## Search found 58 matches

Mon Mar 19, 2018 12:12 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation
Replies: 2
Views: 385

### Re: Arrhenius equation

no, as long as your T1 and k1 are corresponding
Sun Mar 18, 2018 10:27 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: S and pressure
Replies: 3
Views: 397

### Re: S and pressure

I'm assuming it will increase but I'm not 100% sure
Sun Mar 18, 2018 10:25 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: mechanism differentiation
Replies: 2
Views: 256

### Re: mechanism differentiation

if the slow step is the first step, I don't know if you still have to keep track of intermediates?
Sun Mar 18, 2018 10:21 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: metal dissolved
Replies: 2
Views: 243

### Re: metal dissolved

does that mean spontaneous solutions in general will have metals dissolve in the solution?
Mon Mar 12, 2018 8:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Given information
Replies: 5
Views: 261

### Re: Given information

The reaction with the higher activation energy is the slow reaction, I'm not 100% sure, but if he doesn't explicitly say which is fast and which is slow I think that should be helpful as well.
Mon Mar 12, 2018 3:19 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.61
Replies: 4
Views: 223

### Re: 15.61

For that question I was also wondering if we would be given the formula on the final formula sheet? I don't think I saw it on the formula sheet posted on the 14B website
Tue Mar 06, 2018 9:54 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Homework 15.23
Replies: 3
Views: 195

### Homework 15.23

Can someone explain to me how to do 15.23 part c? Specifically why you would subtract by .153 when you convert the change in concentration of B to moles per liter of A?
Tue Mar 06, 2018 12:56 am
Forum: General Rate Laws
Topic: 15.19a Order
Replies: 6
Views: 278

### Re: 15.19a Order

I just realized this isn't what the solutions manual did, but it's what made the most sense to me personally
Tue Mar 06, 2018 12:54 am
Forum: General Rate Laws
Topic: 15.19a Order
Replies: 6
Views: 278

### Re: 15.19a Order

Just like in 17, you use the 2 rows where Bs concentration is changing, but As and Cs concentrations are not, which in this case would be experiments 1 and 3. Then you can divide the 2 different B concentrations to get a number to the power of n, and then divide the initial rates to solve for what t...
Tue Mar 06, 2018 12:48 am
Forum: General Rate Laws
Topic: 15.3
Replies: 3
Views: 195

### Re: 15.3

One thing I was confused on was where the 2 came from, so the 2 is because of the stoichiometric coefficient of the reactant? What if there was more than one reactant?
Tue Mar 06, 2018 12:46 am
Forum: Zero Order Reactions
Topic: slope
Replies: 3
Views: 327

### Re: slope

Because all of the graphs he showed were linear, there would be no instance where there is exponential growth or decay?
Tue Mar 06, 2018 12:44 am
Forum: First Order Reactions
Topic: Book Problem 15.21
Replies: 5
Views: 526

### Re: Book Problem 15.21

the solution doesn't plug in 20mg as the initial concentration, but if you do that the same values come out, and i found doing that easier to grasp because you can just directly solve for the final concentration
Tue Mar 06, 2018 12:43 am
Forum: First Order Reactions
Topic: When to use rate equations
Replies: 3
Views: 174

### Re: When to use rate equations

Is or when is a time when you would need to use both?
Tue Mar 06, 2018 12:40 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 Question 6 Part D
Replies: 2
Views: 136

### Re: Test 2 Question 6 Part D

if you used the standard potentials from the equations given on the back of test and didn't flip the signs, and didn't confuse the cathode vs the anode, your work is fine so your answer should be right
Tue Mar 06, 2018 12:37 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Which compound to use
Replies: 3
Views: 159

### Re: Which compound to use

I think they would give you some information or if any assumptions were made, it would probably be for reactions we should know, like combustions where we automatically know O2 is a reactant and H2O is a product
Tue Mar 06, 2018 12:35 am
Forum: Experimental Details
Topic: units
Replies: 4
Views: 484

### Re: units

I personally have a habit of changing mmol/L to just mol/L, but the solutions usually leaves it as mmol/L if that's how it was given in the problem, but I'm assuming unless they explicitly ask for a certain unit or you're solving for the rate which is usually in moles and seconds, it shouldn't matter?
Tue Mar 06, 2018 12:30 am
Forum: General Rate Laws
Topic: 15.17
Replies: 3
Views: 179

