## Search found 62 matches

Sun Mar 17, 2019 9:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Vant Hoff equation on formula sheet
Replies: 6
Views: 734

### Re: Vant Hoff equation on formula sheet

yeah it wasnt on the equ sheet
Sun Mar 17, 2019 9:29 pm
Forum: Zero Order Reactions
Topic: Zero Order Rxn
Replies: 7
Views: 390

### Re: Zero Order Rxn

yeah. the equations sheets tell you this.
Sun Mar 17, 2019 1:06 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: pseudo rate law
Replies: 7
Views: 606

### Re: pseudo rate law

its more theoretical for a lab situation. we dont have any calculations with this i dont think
Sun Mar 10, 2019 9:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Final
Replies: 18
Views: 1048

### Re: Final

there will be more of the recent section compared to older ones since we have not been tested on the new topics yet. But study everything.
Sun Mar 10, 2019 9:29 pm
Forum: Zero Order Reactions
Topic: Meaning of Zero, First, and Second Order?
Replies: 4
Views: 222

### Re: Meaning of Zero, First, and Second Order?

the order of a reaction depends on how the concentrations of reactants affect the rate of the reaction. if the reactant concentration does not impact the rate, it is zero order (rate = k). if there is a linear relationship, where the rate and concentration have a direct correlation, it is first orde...
Sun Mar 10, 2019 9:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order for Cell Diagram
Replies: 4
Views: 244

### Re: Order for Cell Diagram

the anode half reaction and cathode half reaction are separated by the double line which represents a salt bridge
Sun Mar 03, 2019 4:34 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard G
Replies: 4
Views: 198

### Re: Standard G

see if there are standard conditions being used
Sun Mar 03, 2019 4:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2 Scores
Replies: 6
Views: 280

### Re: Test 2 Scores

id guess during our next discussion
Sun Mar 03, 2019 4:30 pm
Forum: Zero Order Reactions
Topic: Units of k in Zero Order Reactions
Replies: 4
Views: 211

### Re: Units of k in Zero Order Reactions

M is equal to mol/L so both are the same
Sun Feb 24, 2019 6:07 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n value
Replies: 11
Views: 379

### Re: n value

n is the change in moles of the reaction so you can look at the two sides of the reaction and see the difference
Sun Feb 24, 2019 6:04 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Relation to Enthalpy and Entropy
Replies: 4
Views: 1274

### Re: Relation to Enthalpy and Entropy

these are all related through different equations that are given to us. they are all significant in their own way, as G tells us about spontaneity, and H tells us about endothermic/exothermic.
Sun Feb 24, 2019 6:00 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs and temperature, 9.67 6th ed
Replies: 5
Views: 235

### Re: gibbs and temperature, 9.67 6th ed

if T is 0 it is at absolute zero, which is impossible, and so yes, T has to be greater than 0K.
Sun Feb 24, 2019 5:56 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneous?
Replies: 6
Views: 329

### Re: Spontaneous?

its not that gibbs free energy is negative or positive, but the change in Gibbs tells us if the reaction is spontaneous is not. negative delta G is spontaneous.
Fri Feb 15, 2019 2:26 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Finding the change in H from a reaction/molecules
Replies: 2
Views: 109

### Re: Finding the change in H from a reaction/molecules

for hess's law, if you flip an equation, you change the sign. If you double the contents of a reaction, you double the deltaH value
Fri Feb 15, 2019 2:24 am
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: How to calculate W
Replies: 9
Views: 805

### Re: How to calculate W

W = (# of equal energy conformations)^(# of molecules)
Fri Feb 15, 2019 2:22 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Comparing complex molecules
Replies: 2
Views: 174

### Re: Comparing complex molecules

you should look at the states then the size of the molecules. g > l > s and heavier/more atoms > lighter/less atoms
Sat Feb 09, 2019 11:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 3/2R and 5/2R
Replies: 5
Views: 320

### Re: 3/2R and 5/2R

Eruchi Okpara 2E wrote:So how do we know when to use either 3/2R or 5/2R?

as stated above, use Cv = 3/2 R at constant volume and use Cp = 5/2 R at constant pressure
Sat Feb 09, 2019 11:02 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated System
Replies: 5
Views: 494

### Re: Isolated System

MadelineHlobik wrote:In an isolated system, no energy or matter leave the system right? However in a closed system energy can leave the system?

