Search found 63 matches
- Sun Mar 17, 2019 6:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lavelle's other classes
- Replies: 3
- Views: 711
Re: Lavelle's other classes
From his website, here is the list of courses that Dr. Lavelle teaches: Chem-10A (General Chemistry for Life Science Majors) Chem-14A (Atomic and Molecular Structure, Equilibria, Acids and Bases) Chem-14B (Thermodynamics, Electrochemistry, Kinetics, and Organic Chemistry) Chem-19 (Fiat Lux Seminar: ...
- Sun Mar 17, 2019 6:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Picking up the Final
- Replies: 2
- Views: 531
Re: Picking up the Final
According to Dr. Lavelle's website, you can pick it up at "3034 Young Hall, Week 3, Spring quarter"
- Wed Mar 13, 2019 11:47 am
- Forum: Administrative Questions and Class Announcements
- Topic: Class Curve
- Replies: 11
- Views: 1783
Re: Class Curve
I believe Dr. Lavelle curves the final class grade based on how all of the classes did. He did this in 14A, otherwise I would've ended up with a lower grade than I actually did.
- Tue Mar 12, 2019 6:46 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Answer to parts c and d of problem 15.19
- Replies: 1
- Views: 262
Answer to parts c and d of problem 15.19
15.19 The following data were obtained for the reaction A + B + C -> products: Initial concentration (mmol*L -1 ) Experiment [A] 0 [B] 0 [C] 0 Initial rate((mmol A)*L -1 *s -1 1 1.25 1.25 1.25 8.7 2 2.5 1.25 1.25 17.4 3 1.25 3.02 1.25 50.8 4 1.25 3.02 3.75 457 5 3.01 1.00 1.15 ? For problem 15.19 pa...
- Sun Mar 10, 2019 4:17 pm
- Forum: Balancing Redox Reactions
- Topic: increasing oxidation power
- Replies: 2
- Views: 570
Re: increasing oxidation power
You would rank them in order of increasing standard reduction potential. So a more positive reduction potential = higher oxidizing power.
Mg2+ < Ti2+ < Sn2+
Eo (respectively) = -2.36 V < -1.63 V < -0.14 V
Mg2+ < Ti2+ < Sn2+
Eo (respectively) = -2.36 V < -1.63 V < -0.14 V
- Sun Mar 10, 2019 4:06 pm
- Forum: Second Order Reactions
- Topic: Kinetics on the Final
- Replies: 2
- Views: 311
Re: Kinetics on the Final
Alhough Dr. Lavelle hasn't posted the topics that will be covered on the final, I'm assuming that all of the topics on the Kinetics outline will be present on the final.
- Sun Mar 10, 2019 3:50 pm
- Forum: Balancing Redox Reactions
- Topic: Ranking in order of increasing reducing power
- Replies: 6
- Views: 1651
Re: Ranking in order of increasing reducing power
For increasing reducing power, you would list them in order of decreasing reduction potential.
Pt (Eo = 1.20 V) < Cu (Eo = 0.34 V) < Pb (Eo = -0.13 V)
Pt (Eo = 1.20 V) < Cu (Eo = 0.34 V) < Pb (Eo = -0.13 V)
- Sun Mar 03, 2019 8:32 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Standard cell potential
- Replies: 3
- Views: 456
Re: Standard cell potential
Use the balanced half-equations to determine how many moles of e- are transferred (n).
- Sun Mar 03, 2019 8:29 pm
- Forum: First Order Reactions
- Topic: Homework #15.21
- Replies: 1
- Views: 394
Re: Homework #15.21
Use the equation [A] = [Ao]e-kt, which is derived from ln[A]=-kt+ln[Ao]
- Sun Mar 03, 2019 8:23 pm
- Forum: General Rate Laws
- Topic: Reaction Order
- Replies: 2
- Views: 274
Re: Reaction Order
You use the differential rate law where rate = k[R]n. Solving for n would give you the order of the reaction.
In cases where rate = k[R1]n[R2]m, the overall order of the reaction would be n + m.