### Re: 15.17

Because C is the zeroth order, it's concentration does not change the rate at all, so it's not added to the rate law because the concentration of C doesn't affect the rate. However, I'm not exactly sure if you would be deducted points for including [C]^0 on a test in the rate law equation
Tue Mar 06, 2018 12:27 am
Forum: General Rate Laws
Topic: Test 3 material
Replies: 6
Views: 323

### Re: Test 3 material

So the test doesn't include the slow and fast reactions, right?
Wed Feb 14, 2018 4:12 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: PV = nRT
Replies: 6
Views: 341

### Re: PV = nRT

Also can someone explain why you have delta nRT, but not nRdeltaT? I feel like I've seen the second one being used but usually the change goes towards the number of moles.
Wed Feb 14, 2018 4:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: PV = nRT
Replies: 6
Views: 341

### Re: PV = nRT

if you're using delta v, you're probably going to be using delta nRT, so that something to consider as well
Wed Feb 14, 2018 4:09 pm
Forum: Van't Hoff Equation
Topic: Practice Test
Replies: 5
Views: 618

### Re: Practice Test

I don't think it's gong to be worded the way it was on the practice exam, but you're probably going to need to know the logistics for a conceptual problem.
Tue Feb 06, 2018 12:32 pm
Forum: Student Social/Study Group
Topic: Monday 02/05 Lecture
Replies: 1
Views: 326

### Re: Monday 02/05 Lecture

On Monday we started the section on electrochemistry, which is basically redox reactions and batteries and the like. He introduced galvanic cells and later cell potential an electromotive force. Lucky for you, we won't have those topics on the midterm, which will just be on thermochemistry and therm...
Mon Feb 05, 2018 11:36 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: "Favorability"
Replies: 5
Views: 304

### Re: "Favorability"

Does it also tell us that the reaction is able to happen without an addition of energy?
Mon Feb 05, 2018 11:32 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridges?
Replies: 6
Views: 197

### Re: Salt Bridges?

I think its just negatively charged ions, anions, that are transferred in the salt bridge because the point is to more or less "cancel out" the increase in negative charge going in the direction of the current
Mon Feb 05, 2018 11:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Potential Difference between Electrodes
Replies: 3
Views: 162

### Re: Calculating Potential Difference between Electrodes

I think it has to do with where he mentioned that without a potential difference, the battery ceases to function, so there needs to be some potential difference for the battery to continue to work and as it approaches zero, the battery does not transfer electrons or ions and the battery needs to be ...
Mon Feb 05, 2018 11:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: temperature
Replies: 5
Views: 212

### Re: temperature

I think the sheet Dr. Lavelle gives on the exams says the conversion is 273.15 so I would suggest using that
Mon Feb 05, 2018 11:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Lecture: Gibb's Free Energy
Replies: 1
Views: 59

### Re: Lecture: Gibb's Free Energy

I think it has to do with the idea we learned in Chem 14A that to create more product, you would remove products so that the system creates more in an attempts to have the products and reactants at an equilibrium, so when you remove or have few products, the system replenishes the product needed to ...
Wed Jan 24, 2018 12:28 am
Forum: Phase Changes & Related Calculations
Topic: HW problem 8.19
Replies: 1
Views: 142

### HW problem 8.19

Hey, I'm a little confused on where the addition of 1.48x10^4J came from in number 19. Is it because of the phase change and if so, why that number?
Tue Jan 23, 2018 12:12 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 5
Views: 222

### Re: Standard State

Also does this mean we are expected to know which state any given substance will be in at an average of 25 degrees C?
Tue Jan 23, 2018 12:11 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 5
Views: 222

### Re: Standard State

So if a substance is not in standard state then we do a phase change or change the pressure?
Wed Jan 17, 2018 1:13 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: internal energy
Replies: 5
Views: 222

### Re: internal energy

Sorry this is a little off topic but does this make Internal energy, or the change in internal energy not a state function because both heat and work are not state functions?
Wed Jan 17, 2018 1:10 am
Forum: Phase Changes & Related Calculations
Topic: Heat and Enthalpy
Replies: 3
Views: 182

