Search found 61 matches

by Alexa_Henrie_1I
Fri Mar 15, 2019 11:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Past Finals
Replies: 4
Views: 199

Re: Past Finals

If you google "Bruin Test Bank at UCLA" and click the Chemistry tab, there is a 14B final from Lavelle's Winter 2014 class.
by Alexa_Henrie_1I
Fri Mar 15, 2019 10:12 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: residual entropy T=0
Replies: 2
Views: 129

Re: residual entropy T=0

When absolute temperature equals zero (T=0), there is no thermal entropy (no movement). This means that residual entropy is based on the complexity and order of the molecule and its positions.
by Alexa_Henrie_1I
Fri Mar 15, 2019 7:28 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.85 6th Edition
Replies: 1
Views: 45

15.85 6th Edition

Question 15.85 asks us to draw a proposed structure for the activated complex of each chemical reaction given. Will we be required to know how to draw these structures for the final?
by Alexa_Henrie_1I
Thu Mar 07, 2019 2:13 pm
Forum: Van't Hoff Equation
Topic: test 2
Replies: 7
Views: 247

Re: test 2

Could someone who got this question correct explain step by step how they did it? I am still confused with this problem.
by Alexa_Henrie_1I
Sat Mar 02, 2019 6:50 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Spontaneous reactions
Replies: 7
Views: 849

Re: Spontaneous reactions

Many homework problems ask to solve for the temperature at which a reaction is spontaneous. This shows that spontaneity depends on more than it just being exothermic or endothermic and understanding this makes solving these problems easier.
by Alexa_Henrie_1I
Sat Mar 02, 2019 6:34 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Topics
Replies: 6
Views: 92

Re: Final Topics

Yes the final is cumulative and I would focus more on 14B material than things taught in 14A.
by Alexa_Henrie_1I
Sat Mar 02, 2019 6:29 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test #2
Replies: 10
Views: 177

Re: Test #2

Yes, we normally get our tests back the following week in discussion.
by Alexa_Henrie_1I
Fri Feb 22, 2019 12:09 pm
Forum: Balancing Redox Reactions
Topic: sections covered on test
Replies: 4
Views: 84

Re: sections covered on test

Even though we won't be directly tested on Enthalpy and Entropy, we still need to know how to calculate them to use in Gibbs Free Energy so I would make sure to still review them.
by Alexa_Henrie_1I
Fri Feb 22, 2019 12:04 pm
Forum: Van't Hoff Equation
Topic: Practice Problems
Replies: 3
Views: 78

Re: Practice Problems

If you have the sixth edition text book there are homework problems in chapter 11 that deal with the Van't Hoff's equation!
by Alexa_Henrie_1I
Fri Feb 22, 2019 12:00 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy at phase changes
Replies: 2
Views: 60

Re: Gibbs free energy at phase changes

When G=0, there is no energy free to do work.
by Alexa_Henrie_1I
Sat Feb 16, 2019 6:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous vs boiling point?
Replies: 4
Views: 74

Re: Spontaneous vs boiling point?

It would be the reaction's natural tendency to go from a liquid to a gas at T=boiling point.
by Alexa_Henrie_1I
Sat Feb 16, 2019 6:01 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 927092

Re: Post All Chemistry Jokes Here

What do you do with a sick chemist?
If you can't helium, and you can't curium, then you might as well barium.
by Alexa_Henrie_1I
Sat Feb 16, 2019 5:47 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Midterm Grades
Replies: 35
Views: 610

Re: Midterm Grades

They are normally handed out after lecture, not in discussion.
by Alexa_Henrie_1I
Sat Feb 09, 2019 11:16 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Midterm topics
Replies: 3
Views: 82

Re: Midterm topics

We will be tested on Friday's lecture material up to Gibbs Free Energy.
by Alexa_Henrie_1I
Sat Feb 09, 2019 11:11 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: Residual Entropy
Replies: 5
Views: 101

Re: Residual Entropy

Residual entropy is positional entropy. We can find it using SkblnW (this ignores thermal energy).
by Alexa_Henrie_1I
Tue Feb 05, 2019 2:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.57 (Sixth Edition)
Replies: 3
Views: 91

Re: Question 8.57 (Sixth Edition)