In cases where rate = k[R1]n[R2]m, the overall order of the reaction would be n + m.
- Sun Feb 24, 2019 5:37 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: gibbs and temperature, 9.67 6th ed
- Replies: 5
- Views: 620
Re: gibbs and temperature, 9.67 6th ed
If T is negative, that means it goes below 0 K, which is impossible as you cannot go below absolute zero. So yes, temperature (at least in Kelvins) will always be positive.
- Sun Feb 24, 2019 5:36 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Relation to Enthalpy and Entropy
- Replies: 4
- Views: 1582
Re: Relation to Enthalpy and Entropy
ΔG°RXN = ΔH°RXN - TΔS°RXN
G is Gibb's free energy, H is enthalpy, S is entropy. Enthalpy and work are related through the equation ΔU = qP + w = ΔH - PΔV.
It's significant in that a negative ΔG means that the reaction is spontaneous, and the sign of ΔG will depend on the values of ΔH and TΔS.
G is Gibb's free energy, H is enthalpy, S is entropy. Enthalpy and work are related through the equation ΔU = qP + w = ΔH - PΔV.
It's significant in that a negative ΔG means that the reaction is spontaneous, and the sign of ΔG will depend on the values of ΔH and TΔS.
- Sun Feb 24, 2019 5:28 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ecell
- Replies: 13
- Views: 1499
Re: Ecell
E°CELL = E°(Cathode) - E°(Anode)
- Tue Feb 19, 2019 1:09 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Midterm Grades
- Replies: 35
- Views: 2781
Re: Midterm Grades
does anyone know when Test 3 is???
Test 2 will be in your discussion section and starts Tuesday of Week 8.
- Tue Feb 19, 2019 1:07 pm
- Forum: General Rate Laws
- Topic: test 3
- Replies: 6
- Views: 636
Re: test 3
According to Dr. Lavelle's website, Test 3 will cover "Gibbs free energy and electrochemistry up to but not including the Nernst equation"
- Tue Feb 19, 2019 1:06 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible vs irreversible
- Replies: 6
- Views: 955
Re: Reversible vs irreversible
A reversible reaction could be something like N2O4 ↔ 2NO2, while an irreversible reaction could be a combustion reaction.
- Sun Feb 10, 2019 8:49 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 6th edition 9.7
- Replies: 1
- Views: 178
Re: 6th edition 9.7
Just use the equation ∆S = n*C*ln(T2/T1) where C is Cp or Cv depending on if it's constant pressure or constant volume. Cp = (5/2)R and Cv = (3/2)R.
- Sun Feb 10, 2019 8:40 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Molecular Interlude
- Replies: 5
- Views: 839
Re: Molecular Interlude
All the constants should be given to us.
- Sun Feb 10, 2019 8:29 pm
- Forum: Phase Changes & Related Calculations
- Topic: 4.18J or 0.38J
- Replies: 8
- Views: 1272
Re: 4.18J or 0.38J
What are you referring to when you say 0.38 J?
- Sun Feb 03, 2019 6:25 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: MIDTERM MATERIAL QUESTION
- Replies: 2
- Views: 311
Re: MIDTERM MATERIAL QUESTION
Since his outline for Thermodynamics lists chapters 9, 11.3, 11.11 - 11.13, I would assume that all of chapter 9 is fair game for the midterm.
- Sun Feb 03, 2019 6:14 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U
- Replies: 7
- Views: 741
Re: Delta U
Positive delta U means an increase in the internal energy of the system, while negative delta U is a decrease in the internal energy.
- Sun Feb 03, 2019 6:00 pm
- Forum: Phase Changes & Related Calculations
- Topic: Type of systems
- Replies: 12
- Views: 1353
Re: Type of systems
No, an isolated system allows neither energy or matter transfer, but a closed system allows only energy transfer.
- Sun Jan 27, 2019 5:03 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Solving for a reaction's enthalpy
- Replies: 2
- Views: 237
Re: Solving for a reaction's enthalpy
Using bond enthalpies is the least preferable method because it is the least accurate.