yes, in a closed system, energy can enter and leave freely.
Sat Feb 09, 2019 11:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: methods
Replies: 8
Views: 427

### Re: methods

aaronharouni wrote:How do you know which method to use when dealing with bond enthalpies?

draw the lewis structures
Sun Feb 03, 2019 6:21 pm
Forum: Phase Changes & Related Calculations
Topic: Steam vs Boiling Water
Replies: 10
Views: 3264

### Re: Steam vs Boiling Water

steam has a lot more energy already put into it that made it go from water to steam, which is why it causes worse burns
Sun Feb 03, 2019 6:13 pm
Forum: Calculating Work of Expansion
Topic: R constant
Replies: 3
Views: 121

### Re: R constant

look at what units your other values are in and use the R that will allow the units to cancel out.
Sun Feb 03, 2019 6:09 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 2nd law of thermodynamics
Replies: 5
Views: 215

### Re: 2nd law of thermodynamics

it says that the total entropy of an isolated system is always increasing. Basically, the more that energy is transformed, the more energy is wasted.
Sun Jan 27, 2019 1:25 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Cancelling Out with Hess's Method
Replies: 3
Views: 977

### Re: Cancelling Out with Hess's Method

the 2NO's are on opposite sides of the equation and therefore will cancel out. however, the O2's are on the same side, so you add them together.
Sat Jan 26, 2019 6:28 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes and Temperature
Replies: 3
Views: 151

### Re: Phase Changes and Temperature

that energy is being used to break bonds
Sat Jan 26, 2019 5:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: method 2
Replies: 2
Views: 112

### Re: method 2

you have to put in energy in order to break bonds. when bonds form, they go to a more stable state so energy is released
Sat Jan 19, 2019 11:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: X Value
Replies: 3
Views: 148

### Re: X Value

yeah. if your estimate is <5% of the original value, then the estimate is ok to use. and the range is 10^-3 to 10^3
Sat Jan 19, 2019 11:26 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Direction of an Acid/Base Reaction
Replies: 2
Views: 365

### Re: Direction of an Acid/Base Reaction

for both Q and K, the products are in the numerator and thus if Q>K, there is an excess of products, and the reaction will proceed in the reverse reaction. likewise, the opposite is true of Q<K
Sat Jan 19, 2019 11:20 pm
Forum: Ideal Gases
Topic: kc vs kp
Replies: 19
Views: 1047

### Re: kc vs kp

Kp is p for partial pressures (gases) and Kc is c for concentration
Sat Jan 12, 2019 11:36 pm
Forum: Ideal Gases
Topic: K and Q
Replies: 7
Views: 314

### Re: K and Q

K is the [products]/[reactants] at equilibrium. Q can be used anytime during the reaction. For instance, at the very start of the reaction, there may be a lot more reactants than products, and at this point, [products]/[reactants] would be Q, not K bc the reaction is not at equilibrium yet.
Sat Jan 12, 2019 11:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.3 example from book
Replies: 3
Views: 180

### Re: 5G.3 example from book

you have to get the net ionic equation and then use that to find K. Also, solids and liquids are not included in K.
Sat Jan 12, 2019 11:30 pm
Forum: Ideal Gases
Topic: Q
Replies: 5
Views: 227

### Re: Q

K is the value at equilibrium, while Q is the value or [products]/[reactants] anytime during the reaction.
if K=Q, the reaction is at equilibrium
if K>Q, then [reactants]>[products] and the forward reaction is favored
if K<Q, then [reactants]<[products] and the reverse reaction is favored
Sat Dec 08, 2018 9:24 pm
Forum: Bronsted Acids & Bases
Topic: Strong acid
Replies: 6
Views: 496

### Re: Strong acid

it is easily ionized
Sat Dec 08, 2018 9:23 pm
Forum: Quantum Numbers and The H-Atom
Topic: Why is this statement incorrect?
Replies: 3
Views: 411

### Re: Why is this statement incorrect?

for ml to be -9, the l value must be at least 9 and the n must be at least 10 which does not exist and it purely theoretical
Sat Dec 08, 2018 9:21 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ranking strong bases
Replies: 2
Views: 88