I am also confused about this problem. My answer doesn't match the solutions manual either.
by Alexa_Henrie_1I
Sun Feb 03, 2019 11:18 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated System Example
Replies: 4
Views: 75

Re: Isolated System Example

The universe is also considered an isolated system because the energy of the universe is constant.
by Alexa_Henrie_1I
Sun Feb 03, 2019 11:15 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: kJ vs J
Replies: 9
Views: 121

Re: kJ vs J

Lavelle said they are interchangeable so you could use either as long as the answer matches the units.
by Alexa_Henrie_1I
Sun Feb 03, 2019 11:14 am
Forum: Calculating Work of Expansion
Topic: integral work equation
Replies: 2
Views: 47

Re: integral work equation

There are some problems in the text book where the integral equation is needed (for example problem 8.11 in the sixth edition) so I would know how to solve for those.
by Alexa_Henrie_1I
Sun Jan 27, 2019 12:49 pm
Forum: Phase Changes & Related Calculations
Topic: Modules
Replies: 17
Views: 205

Re: Modules

Lavelle posted the modules for only the first two sections in Chem 14A, so he may only post chemical equilibria modules for 14B.
by Alexa_Henrie_1I
Sun Jan 27, 2019 12:44 pm
Forum: Phase Changes & Related Calculations
Topic: State Properties
Replies: 3
Views: 69

Re: State Properties

Work is dependent on the path taken because the intermediate steps taken to get to the final conclusion must be considered rather than just calculating final-initial.
by Alexa_Henrie_1I
Sun Jan 27, 2019 12:37 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 7
Views: 98

Re: Phase Changes

Another way to determine whether a reaction is endothermic or exothermic is by the value of delta H: an endothermic has a positive delta H because the reaction is absorbing energy, whereas an exothermic energy has a negative delta H because it is releasing energy.
by Alexa_Henrie_1I
Thu Jan 17, 2019 3:15 pm
Forum: Student Social/Study Group
Topic: ICE Table
Replies: 5
Views: 88

Re: ICE Table

We can take this short cut when the value of K is < 1x10^-3
by Alexa_Henrie_1I
Thu Jan 17, 2019 3:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 12.23 6th Edition
Replies: 2
Views: 57

Re: 12.23 6th Edition

Okay I understand how the Kw is equal to to x^2 now. Thank you.
by Alexa_Henrie_1I
Thu Jan 17, 2019 9:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 12.23 6th Edition
Replies: 2
Views: 57

12.23 6th Edition

Hello, I am having trouble solving 12.23. Could someone please explain how to go about it? The question asks: The value of Kw for water at body temp (37 degrees C) is 2.1x10^-14. A) What is the molarity of H3O ions and the pH of neutral water at 37 degrees C? B) What is the molarity of OH in neutral...
by Alexa_Henrie_1I
Sun Jan 13, 2019 7:28 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient Meaning
Replies: 2
Views: 45

Re: Reaction Quotient Meaning

Q can be calculated at any given time, whether before equilibria is reached or after equilibria is subjected to change. It's just a measure to see whether more reactants or products are being formed until reaching equilibrium.
by Alexa_Henrie_1I
Sun Jan 13, 2019 7:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6th Edition Hw#11.29
Replies: 2
Views: 48

Re: 6th Edition Hw#11.29

Will we need to know the Gibbs Free Energy equation for the first test?
by Alexa_Henrie_1I
Sat Dec 08, 2018 4:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 11
Views: 262

Re: Polydentate

Is dien tridentate or tetradentate?
by Alexa_Henrie_1I
Thu Dec 06, 2018 10:09 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Conjugate?
Replies: 5
Views: 201

Re: Conjugate?

A conjugate base is the result of an acid donating its protons.
A conjugate acid is the result of a base accepting protons.
by Alexa_Henrie_1I
Thu Dec 06, 2018 9:58 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Size and Polarizability
Replies: 4
Views: 216

Re: Size and Polarizability

Anions get larger as the number of electrons increase because the number of shells increase. Ionic radii increases down a group and decreases across a period. So determining size of anions does depend on the number of electrons but you also have to consider the strength of the nuclear charge and its...
by Alexa_Henrie_1I
Sun Dec 02, 2018 10:13 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: calcium
Replies: 2
Views: 49