- Sun Jan 27, 2019 4:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: death in biological systems
- Replies: 5
- Views: 489
Re: death in biological systems
I think it's talking about how CO2 can cause respiratory acidosis, which can cause death from blood pH becoming too low/acidic.
- Sun Jan 27, 2019 4:41 pm
- Forum: Phase Changes & Related Calculations
- Topic: reversible/irreversible
- Replies: 8
- Views: 842
Re: reversible/irreversible
A good example of an irreversible reaction is combustion.
- Sun Jan 20, 2019 9:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Shortcut method (finding concentration change)
- Replies: 5
- Views: 423
Re: Shortcut method (finding concentration change)
Keep in mind that you can only use the approximation method/shortcut if K < 10^-3.
- Sun Jan 20, 2019 9:41 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 5I.13
- Replies: 2
- Views: 296
Re: 5I.13
And which edition?
- Sun Jan 20, 2019 9:39 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gases
- Replies: 7
- Views: 830
Re: Inert Gases
Inert gas is another term for noble gas. Since the noble gases often do not react with many substances, they were referred to as "inert" gases. The noble gases include helium, neon, argon, krypton, xenon, and radon (group 18 of the periodic table).
- Sun Jan 20, 2019 9:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Conceptual questions
- Replies: 6
- Views: 494
Re: Conceptual questions
Since Test 1 covers Equilibrium and Acid & Base Equilibria, I would guess we would need to know the concepts on their respective outlines (1: Chemical Equilibrium & 2: Acids and Bases).
- Sun Jan 13, 2019 4:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solids and liquids [ENDORSED]
- Replies: 4
- Views: 476
Re: solids and liquids [ENDORSED]
Molar concentration of a pure substance (solid or liquid) does not change in a reaction, so solids and liquids are not included in the K expression
- Sun Jan 13, 2019 4:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Result of Only Adding One of the Reactants
- Replies: 4
- Views: 615
Re: Result of Only Adding One of the Reactants
Then, if you were to remove some reactant would the reaction shift left? Towards the reactants to compensate for the loss?
Yep, since Q > K the reaction will shift towards the reactants.
- Sun Jan 13, 2019 4:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solids in calculating equilibrium constant? [ENDORSED]
- Replies: 8
- Views: 870
Re: solids in calculating equilibrium constant? [ENDORSED]
As Dr. Lavelle said,
Molar concentration of a pure substance (solid or liquid) does not change in a reaction
∴ solids and liquids are not included in K expression
Re: edta 4-
If it is ethylenediaminetetraacetato, it is (edta).
- Sat Dec 08, 2018 2:57 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: strength of base
- Replies: 8
- Views: 848
Re: strength of base
I think strength of bond also factors in for bases. If the OH has a weaker bond to the metal, then it is a stronger base since the OH can more easily separate/dissociate.
- Sat Dec 08, 2018 2:52 pm
- Forum: Biological Examples
- Topic: What should we know for the final?
- Replies: 9
- Views: 1034
Re: What should we know for the final?
Knowing about myoglobin/hemoglobin and the heme complex is probably a good idea as it was also on the Churro practice exam.
- Sun Dec 02, 2018 11:14 pm
- Forum: Bronsted Acids & Bases
- Topic: 6th ed: Fundamentals J.1
- Replies: 4
- Views: 546
Re: 6th ed: Fundamentals J.1
But how would you know which ones lose a proton and which ones gain a proton? See which chemical gains/loses an H + . For example: HCl(aq) + NH 3 (aq) → Cl − (aq) + NH 4 + (aq) HCl would be the acid because it donates a proton to NH 3 and becomes Cl - . NH 3 would be the base because it accepts the...
- Sun Dec 02, 2018 4:04 pm
- Forum: Bronsted Acids & Bases
- Topic: 6th ed: Fundamentals J.1
- Replies: 4
- Views: 546
Re: 6th ed: Fundamentals J.1
A Bronsted acid is a proton donor, and a Bronsted base is a proton acceptor. In this case, NH 3 is a base, HBr is an acid, KOH is a base, H 2 SO 3 is an acid, and Ca(OH) 2 is a base. One tip I generally use is I look at the chemical equation and see which substance loses a proton and which one gains...