### Re: Heat and Enthalpy

So enthalpy is a state function just because the components to make it up are state functions? Is there a more qualitative explanation why enthalpy is a state function?
Wed Jan 17, 2018 1:06 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Capacities
Replies: 6
Views: 148

### Re: Heat Capacities

Is there one that is more commonly given in problems or are they used equally?
Wed Jan 17, 2018 12:53 am
Forum: Phase Changes & Related Calculations
Topic: Why steam burns are worse explained
Replies: 5
Views: 251

### Re: Why steam burns are worse explained

ok thanks guys, so what I got from that was the major concept is that because steam requires a phase change when in contact with the skin but liquid water doesn't, the energy needed to complete the phase change results in more burns.
Thu Jan 11, 2018 12:29 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Equation for a non-state property?
Replies: 4
Views: 183

### Re: Equation for a non-state property?

I think Wilson Yeh wants to know of there is a standard equation that can be applied to situations involving heat or other not state properties that we will have to know? or is the value subjective depending on the situation?
Thu Jan 11, 2018 12:24 am
Forum: Phase Changes & Related Calculations
Topic: Why steam burns are worse explained
Replies: 5
Views: 251

### Why steam burns are worse explained

Hey, could someone please clarify why steam burns are worse than others? I know part of the explanation is that it takes around 40kJ to break liquid water bonds into water vapor, so is the reasoning just that the steam is holding in all that excess energy which causes more severe burns or not?
Fri Dec 08, 2017 10:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Final [ENDORSED]
Replies: 6
Views: 569

### Re: Final[ENDORSED]

While thinking of that, try not to neglect the topics from before the midterms, especially since some like combustion with unknown compound X are worth a lot of points per problem.
Mon Dec 04, 2017 10:39 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Strong or weak? [ENDORSED]
Replies: 3
Views: 610

### Re: Strong or weak?[ENDORSED]

Where can we get this table this year since there is no course reader, is it on the chemistry website or in the textbook?
Mon Dec 04, 2017 10:36 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Strong Acids and Weak Bases
Replies: 1
Views: 253

### Re: Strong Acids and Weak Bases

I am too. I noticed a trend with strong acids including H attached to group 17 atoms(Cl, Br, ect), but HF isn't included so I don't know if HF is a strong acid or not?
Wed Nov 29, 2017 10:06 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Relation between K and Q
Replies: 2
Views: 377

### Re: Relation between K and Q

And I think if there is a larger K than Q, then the equation is going in the forward direction (or to the right) because equilibrium favors the creation of more products?
Wed Nov 29, 2017 10:02 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K constant
Replies: 2
Views: 190

### Re: K constant

And if there are no gas or aqueous solutions on one side of the equation, for example on the products side, we would use 1 as the numerator, right?
Mon Nov 27, 2017 7:46 pm
Forum: Sigma & Pi Bonds
Topic: Hybridization
Replies: 3
Views: 391

### Re: Hybridization

Correct me if I'm wrong, but is hybridization why you can have lewis structures where the central atom doesn't follow the octet rule after the third row?
Mon Nov 27, 2017 7:31 pm
Forum: Bronsted Acids & Bases
Topic: How to judge which is bronsted acids & bases
Replies: 2
Views: 266

### Re: How to judge which is bronsted acids & bases

You can't judge all acids and bases through bronsted right? I think I remember Lavelle saying Lewis Acids and Bases explain more situations of acids and bases?
Mon Nov 20, 2017 3:24 am
Forum: Naming
Topic: Diaqaua
Replies: 9
Views: 492

### Re: Diaqaua

When is aqua vs hydrate used?
Mon Nov 20, 2017 3:18 am
Forum: Naming
Topic: Oxidation State vs. Formal Charge
Replies: 3
Views: 291

### Re: Oxidation State vs. Formal Charge

So generally, an atom can have a formal charge of zero but an oxidation number of, for example, 2-?
Thu Nov 16, 2017 10:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm on myucla
Replies: 6
Views: 436

### Midterm on myucla

Hey, this is really minute but should I be worried if my midterm grade isn't up on myucla? I figure it's fine since I got my exam back but is everyone else's score on myucla?
Wed Nov 15, 2017 1:33 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Electric(?) configuration [ENDORSED]
Replies: 1
Views: 105

