## Search found 63 matches

Fri Mar 15, 2019 4:13 am
Forum: First Order Reactions
Topic: Half life
Replies: 4
Views: 167

### Re: Half life

After deriving the equation you are left with ln(2)/k.
Fri Mar 15, 2019 4:00 am
Forum: General Rate Laws
Topic: Elementary steps
Replies: 1
Views: 110

### Elementary steps

How can you tell if an equation is an elementary step? Is For example, can a single equation for an entire reaction be considered an elementary step?
Fri Mar 15, 2019 3:56 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: activation energy
Replies: 3
Views: 120

### Re: activation energy

There are some hw problems that go over this towards the end of the chapter, but basically you can derive the equation by adding the equations together to get rid of A.
Wed Mar 06, 2019 1:52 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Nerst Equation
Replies: 4
Views: 186

### Re: Nerst Equation

In general, for any problem, I find it helpful to write out all the variables I am given and the variables I need to find. Then, I look at the equation sheet and try to find a way to get from A to B. This will work the same for the Nernst equation.
Wed Mar 06, 2019 1:49 am
Forum: First Order Reactions
Topic: What is the order of a reaction?
Replies: 2
Views: 1860

### Re: What is the order of a reaction?

in other words:

first order: Rate=k[A]
(rate doubles)
second order: Rate=k[A]^2
Wed Mar 06, 2019 1:43 am
Forum: Phase Changes & Related Calculations
Topic: ISOBARIC
Replies: 3
Views: 144

### Re: ISOBARIC

Its usually given in atm, but the conversion, if needed, is on the equation sheet for tests.
Fri Mar 01, 2019 10:15 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H+ in cell diagrams
Replies: 5
Views: 254

### Re: H+ in cell diagrams

H+ is included in the cell diagram.
Fri Mar 01, 2019 10:07 am
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 11
Views: 631

### Re: Phase Changes

I think it is useful and it eliminates confusion when doing phase change problems. I would find is pretty difficult to do they problems without having a good handle on the diagram.
Fri Mar 01, 2019 10:05 am
Forum: Balancing Redox Reactions
Topic: Metals
Replies: 2
Views: 99

### Re: Metals

the lattice structure and delocalization of electrons
Fri Feb 22, 2019 10:24 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G spontaneity
Replies: 7
Views: 604

### Re: Delta G spontaneity

As a side note, you can further solve for when it becomes spontaneous by setting the equation equal to zero and solving for T.
Fri Feb 22, 2019 10:22 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 5
Views: 169

### Re: salt bridge

it connects the oxidation and reduction half-cells of a galvanic cell
Fri Feb 22, 2019 10:20 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isochoric
Replies: 3
Views: 374

### Re: Isochoric

constant volume process
Mon Feb 18, 2019 4:27 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Battery
Replies: 5
Views: 182

### Re: Battery

It is a closed system because although energy can leave and enter the system, matter does not, the matter of acid does not change.
Mon Feb 18, 2019 4:23 pm
Forum: Student Social/Study Group
Topic: Midterms
Replies: 5
Views: 186

### Re: Midterms

Last quarter for Lavella, my roommate emailed her TA to get points back.
Mon Feb 18, 2019 4:22 pm
Forum: Student Social/Study Group
Topic: Best Midterm Review
Replies: 7
Views: 331

### Re: Best Midterm Review

I found the reviews helpful, and sometimes past exams proved beneficial. Also, reviewing lecture notes and the textbook. I thought the midterm went beyond the difficulty for most HW problems, so maybe looking for more difficult problems.
Wed Feb 06, 2019 10:23 pm
Forum: Calculating Work of Expansion
Topic: Isothermal processes
Replies: 2
Views: 131

### Re: Isothermal processes

Isothermal expansion is where temperature stays the same and air is expanded, since heat is lost during work, heat is added.
Wed Feb 06, 2019 10:16 pm
Forum: Phase Changes & Related Calculations
Topic: Symbol inquiry
Replies: 4
Views: 175

### Re: Symbol inquiry

Change in internal energy: ΔU
Internal energy: U
Wed Feb 06, 2019 10:12 pm
Forum: Student Social/Study Group
Topic: Unit Conversion for Temp
Replies: 2
Views: 123

### Re: Unit Conversion for Temp

A good way to tell is to look at the other units you use in the equation. For example, the gas constant includes the unit, K, so you would need to use temperature in Kelvin's for the problem.
Tue Jan 29, 2019 12:20 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 7
Views: 240