- Sun Dec 02, 2018 3:57 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Weak Acid or Weak Base
- Replies: 1
- Views: 194
Re: Weak Acid or Weak Base
It's a net ionic equation: in solution, NaC6H5O dissociates to C6H5O- and Na+. Na+ is neither an acid or base, so it doesn't reaction with water. And since it's a net ionic equation, anything that appears on both sides (in this case, Na+) is taken out of the equation.
- Sun Dec 02, 2018 3:51 pm
- Forum: Lewis Acids & Bases
- Topic: acid names
- Replies: 8
- Views: 758
Re: acid names
I'm not sure, but I think we're probably expected to know the strong acids.
- Tue Nov 20, 2018 11:03 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR
- Replies: 5
- Views: 576
Re: VSEPR
Yes, since electrons repel each other.
- Tue Nov 20, 2018 10:44 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Difference in vocabulary terms
- Replies: 1
- Views: 178
Re: Difference in vocabulary terms
Polarizability is the tendency of the anion to be polarized by the cation. Polarizing power is the ability of a cation to attract valence shell electrons from an anion. Polarization is when two oppositely charged ions approach each other and the cation attracts electrons in the outermost shell of th...
- Tue Nov 20, 2018 10:39 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: higher polarizability
- Replies: 4
- Views: 442
Re: higher polarizability
The smaller cation has a more positive charge, so it would pull electrons more strongly.
- Sun Nov 18, 2018 1:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: electron density/concentration
- Replies: 4
- Views: 501
Re: electron density/concentration
I believe they are the same thing.
- Sun Nov 18, 2018 1:45 pm
- Forum: General Science Questions
- Topic: Audio Visuals
- Replies: 6
- Views: 841
Re: Audio Visuals
Does anyone know of any resources similar to the audio visuals for the other topics this quarter? Do people find Khan academy helpful, or crash course videos?
I think those are helpful for explaining general concepts, but maybe not as good for detailed things.
- Sun Nov 18, 2018 1:34 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Angular vs Bent
- Replies: 4
- Views: 495
Re: Angular vs Bent
Yes. The terms are interchangeable.
- Sun Nov 11, 2018 3:54 pm
- Forum: Properties of Light
- Topic: Test 3
- Replies: 24
- Views: 2207
Re: Test 3
Professor Lavelle hasn't posted the topics yet, but I'm guessing chemical bonds and molecular shape and structure.
- Sun Nov 11, 2018 3:52 pm
- Forum: Hybridization
- Topic: Final Grade
- Replies: 4
- Views: 472
Re: Final Grade
From the syllabus: "Each test and exam has a total score but is not assigned a grade. Only at the end of the class when the class average score (out of 500 points) is known are final grades assigned. This class does not use a curve. Group learning (Chemistry Community, Study Groups, Peer Learni...
- Sun Nov 11, 2018 3:49 pm
- Forum: Bond Lengths & Energies
- Topic: Week 6 Discussion Notes 3A,3I,3K
- Replies: 3
- Views: 611
Re: Week 6 Discussion Notes 3A,3I,3K
Thank you, Joyce!
- Sun Nov 04, 2018 9:32 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 19202
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
For question 13A, can someone please explain why the answer is 2.681x10^-26? I got the 2.681, but for some reason I got x10^-23.
Did you remember to convert the mass into kg?
- Sun Nov 04, 2018 9:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 19202
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
I don't understand why in order of increasing ionization energy, it goes C O N F. I thought it would be C N O F. Anyone know why?
Nitrogen is an exception (so is phosphorus) to the trend in that it has a half-filled subshell, 2p^3, which makes it harder for an electron to be removed.
- Sun Nov 04, 2018 7:48 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 19202
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
What determines the energy of a Lewis structure? Formal charges of all the atoms added together?