### Electric(?) configuration[ENDORSED]

Hey, I was just wondering if we've gone over how to actually solve for electric configuration with sigma and pi bonds or if we've just learned the conceptual things?
Sun Nov 05, 2017 1:29 pm
Forum: Formal Charge and Oxidation Numbers
Topic: formal charge vs. octet
Replies: 3
Views: 338

### Re: formal charge vs. octet

I read silicon and chlorine can also have an expanded octet as well
Fri Nov 03, 2017 9:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Only certain central atoms have a full octet?
Replies: 4
Views: 356

### Re: Only certain central atoms have a full octet?

Yea, I think the priority when making a Lewis Structure is to make sure you have the right number of electrons and that the more electronegative atoms (which are the outer atoms since the central atom is usually the less electronegative atom) have an octet, which may mean the central atom doesn't ge...
Fri Nov 03, 2017 9:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Where is BruinCast?
Replies: 2
Views: 277

### Re: Where is BruinCast?

Im Pretty sure he still has videos covering certain topics under the audio visual modules, so you can use those to relearn some concepts as well.
Fri Oct 27, 2017 12:06 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic vs. Covalent Bonds [ENDORSED]
Replies: 8
Views: 512

### Re: Ionic vs. Covalent Bonds[ENDORSED]

When drawing Lewis structures of ionic bonds on an exam, do you think would we lose points for not having a plus or minus in the top right corner like Lavelle had in class even if we have the right dot structure?
Fri Oct 27, 2017 12:02 pm
Forum: Ionic & Covalent Bonds
Topic: Cations and Anions [ENDORSED]
Replies: 12
Views: 1029

### Re: Cations and Anions[ENDORSED]

Overall, memorizing with some type of correlation or rhyme would probably help with remembering which name goes with which, like I find myself remembering how charges associate with metals or nonmetals but I just mix up the names
Tue Oct 24, 2017 4:52 pm
Forum: DeBroglie Equation
Topic: Momentum [ENDORSED]
Replies: 3
Views: 283

### Re: Momentum[ENDORSED]

Yea, it would be good to know the mass of an electron just as common chem knowledge, but I'm pretty sure he gave the mass of a proton, neutron and an electron on the last exam so you should generally be able to find the mass on the actual exam.
Tue Oct 24, 2017 3:02 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Possible Quantum numbers given n=6
Replies: 3
Views: 259

### Possible Quantum numbers given n=6

So say you have a problem asking for all of the possible quantum numbers given n=6. We know the limits of l are from 0 to n-1, but realistically, we only know that l=0 corresponds with the s orbital, l=1 with p orbital ect, so would it still be technically correct to put l=5 even though we don't kno...
Sun Oct 15, 2017 6:12 pm
Forum: Einstein Equation
Topic: Einstein
Replies: 4
Views: 334

### Re: Einstein

On that note, does anyone know what Einstein called photons during his experimental process or did he just call them generic particles? And did he think they were a unique type of particle, or something that was already established?
Sun Oct 15, 2017 6:05 pm
Forum: Properties of Light
Topic: Photons
Replies: 7
Views: 396

### Re: Photons

Hey, One more small thing to also remember is that in general, energy is proportional to frequency and is inversely proportional to wavelength, remembering this makes solving problems where you're asked a problem with 2-3 frequencies or energy levels a lot easier, especially because you kind of know...
Sun Oct 08, 2017 2:17 pm
Forum: SI Units, Unit Conversions
Topic: Molecules [ENDORSED]
Replies: 10
Views: 622

### Re: Molecules[ENDORSED]

Also, does anyone know why carbon-12 in particular was chosen over other elements or other isotopes of Carbon?
Sun Oct 08, 2017 2:16 pm
Forum: SI Units, Unit Conversions
Topic: Molecules [ENDORSED]
Replies: 10
Views: 622

### Re: Molecules[ENDORSED]

I like to think a moles as a way to have different elements and compounds on the same page since an atom of each element on the periodic table weighs something different, so by converting grams of different molecules to moles, you can get a true image of how much you have of one compound or element ...