### Re: Bond Enthalpies

They are the least accurate because they are an average of all the possible molecular structures they can be in. If you actually compare the methods they are actually pretty similar, but the other two covered methods deal with more exact numbers based on the specific structures in the equations.
Tue Jan 29, 2019 12:16 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Memorizing bond enthalpies
Replies: 5
Views: 220

### Re: Memorizing bond enthalpies

I would assume that you do not need to memorize any both enthalpies. In 14A, we were not expected to do any hard memorization. I would focus on problem solving skills and more conceptual things. Those are both things that Dr.Lavelle has generally shifted his focus to on past exams.
Tue Jan 29, 2019 12:13 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermal Equilibrium
Replies: 5
Views: 151

### Re: Thermal Equilibrium

At equilibrium processes do not suddenly stop happening. So, equilibrium is defined as when the rate of transfer between the surrounds and the system are equal. An example could be a steaming cup of water. If you leave in a room at room temperature eventually the water will go to room temperate when...
Thu Jan 24, 2019 8:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Second deprotonation
Replies: 3
Views: 134

### Re: Second deprotonation

I would assume not just because it wasn’t really covered in lecture or discussion sections.
Thu Jan 24, 2019 8:44 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 7
Views: 262

### Re: Pressure

You only look at gases, ignoring solids and liquids.
Thu Jan 24, 2019 8:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1
Replies: 9
Views: 296

### Re: Test 1

They usually provide all the equations you need to know. I find it best to look at it before the test so you are familiar where everything is.
Fri Jan 18, 2019 2:57 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Acid and Base
Replies: 3
Views: 203

### Re: Acid and Base

If you think of the negative log of 1x10^-14, which is 14. The pH of the acid and the base always add up to 14, in a neutral solution both will be 7. (the below table is found at http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch17/ph.php) Pairs of Equilibrium Concentrations of H3O+ and OH- Ion...
Fri Jan 18, 2019 2:50 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Arrow
Replies: 7
Views: 353

### Re: Equilibrium Arrow

Moreover, you use two arrows for weak acids and bases because there will be some sort of equilibrium where not everything is disassociated.
Fri Jan 18, 2019 2:44 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas
Replies: 3
Views: 117

### Re: Inert Gas

When inert gas is added to a system in equilibrium when pressure is kept constant, the volume will increases and moles on either side will shift. Conversely, if an inert gas is added to a system in equilibrium where volume is kept constant, the pressure will increase but the concentrations will not ...
Fri Jan 11, 2019 12:56 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q vs K
Replies: 5
Views: 205

### Re: Q vs K

Simply put, Q is at any moment and K is when in equilibrium. Q can be used to show change.
Fri Jan 11, 2019 12:53 am
Forum: Student Social/Study Group
Topic: New to Lavelle
Replies: 32
Views: 3922

### Re: New to Lavelle

To post a question you will go to the board index and post under the topic that most closely relates to your question. It will probably be removed or changed if it's posted in the wrong category. After that, you click on the new topic button and ask your question.
Fri Jan 11, 2019 12:42 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5G.11 b
Replies: 3
Views: 143

### Re: 5G.11 b

Solids and liquids are regarded with a value 1 because their effective concentrations stay the same throughout the reaction.
Sat Dec 08, 2018 5:03 pm
Forum: Bronsted Acids & Bases
Topic: Oxoacids
Replies: 1
Views: 119

### Oxoacids

Which are stronger oxoacids or binary acids?
For example: ClOH vs. HCl.
Fri Dec 07, 2018 2:00 am
Forum: *Crystal Field Theory
Topic: Crystal Field Theory
Replies: 5
Views: 915

### Re: Crystal Field Theory

I do not think that we are expected to know this for 14 A.
Fri Dec 07, 2018 1:57 am
Forum: Bronsted Acids & Bases
Topic: Strong Acids vs Weak Acids
Replies: 2
Views: 254

### Re: Strong Acids vs Weak Acids

These are some common strong acids: HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulfuric acid (HSO4- is a weak acid) HBr - hydrobromic acid HI - hydroiodic acid HClO4 - perchloric acid HClO3 - chloric acid @https://www.thoughtco.com/list-of-strong-and-weak-acids-603642 You can also differenti...
Fri Dec 07, 2018 1:45 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Complexes
Replies: 2
Views: 72

### Re: Coordination Complexes

As a side note, a tetrahedral complex is normally formed from AX4, while square planar is usually formed from AX4E2.
Sun Dec 02, 2018 1:35 pm
Forum: Administrative Questions and Class Announcements
Topic: More practice
Replies: 7
Views: 399