Re: calcium

Yes, quick means "active" and slake means to hydrate. This makes sense because calcium hydroxide is formed by mixing calcium oxide with water.
by Alexa_Henrie_1I
Thu Nov 29, 2018 4:54 pm
Forum: Naming
Topic: Common Ligand Names
Replies: 4
Views: 86

Re: Common Ligand Names

Okay, hopefully they will be provided on the final.
by Alexa_Henrie_1I
Wed Nov 28, 2018 2:32 pm
Forum: Naming
Topic: Common Ligand Names
Replies: 4
Views: 86

Common Ligand Names

Are we expected to memorize all of the common ligand names from Table 17.4 (6th edition)?
by Alexa_Henrie_1I
Sun Nov 25, 2018 6:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.21 6th edition
Replies: 2
Views: 38

Re: 4.21 6th edition

The best way to know bond angles is to memorize which bond angles are formed by each shape. Remember that lone pairs can effect these bond angles through repulsion and bond angles would therefore be a little smaller than without lone pairs attached to the molecule.
by Alexa_Henrie_1I
Sun Nov 25, 2018 11:58 am
Forum: Dipole Moments
Topic: What are dipole moments used for?
Replies: 3
Views: 83

Re: What are dipole moments used for?

^this is correct. Atoms with higher electronegativity attract electrons more than atoms with low electronegativity, resulting in a net dipole moment. Remember that electronegativity increases across a period and decreases down a group.
by Alexa_Henrie_1I
Wed Nov 14, 2018 3:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Remembering
Replies: 8
Views: 160

Re: Remembering

^This chart is super helpful thank you for sharing it!
by Alexa_Henrie_1I
Wed Nov 14, 2018 3:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 58

Re: Bond Angles

So the best way to know the angles is just through memorization of the structures right?
by Alexa_Henrie_1I
Tue Nov 13, 2018 8:36 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: hydrogen bonding
Replies: 11
Views: 206

Re: hydrogen bonding

^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs.
by Alexa_Henrie_1I
Fri Nov 09, 2018 3:06 pm
Forum: Bond Lengths & Energies
Topic: Tests
Replies: 5
Views: 133

Re: Tests

Yes to confirm the last test begins in your discussion section the week of November 26th.
by Alexa_Henrie_1I
Fri Nov 09, 2018 2:59 pm
Forum: Bond Lengths & Energies
Topic: Grading
Replies: 3
Views: 111

Re: Grading

I am pretty sure than 93 is an A
by Alexa_Henrie_1I
Thu Nov 08, 2018 4:15 pm
Forum: Dipole Moments
Topic: Polarizability
Replies: 5
Views: 88

Re: Polarizability

Polarizability depends on the number of electrons a molecule has and its size. Increasing size and electrons results in stronger attractive interactions.
by Alexa_Henrie_1I
Sun Nov 04, 2018 7:08 pm
Forum: Lewis Structures
Topic: Question 3.55 (Sixth Edition)
Replies: 6
Views: 96

Re: Question 3.55 (Sixth Edition)

A faster way to find a radical is by counting how many electrons a molecule has. An odd number of electrons would signify a radical whereas an even number of electrons would signify paired electrons.
by Alexa_Henrie_1I
Sun Nov 04, 2018 7:00 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Test 2 Alveoli question
Replies: 5
Views: 226

Re: Test 2 Alveoli question

Yes the position in question 1 is just the diameter, 2x10^-4 m.
by Alexa_Henrie_1I
Sun Nov 04, 2018 2:59 pm
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 11
Views: 144

Re: Lewis Structures

If there are only two atoms in a molecule, does it matter where the atom with the non-lowest ionization atom is put? Like does it matter if it is put to the left or right of the central atom?
by Alexa_Henrie_1I
Sun Oct 28, 2018 12:07 pm
Forum: Ionic & Covalent Bonds
Topic: Second ionization of alkali metals
Replies: 3
Views: 59

Re: Second ionization of alkali metals

Second ionization energy is always higher because after the first electron is removed, the atom is more positive and the protons in the nucleus have a stronger pull on the electrons left
by Alexa_Henrie_1I
Sun Oct 28, 2018 11:55 am
Forum: Ionic & Covalent Bonds
Topic: Valence electrons
Replies: 8
Views: 78

Re: Valence electrons

We write the d group in electron configurations before p groups because the d state is lower in energy than the p state
by Alexa_Henrie_1I
Thu Oct 25, 2018 3:39 pm
Forum: Trends in The Periodic Table
Topic: Sizes of ions and neutral atoms
Replies: 4
Views: 134

