entropy potential exists.
- Fri Feb 07, 2020 12:22 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: state occupation of phases
- Replies: 7
- Views: 265
Re: state occupation of phases
Gas molecules are higher energy and occupy the entirety of the volume of a container as they 'bounce' off of one another and off of the container; it has a lot to do with the decreased density and the increased speed of the particles when they're in their gaseous phase.
- Fri Feb 07, 2020 12:18 pm
- Forum: Calculating Work of Expansion
- Topic: Difference in Wirr and Wrev
- Replies: 4
- Views: 222
Re: Difference in Wirr and Wrev
Wrev is an ideal situation with constant Temperature; Wirr is the more realistic and non-constant Temperature scenario and thus it does less work.
- Mon Feb 03, 2020 1:42 pm
- Forum: Calculating Work of Expansion
- Topic: Degeneracy and Volume
- Replies: 6
- Views: 149
Degeneracy and Volume
Is W2/W1 always equal to V2/V1?
- Fri Jan 31, 2020 1:30 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Open vs. Closed Internal Energies
- Replies: 3
- Views: 147
Open vs. Closed Internal Energies
Today, we talked about in class that in an open system with an exothermique rxn there is expansion work being done.
If it was a closed system, is there no expansion work? Though pressure isn’t constant?
If it was a closed system, is there no expansion work? Though pressure isn’t constant?
- Fri Jan 31, 2020 1:00 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Reversible vs Irreversible formula
- Replies: 4
- Views: 165
Re: Reversible vs Irreversible formula
If the problem indicates that the system is under a constant pressure, then you would use the w=-P∆V equation to calculate the work done. If the problem instead indicates that the reaction is an isothermic expansion where pressure is not constant, then you would use the equation for a reversible re...
- Fri Jan 31, 2020 12:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 #5
- Replies: 7
- Views: 291
Re: Test 1 #5
You're given pKb so you can find Kb. However, in the reaction given you need Ka because HF is an acid. Solve for Ka by using Ka*Kb=Kw, K =1*10^-14. Ka is now your equilibrium constant.Then use the given initial concentration of hydrogen fluoride, 0.12M, and complete an ice table using the Ka consta...
- Fri Jan 31, 2020 12:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm
- Replies: 8
- Views: 312
Re: Midterm
Will it focus more on the new content than what we’ve already learned for Test 1 or just even distribution?
- Fri Jan 31, 2020 12:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ideal Gas QUestions
- Replies: 8
- Views: 392
Re: Ideal Gas QUestions
504999222 wrote:If the pressure goes up, would that mean the volume would go down?
Can’t pressure go up with T going up from PV=nRT with no effect on volume?
- Fri Jan 31, 2020 12:42 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed vs isolated systems
- Replies: 24
- Views: 821
Re: Closed vs isolated systems
A bomb calorimeter would be an isolated system; a closed system would be the ‘cup’ with the external pressure image.
- Sun Jan 26, 2020 11:49 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 4B.3
- Replies: 1
- Views: 68
4B.3
This problem involves 982 J = 492 J + w so I calculated the answer to be 490J, but the back of the textbook says its 90 x 10^2 J. Could someone please explain if that's correct?
- Fri Jan 24, 2020 12:33 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka and Kb
- Replies: 10
- Views: 482
Re: Ka and Kb
Bryan Chen 1H wrote:No, strong acids and bases also have Ka and Kb i think, it is just very large (and they also dissociate completely) so there's no real need to use it in problems
What, hypothetically, would be a situation that we use strong acids'/bases' Ka and/or Kb?
- Fri Jan 24, 2020 12:30 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam vs. Boiling Water
- Replies: 10
- Views: 445
Re: Steam vs. Boiling Water
Basically, this is because steam has undergone a phase change from liquid to water vapor (vaporization). Vaporization requires a lot of energy. When steam touches your skin, it will release a lot of energy as it cools to form liquid water. Water, while at the same energy, does not have the same lat...
- Fri Jan 24, 2020 12:27 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Transition Temp.
- Replies: 6
- Views: 323
Phase Transition Temp.
Can someone reiterate how temperature remains constant during a phase transition? Does it then suddenly just spike/fall after the transition is complete? A bit confused just by the process of it all. How is the steam causing burns example applicable?
- Fri Jan 24, 2020 12:25 pm
- Forum: Ionic & Covalent Bonds
- Topic: Carbon
- Replies: 4
- Views: 493
Re: Carbon
The only atoms I can think of capable of making quad bonds are certain transition metals -- 1 s bond, 2 p bonds, and 1 d bond.