### Re: More practice

If you attended any of the review sessions for the midterm, we were given practice problems (as well as the "garlic bread" packet). Also, you might have gotten back previous tests.
Sun Dec 02, 2018 1:22 pm
Forum: Administrative Questions and Class Announcements
Topic: More practice
Replies: 7
Views: 399

### Re: More practice

You could also look at the problems on past tests or previous review sessions.
Sun Dec 02, 2018 1:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Monodentates
Replies: 2
Views: 88

### Re: Monodentates

Yes, monodentates only have one donor atom. Going on, bidentates have two donor atoms.
Sun Dec 02, 2018 1:05 pm
Forum: Naming
Topic: Polydentate
Replies: 2
Views: 86

### Re: Polydentate

A polydentate has more than two lewis base sites.
Tue Nov 27, 2018 12:21 am
Forum: Lewis Acids & Bases
Topic: Difference Between Acids and Bases
Replies: 4
Views: 227

### Re: Difference Between Acids and Bases

Some other indicators are pH values (above 7 is alkaline [base] and less than 7 is acid), and that H+ is usually found in relation to acids, while OH- is usually found in relation to bases.
Tue Nov 27, 2018 12:17 am
Forum: Hybridization
Topic: s-character
Replies: 6
Views: 966

### Re: s-character

It is the ratio of the s orbital to other orbitals. It is usually described by a percentage of s character. For example, sp3 hybrid has 25% s character.
Tue Nov 27, 2018 12:13 am
Forum: Dipole Moments
Topic: Dipole Moment Calculation
Replies: 3
Views: 129

### Re: Dipole Moment Calculation

If we didn't do it in class and it was never talked abut in sections, we probably don't have to do it on the test.
Thu Nov 15, 2018 2:26 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 10
Views: 775

### Re: Formal Charge

It depends on whether or not an element can have an expanded octet. Some elements can only have eight electron so formal charge does not matter because you can't add electrons (however, you might be able to go to a double or triple bond), while others can improve their formal charge (closer to zero)...
Thu Nov 15, 2018 2:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 109.5 Degrees
Replies: 4
Views: 351

### Re: 109.5 Degrees

This is because it is a three dimensional shape so its wont just be 360 divided by the number of sides. This is a link to a mathematical proof laying out how to come to 109.5 degrees. http://www.ctralie.com/Teaching/Tetrahedron/
Thu Nov 15, 2018 2:17 pm
Forum: General Science Questions
Topic: Audio Visuals
Replies: 6
Views: 482

### Re: Audio Visuals

I do not believe so. Lavelle said that he only did them on the topics that he finds students struggle with the most. The most fundamental things.
Thu Nov 08, 2018 1:32 am
Forum: Bond Lengths & Energies
Topic: MIDTERM Bond Length Question
Replies: 15
Views: 532

### Re: MIDTERM Bond Length Question

The experimentally determined bond lengths of all the bonds are the same. Bonds lengths are the average of all of the resonance structures. I also got 130.
Thu Nov 08, 2018 1:17 am
Forum: Administrative Questions and Class Announcements
Topic: Test during Thanksgiving Week?
Replies: 2
Views: 158

### Re: Test during Thanksgiving Week?

The syllabus says "Test 3 Starting Tuesday November 27 in discussion section."
Thanksgiving break is the week prior.
Thu Nov 08, 2018 1:06 am
Forum: Dipole Moments
Topic: Polar and Nonpolar
Replies: 7
Views: 313

### Re: Polar and Nonpolar

Polar: there is an uneven distribution of charge

Nonpolar: there is a completely symmetric distribution of charge

Fri Nov 02, 2018 1:10 am
Forum: Lewis Structures
Topic: How does nitrogen form 4 bonds?
Replies: 3
Views: 4757

### Re: How does nitrogen form 4 bonds?

https://i.stack.imgur.com/Z2n1k.png If you look at the above image you can see that when nitrogen has a positive charge (one less electron), it can form four covalent bonds. Either with single, double, or triple bonds. It is similar to phosphorus in this regard because they both have five valence el...
Fri Nov 02, 2018 1:01 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ionization energy
Replies: 1
Views: 183

### Re: Ionization energy

It is harder to remove the second electron and ever harder to remove the third due to an increase in effective nuclear charge when electrons are removed. The effective nuclear charge is a positive force attracting valence electrons. Therefore, when one electron is removed, the same amount of positiv...
Fri Nov 02, 2018 12:52 am
Forum: Octet Exceptions
Topic: octet rule exceptions?
Replies: 5
Views: 280