Re: Sizes of ions and neutral atoms

It also helps to consider why cations are smaller than their neutral atoms. Cations are smaller because they lose an electron, which decreases the size of the electron cloud.
by Alexa_Henrie_1I
Sun Oct 21, 2018 4:16 pm
Forum: Quantum Numbers and The H-Atom
Topic: 6th Edition HW 2.29
Replies: 2
Views: 41

Re: 6th Edition HW 2.29

Okay this makes sense. Thank you so much!
by Alexa_Henrie_1I
Sun Oct 21, 2018 3:39 pm
Forum: Quantum Numbers and The H-Atom
Topic: 6th Edition HW 2.29
Replies: 2
Views: 41

6th Edition HW 2.29

I don't really understand 2.29, the question asks to identify how many electrons can have the following quantum numbers in an atom. I don't know how to figure out the possible number of electrons that can have a specific quantum number. Can someone explain how to do this?
by Alexa_Henrie_1I
Thu Oct 18, 2018 9:08 pm
Forum: Properties of Light
Topic: Test 2 [ENDORSED]
Replies: 15
Views: 262

Re: Test 2 [ENDORSED]

Nothing from test 1 will be on test 2
by Alexa_Henrie_1I
Sun Oct 14, 2018 8:47 pm
Forum: Properties of Electrons
Topic: Rydberg formula
Replies: 5
Views: 151

Re: Rydberg formula

First plug in n=4 into the formula to solve for the energy at that level. Then do the same for n=2. After calculating these answers, find the difference between the two using Energyfinal-Energyinitial. Finally plug this difference into equation: wavelength=h(c)/E.
by Alexa_Henrie_1I
Sun Oct 14, 2018 8:24 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: post assessment #40
Replies: 2
Views: 34

Re: post assessment #40

Solve for the energy at n=6 and energy at n=5. After finding these two numbers, subtract Energyfinal-Energyinitial. Once you find this difference, plug the answer into equation: wavelength=h(c)/E
by Alexa_Henrie_1I
Tue Oct 09, 2018 8:20 pm
Forum: Photoelectric Effect
Topic: Post-Mod Problem #28
Replies: 4
Views: 72

Re: Post-Mod Problem #28

and mass of e- will always be 9.11x10^-31 for that equation right?
by Alexa_Henrie_1I
Wed Oct 03, 2018 3:13 pm
Forum: Limiting Reactant Calculations
Topic: Finding theoretical yield
Replies: 6
Views: 129

Re: Finding theoretical yield

You only need to know the molar ratio between the limiting reactant and products because the limiting reactant is completely used in the chemical reaction.
by Alexa_Henrie_1I
Wed Oct 03, 2018 1:06 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity and Dilution of a Solution Post Module Assessment Question 25
Replies: 5
Views: 112

Re: Molarity and Dilution of a Solution Post Module Assessment Question 25

Thank you both so much! I just wasn't using .02 L as the initial volume in the equation. Seeing it step by step helped a lot!
by Alexa_Henrie_1I
Tue Oct 02, 2018 3:50 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity and Dilution of a Solution Post Module Assessment Question 25
Replies: 5
Views: 112

Molarity and Dilution of a Solution Post Module Assessment Question 25

I am having a hard time solving question 25 on the Molarity and Dilution post assessment. The question is: 5.00 g of KMnO4 is dissolved in a 150.00 mL flask of water. If 20.00 mL of this solution is removed and placed in a new 2nd 250.00 mL flask and filled with water, what is the concentration of t...
by Alexa_Henrie_1I
Thu Oct 05, 2017 7:58 pm
Forum: Balancing Chemical Reactions
Topic: Percent yield [ENDORSED]
Replies: 6
Views: 488

Re: Percent yield [ENDORSED]

percent yield= actual yield (which will be given to you)/theoretical yield
by Alexa_Henrie_1I
Thu Oct 05, 2017 7:54 pm
Forum: Limiting Reactant Calculations
Topic: Determining Limiting Reactant
Replies: 6
Views: 487

Re: Determining Limiting Reactant

Just to clarify, when determining molar mass of a reactant you don't include the coefficient that was found when balancing the equation right?

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