- Sun Nov 04, 2018 2:15 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Degeneracy
- Replies: 6
- Views: 711
Re: Degeneracy
To calculate the number of degenerate orbitals, you can use 2l + 1.
- Sun Nov 04, 2018 1:25 pm
- Forum: Properties of Light
- Topic: Standard Units
- Replies: 8
- Views: 809
Re: Standard Units
Wavelength, or lambda, is measured in meters, not meters per second.
- Sun Nov 04, 2018 1:17 pm
- Forum: Empirical & Molecular Formulas
- Topic: garlic bread midterm practice #2
- Replies: 5
- Views: 620
Re: garlic bread midterm practice #2
You probably had a rounding error. The method I used was multiplying the molar mass by each percentage to figure out how many grams of C/H/O were present in glycogen, then I divided those masses by their respective element's molar mass to find the molecular formula.
- Sun Oct 28, 2018 6:10 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: What are degenerate orbitals?
- Replies: 2
- Views: 348
What are degenerate orbitals?
What are degenerate orbitals, and could I have a few examples? This was on test #2, and I was confused as I don't remember it being mentioned in lecture (to the best of my knowledge).
- Sun Oct 28, 2018 6:04 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Peer learning Sessions
- Replies: 3
- Views: 428
Re: Peer learning Sessions
The one that Dr. Lavelle talked about can be found on his website: https://lavelle.chem.ucla.edu/wp-conten ... PL_ALL.pdf
- Sun Oct 28, 2018 5:55 pm
- Forum: Lewis Structures
- Topic: Lewis Structures
- Replies: 8
- Views: 692
Re: Lewis Structures
The number of dots is the number of valence electrons the element has. Since most elements obey the octet rule, they would want 8 electrons (whether they're in the form of bonds or lone pairs)
- Sun Oct 21, 2018 8:19 pm
- Forum: Properties of Electrons
- Topic: Concept Behind Orbitals
- Replies: 6
- Views: 595
Re: Concept Behind Orbitals
Since it takes work to pull an electron away from an atom (as electrons are negative and protons are positive), higher orbitals will have higher energy.
- Sun Oct 21, 2018 8:12 pm
- Forum: DeBroglie Equation
- Topic: Remembering mass of electrons for tests
- Replies: 6
- Views: 581
Re: Remembering mass of electrons for tests
The values of constants are given for quizzes/tests
- Sun Oct 21, 2018 8:05 pm
- Forum: DeBroglie Equation
- Topic: 1B. 25 7th Edition
- Replies: 2
- Views: 240
Re: 1B. 25 7th Edition
You use Heisenberg's Indeterminacy Equation: \Delta p \Delta x\geq \frac{h}{4\pi} The question gives the uncertainty in position (delta x) by stating the diameter of the lead atom, 350 pm. To keep it in SI units, it becomes 3.50 x 10^-10 m. To find the only unknown, delta p (uncertainty in momentum)...
- Sun Oct 07, 2018 4:14 pm
- Forum: Limiting Reactant Calculations
- Topic: Module 3 Question
- Replies: 3
- Views: 223
Re: Module 3 Question
No. According to the law of conservation of mass, in a chemical reaction, the total mass of products must be the same as the total mass of the reactants.
- Sun Oct 07, 2018 4:08 pm
- Forum: Limiting Reactant Calculations
- Topic: Textbook question M3 [ENDORSED]
- Replies: 1
- Views: 444
Re: Textbook question M3 [ENDORSED]
Since the question gives the actual yield of 17.5g of CO2, the theoretical (maximum) yield would have to be found in order to calculate the percentage yield. Using stoichiometry, the given mass of CaCO3 is converterd into moles, which is then used to find how many moles of CO2 are produced from the ...
- Sun Oct 07, 2018 3:56 pm
- Forum: Significant Figures
- Topic: Sig Figs & Molar Mass
- Replies: 4
- Views: 595
Re: Sig Figs & Molar Mass
I normally go by the amount of sig figs of the given numbers. For me, the sig figs given by the problem will generally be fewer than the ones in the molar mass since I go up to thousandths place for it.