### Re: octet rule exceptions?

As a general rule, things become more complicated in terms of an expanded octet 3rd row and down, and the first few elements are stable with only two electrons. I found a more cut and dry rule for octet rule exceptions at this link: https://saylordotorg.github.io/text_general-chemistry-principles-pa...
Fri Oct 26, 2018 2:02 am
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 3
Views: 187

### Re: Drawing Lewis Structures

You bond the atoms where there is either an excess or lack of valence electrons, you know this by placing the electrons in the structure or by visualizing it. The following are two helpful links with step-by-step instructions: http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch01/ch1-3depth.html htt...
Fri Oct 26, 2018 1:57 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: atomic spectra Rydberg
Replies: 3
Views: 173

### Re: atomic spectra Rydberg

Final state - Initial state

We talked about how this is not always so, but for the most part, this is the correct way of thinking about it.
Fri Oct 26, 2018 1:53 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration and Unfilled Orbitals
Replies: 2
Views: 92

### Re: Electron Configuration and Unfilled Orbitals

Another explanation for this is that the most balanced state might not be the one that goes in order with the set rules. Lower energy fills before higher energy, and the most balanced state is strived for as well.
Fri Oct 19, 2018 4:35 pm
Forum: Photoelectric Effect
Topic: Test 2
Replies: 16
Views: 531

### Re: Test 2

You'll still have to know unit analysis and other basic concepts from Test1, but the general concepts tested will be everything up until lecture Friday.
Fri Oct 19, 2018 4:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem Community Due Date
Replies: 6
Views: 276

### Re: Chem Community Due Date

I've heard various things like before lecture Friday or Sunday night. My TA told me to just get it done by Thursday night to be safe.
Fri Oct 19, 2018 4:31 pm
Forum: Quantum Numbers and The H-Atom
Topic: Equation sheet
Replies: 4
Views: 207

### Re: Equation sheet

It's probably a lot like the equation sheet on the front on test 1, which you should have.
Fri Oct 19, 2018 4:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Clarification
Replies: 2
Views: 69

### Re: Electron Configuration Clarification

I believe this is because "l" has to be n-1. n=the first quantum number, and l=the second quantum number.
Thu Oct 11, 2018 11:55 pm
Forum: Significant Figures
Topic: sig figs in periodic table
Replies: 6
Views: 362

### Re: sig figs in periodic table

You always look to the least amount of sig figs in any problem. It makes practical sense because the least number of sig figs determines how precise you can be in your calculations.
Thu Oct 11, 2018 11:53 pm
Forum: Balancing Chemical Reactions
Topic: Writing Chemical Equations
Replies: 2
Views: 454

### Re: Writing Chemical Equations

We haven't gone over it in class yet, but there are a series of procedures for writing the names of chemical formulas. If you are curious, this is a website that goes over how to write chemical formulas: http://www.kentchemistry.com/links/nami ... riting.htm
Thu Oct 11, 2018 11:50 pm
Forum: Einstein Equation
Topic: Units for v(frequency)
Replies: 11
Views: 294

### Re: Units for v(frequency)

They can both be used (and are basically the same thing), but make sure that all units cancel when you reach the end of the problem.
Fri Oct 05, 2018 10:20 pm
Forum: Balancing Chemical Reactions
Topic: Balancing reactions tips
Replies: 29
Views: 1178

### Re: Balancing reactions tips

I usually start with what occurs the least and work through trial and error if I have to. It something is taking too long or not working out make sure you wrote it down correctly because a small mistake at first can turn into a huge hassle in the long run.
Fri Oct 05, 2018 10:17 pm
Forum: Molarity, Solutions, Dilutions
Topic: G13
Replies: 1
Views: 91

### Re: G13

To get you started, you will be using the equation M1V1=M2V2, to calculate what you are missing. This link is for a helpful youtube video on dilution: https://www.youtube.com/watch?v=v6dnEp58mVk
Fri Oct 05, 2018 10:07 pm
Forum: General Science Questions
Topic: Rounding up with Sig Figs
Replies: 3
Views: 202

### Rounding up with Sig Figs

When rounding for sig figs with a number that ends in a five, do you round up or round down? Does it depend on whether it is preceded by an even or odd number? For example, does the number 2.65 for two sig figs go to 2.7 or 2.6? thanks