- Fri Jan 24, 2020 12:23 pm
- Forum: Ideal Gases
- Topic: Kc vs Kp
- Replies: 109
- Views: 4369
Re: Kc vs Kp
The difference here just has to do with units used, though Kp will include all gases yes.
- Sat Jan 18, 2020 11:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Difference between K and Q?
- Replies: 11
- Views: 516
Re: Difference between K and Q?
K is a fixed value for the reaction, while Q varies if the reaction is/is not yet at equilibrium and we can compare the two values to determine if the reaction is at equilibrium or not.
- Sat Jan 18, 2020 11:29 am
- Forum: General Science Questions
- Topic: Body Reactions
- Replies: 1
- Views: 111
Body Reactions
Since the acid-base equilibria we're exploring right now is dependent on Kw, at 25 degrees Celsius, how different are reactions with organic life such as the human body where regular temperatures are completely different (37 degrees C for human body).
- Sat Jan 18, 2020 11:22 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Quick way
- Replies: 7
- Views: 332
Re: Quick way
The example Dr. Lavelle gave in class was if you added Helium to a reaction occurring within a sealed container. While the pressure of the reaction is increasing, it has no effect on the equilibrium because adding gas doesn't have any effect on the actual concentration of either the products or rea...
- Sat Jan 18, 2020 11:19 am
- Forum: Ideal Gases
- Topic: Topics on Test 1
- Replies: 37
- Views: 1245
Re: Topics on Test 1
At this point, everything we've done in lecture which seems to cover both outline 1 and 2.
- Sat Jan 18, 2020 11:15 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Tips for Test
- Replies: 23
- Views: 1070
Re: Tips for Test
The video modules are available on the class website too and those really helped me over winter break, so use those too to study and review!
- Mon Jan 13, 2020 12:21 pm
- Forum: General Science Questions
- Topic: Salt Dissolving in Water
- Replies: 3
- Views: 321
Re: Salt Dissolving in Water
Tai Metzger 3K wrote:I hope I can help you resolve this haunting question. I believe that it is a physical reaction because no bonds are broken.
I thought, though, that salt dissolving in water meant that the ions bonds were broken -- making the solution homogeneous (?)
- Thu Jan 09, 2020 4:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 513262
Re: Saying Thank You to Dr. Lavelle
Dear Dr. Lavelle,
The quarter just started, but you've already introduced us to so many resources and have made access to help readily available. With all my other classes, this constant makes me so much less stressed.
Thank you so much!
The quarter just started, but you've already introduced us to so many resources and have made access to help readily available. With all my other classes, this constant makes me so much less stressed.
Thank you so much!
- Thu Jan 09, 2020 4:11 pm
- Forum: General Science Questions
- Topic: Salt Dissolving in Water
- Replies: 3
- Views: 321
Salt Dissolving in Water
This is a question that has haunted me for many years: Is salt (NaCl) dissolving in water a physical or chemical change? In water the ions are technically separated as the sheer [H2O] is powerful enough to separate them (the amount of ion-dipole interactions is more and stronger than the ionic bonds...
- Thu Jan 09, 2020 4:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.57
- Replies: 1
- Views: 100
5.57
For 5.57 of the Focus 5 Exercises, does anyone know how to complete the last part about finding the [NO]? We're given the initial [] of one reactant and the equilibrium [] of one product, but there's 2 reactants and 2 products and that's two unknowns.
- Thu Jan 09, 2020 4:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.39
- Replies: 1
- Views: 88
5.39
5.39 on the Focus 5 Exercises involves Table E.2, but I can't seem to find that table in my textbook. Does anyone else have this problem?
- Thu Jan 09, 2020 3:59 pm
- Forum: Ideal Gases
- Topic: K value
- Replies: 14
- Views: 1087
Re: K value
It's also important to remember that the significance of K is only considered strong when it is either >10^3 (strongly favor products) or <10^-3 (strongly favor reactants). Anything in between those two values still favors one side or the other (except for the rare circumstance at 1), but isn't cons...
- Mon Jan 06, 2020 10:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5I.23
- Replies: 1
- Views: 88
5I.23
Has anyone solved 5I.23? It involves CO(g) + 3H2(g) -><- CH4(g) + H2O(g) and we know the initial [] of CO is 0.2 mol/L and H2 is 0.3 mol/L (the products are 0) and that [CH4] at equilibrium is 0.478, but we don't know anything about [H2O] at equilibrium. How do we solve for Kc with that unknown? I t...