## 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: 397

### 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: 318

### 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: 886

### 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: 99

### 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: 146

### 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
Sun Mar 10, 2019 4:06 pm
Forum: Second Order Reactions
Topic: Kinetics on the Final
Replies: 2
Views: 123

### 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: 513

### 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)
Sun Mar 03, 2019 8:32 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard cell potential
Replies: 3
Views: 176

### 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: 132

### 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: 104

### 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.
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: 154

### 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: 1228

### 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.
Sun Feb 24, 2019 5:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ecell
Replies: 13
Views: 417

### Re: Ecell

CELL = E°(Cathode) - E°(Anode)
Tue Feb 19, 2019 1:09 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Replies: 35
Views: 1178

### 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: 234

### 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: 465

### 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: 71

### 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: 423

### 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: 581

### 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: 106

### 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: 305

### 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: 547

### 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: 85

### 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: 173

### 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: 225

### 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: 169

### 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: 117

### 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: 289

### 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: 206

### 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: 196

### 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: 185

### 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: 353

### 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
Sat Dec 08, 2018 3:02 pm
Forum: Naming
Topic: edta 4-
Replies: 2
Views: 100

### 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: 380

### 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: 556

### 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: 232

### 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: 232

### 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: 72

### 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: 278

### 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: 213

### 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: 106

### 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: 182

### 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: 181

### 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: 487

### 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: 208

### 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: 913

### 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
Replies: 4
Views: 192

### 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: 396

### 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: 6915

### 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: 6915

### 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: 6915

### 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: 474

### 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: 350

### 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: 286

### 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: 210

### 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: 172

### 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: 292

### 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: 249

### 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: 240

### 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: 78

### 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: 94

### 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: 74

### 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: 258

### 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.

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