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: 1010
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: 824
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: 1047
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: 1953
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: 594
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: 526
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: 506
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: 581
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: 449
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: 871
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: 1539
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: 586
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: 714
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: 233
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: 1383
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: 351
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: 627
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: 767
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: 914
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: 10103
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: 289
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: 523
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: 5102
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: 338
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: 242
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: 334
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: 542
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: 3370
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: 453
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: 2170
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: 457
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
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: 798
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: 669
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: 235
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: 477
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: 840
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: 421
Re: Questions
probably both
- Sun Nov 25, 2018 9:54 pm
- Forum: Sigma & Pi Bonds
- Topic: Which bond would break first.
- Replies: 15
- Views: 2602
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.
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: 2489
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: 138
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: 349
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: 293
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: 4207
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: 334
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: 353
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: 555
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
- Topic: Garlic Bread 12a
- Replies: 5
- Views: 523
Re: Garlic Bread 12a
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: 486
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: 268
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: 541
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: 252
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: 601
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: 217
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: 456
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: 8605
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: 147
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: 638
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: 756
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: 502
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: 418
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: 985
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: 2101
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.