### Re: ranking strong bases

smaller and highly charged are stronger
Sun Dec 02, 2018 11:19 pm
Forum: Lewis Acids & Bases
Topic: lewis acids & bases
Replies: 3
Views: 237

### Re: lewis acids & bases

if you draw out the lewis structure, you can see if there is a lone pair which would allow a molecule to act as a base, or the opposite for an acid where you can see if there is room for another pair
Sun Dec 02, 2018 11:16 pm
Forum: Hybridization
Topic: Sigma bonds
Replies: 9
Views: 411

### Re: Sigma bonds

marg44 wrote:For these sigma and pi bonds, is one bond stronger than the other? Or are they of equal strength?

i think a sigma bond alone is stronger than a pi bond would be alone, but a pi bond is never alone, it's always on top of a sigma bond
Sun Dec 02, 2018 11:13 pm
Forum: Bronsted Acids & Bases
Topic: Questions
Replies: 2
Views: 195

### Re: Questions

probably both
Sun Nov 25, 2018 9:54 pm
Forum: Sigma & Pi Bonds
Topic: Which bond would break first.
Replies: 15
Views: 1212

### Re: Which bond would break first.

the pi bond will break first because it is weaker than the sigma bond (less overlap).
a double bond is stronger than a single bond because it has a sigma AND pi bond rather than just a sigma bond.
Sun Nov 25, 2018 9:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 38
Views: 1328

### Re: Test 3

so is the test only on the things we learned after the last midterm?
Sun Nov 25, 2018 9:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.109
Replies: 2
Views: 76

### Re: HW 4.109

yeah youre right but <109.5 is still around so the answer key is correct. but in the future for the class we should use <109.5 im pretty sure
Sun Nov 18, 2018 10:40 pm
Forum: Dipole Moments
Topic: Dipole moments in hybridization
Replies: 2
Views: 193

### Re: Dipole moments in hybridization

not every molecule has a permanent dipole, but they do have temporary ones like van der waals forces
Sun Nov 18, 2018 10:34 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power and polarizability
Replies: 2
Views: 169

### Re: polarizing power and polarizability

yeah pretty much. down the group, polarizing power decreases. its the opposite for polarizability
Sun Nov 18, 2018 10:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair influence on shape
Replies: 12
Views: 773

### Re: lone pair influence on shape

the lone pair of electrons has a negative charge that will repel the bonding pairs that also have a negative charge, changing the shape.
Mon Nov 12, 2018 2:19 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 3
Views: 172

### Re: VSEPR

^ the lone pair on the central atom creates a repulsive force on the bonding pairs
Mon Nov 12, 2018 2:15 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 3
Views: 180

### Re: VSEPR

if there are no lone pairs, then the molecule should follow the pattern of being either linear, trigonal planar, or tetrahedral, depending on the number of bonds. if lone pairs are present, the molecule will be bent because the bonding paris will feel repulsion
Mon Nov 12, 2018 2:12 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 5
Views: 292

### Re: Molecular Shape

just look and see if there are any lone pairs. If there are, there will be repulsion with the bonding pairs and thus a bent shape will be formed.
Sun Nov 04, 2018 10:56 pm
Forum: Lewis Structures
Replies: 5
Views: 273

you should calculate the formal charge on each atom and see what bond arrangement gives you a formal charge of 0 on most or all of the atoms.
Sun Nov 04, 2018 10:52 pm
Forum: Octet Exceptions
Topic: Expanded Octet [ENDORSED]
Replies: 5
Views: 182

### Re: Expanded Octet[ENDORSED]

The extra electrons go into the d orbital of the atom. Thats why only elements in rows 3 or higher can have expanded octets, since they have a d orbital.
Sun Nov 04, 2018 10:46 pm
Forum: Lewis Structures
Topic: Expanded Octet Atoms/Exceptions
Replies: 2
Views: 110

### Re: Expanded Octet Atoms

And the elements in rows 3+ can have expanded octets because they have a d orbital that the electrons can fill
Sun Oct 28, 2018 8:29 pm
Forum: Properties of Light
Topic: Measuring Wavelength
Replies: 5
Views: 266

### Re: Measuring Wavelength

He said in class that it would be obvious if a wavelength could be measured or not. He said he wouldn't make the answer something that could be ambiguous and go either direction, so dont worry too much.
Sun Oct 28, 2018 8:27 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.21 7th Edition Question
Replies: 2
Views: 120

### Re: 2A.21 7th Edition Question

Ag is one of the exceptions where the 4d orbital will actually take an e- from the 5s. therefore, the ground state of Ag would be [Kr]4d^10 5s^1. Because in this case Ag is an ion in the form Ag^+, we remove an electron from the 5s orbital, leaving [Kr]4d^10.
Sun Oct 28, 2018 8:09 pm
Forum: Ionic & Covalent Bonds
Topic: Question regarding ionic bonds
Replies: 9
Views: 319

### Re: Question regarding ionic bonds

Yes. Ionic bonds are formed when two atoms have electronegativities that are not close to each other, so that an atom pulls an electron off of another atom. This means two nonmetals do not form ionic bonds because their electronegativities are too close together, as they form covalent bonds instead.
Sun Oct 28, 2018 8:00 pm
Forum: Ionic & Covalent Bonds
Topic: Exceptions to Octet
Replies: 2
Views: 104

### Re: Exceptions to Octet

It's easier for Li and Be to become stable by losing 1 or 2 electrons respectively and becoming like the noble gas He, rather than gaining 6 or 7 electrons to become like Neon.
Wed Oct 17, 2018 11:20 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra
Replies: 4
Views: 230

### Re: Atomic Spectra

Just to reiterate, when the energy difference is smaller, wavelength is larger, and frequency is lower.
Wed Oct 17, 2018 11:16 pm
Forum: Einstein Equation
Topic: The symbol v?
Replies: 16
Views: 2952

### Re: The symbol v?

its actually not the same symbol. velocity is the actual letter 'v' but frequency is the Greek letter nu. It's like a curvy v.
Wed Oct 17, 2018 11:13 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: > vs =
Replies: 1
Views: 49

### Re: > vs =

its saying that the (indeterminacy in position) x (indeterminacy in momentum) >= h/4pi. its always going to be >= because its saying those two factors multiplied will be, at a minimum, h/4pi. Its possible for both position and momentum to be very indeterminate (a large number), but it is not possibl...
Fri Oct 12, 2018 1:47 am
Forum: Balancing Chemical Reactions
Topic: question on "combustion" and "cooking"
Replies: 3
Views: 429

### Re: question on "combustion" and "cooking"

And also, for substances like caffeine that are made up of more than just H,C, and O, there would just be an extra product. in the case of caffeine, because N is in its structure, NO2 would be on the products side to account for this.
Fri Oct 12, 2018 1:42 am
Forum: Molarity, Solutions, Dilutions
Topic: E23 part b
Replies: 4
Views: 507

### Re: E23 part b

No, even though it says SO3 molecules, it still wants you to find the number of moles. The question wants you to treat the molecule as a whole, and find the number of moles of the molecule. In part a you find the number of moles of an ion, and likewise in part b you find the number of moles of a mol...
Fri Oct 12, 2018 1:34 am
Forum: Balancing Chemical Reactions
Topic: Seventh Edition- H21 [ENDORSED]
Replies: 3
Views: 364

### Re: Seventh Edition- H21[ENDORSED]

Yeah to chain off of what the others said, you should start by balancing any of the elements that only appear once on each side of the process. In this case, that would be nitrogen. From there, balance either C or H because they appear the next least (Oxygen should be last because it appears the mos...
Mon Oct 08, 2018 3:58 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: How to understand the questions correctly
Replies: 3
Views: 219

### Re: How to understand the questions correctly

On the test, the questions will most likely specify what units they want the answer in. And if they tell you to to find for example "mass" without units, I assume we should use the base SI units?
Mon Oct 08, 2018 3:48 pm
Forum: SI Units, Unit Conversions
Topic: Homework for Week 2
Replies: 16
Views: 589

### Re: Homework for Week 2

Go to Dr. lavelle's website and click on the syllabus. All of the homework should be listed there, separated by topic. Here's the url https://lavelle.chem.ucla.edu/wp-conten ... SYLL_1.pdf
Mon Oct 08, 2018 3:46 pm
Forum: Empirical & Molecular Formulas
Topic: Going from empirical to Molecular formula
Replies: 14
Views: 1091

### Re: Going from empirical to Molecular formula

the molecular formula will be an exact multiple of the empirical. So the molar mass of the molecular formula divided by the molar mass of the empirical should turn out to be a whole number.