## Search found 68 matches

Fri Mar 15, 2019 8:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Most Stable Form
Replies: 1
Views: 317

### Most Stable Form

How can we tell if something is in its most stable form? I assumed diatomic molecules like O2, H2, and N2 were in their most stable state but in Lyndon's worksheet for week 4, Q1.A we plugged in bond enthalpies. This must've been explained at the time but I forgot. Does it depend on the reaction?
Thu Mar 14, 2019 1:27 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Determining Catalysts from Diagrams (7E.5)
Replies: 3
Views: 206

### Determining Catalysts from Diagrams (7E.5)

In 7E.5 we are given the diagrams for each step. How do we know which molecule is the catalyst for the reaction? Is it the intermediate or reactant in the first step?
Tue Mar 12, 2019 4:57 pm
Forum: First Order Reactions
Topic: Integrated rate law confusion
Replies: 5
Views: 231

### Re: Integrated rate law confusion

What is the benefit in using one over the other for a particular problem?
Tue Mar 12, 2019 4:54 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow vs Fast Step
Replies: 4
Views: 200

### Re: Slow vs Fast Step

The slow step is always the rate determining step. So the rate of this step will be the overall rate.
Tue Mar 12, 2019 3:17 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding n
Replies: 12
Views: 462

### Re: Finding n

So if one half reaction transfers 2 electrons and the other half reaction transfers 3 electrons, would n be 6? This way they would cancel out in the total reaction.
Tue Mar 12, 2019 2:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 #6 wording
Replies: 1
Views: 128

### Test 2 #6 wording

So for part a mine asks to order from neutral to second oxidation state while part b says second to neutral. The given E cells all go from second oxidization states to neutral so would it be right to use the opposite values for part a and the values given for part b?
Tue Mar 12, 2019 2:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Ordering oxidation and reducing power with E cell
Replies: 1
Views: 93

### Ordering oxidation and reducing power with E cell

If you are ordering in increasing reducing power, do you order from most negative E cell to positive or is it the other way around? And for ordering in increasing oxidation power is it the opposite of what you would put for reducing?
Tue Mar 12, 2019 1:45 pm
Forum: General Rate Laws
Topic: slow step
Replies: 11
Views: 645

### Re: slow step

Jim Brown 14B Lec1 wrote:It is either stated explicitly or has the smaller k value
Why does the slow step have a smaller k value conceptually speaking?
Thu Mar 07, 2019 11:23 am
Forum: Zero Order Reactions
Topic: Order Reactions
Replies: 4
Views: 192

### Re: Order Reactions

Yes zero, first, and second order are all we need to know for this class but there are higher orders.
Tue Mar 05, 2019 10:59 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: k values
Replies: 4
Views: 282

### Re: k values

k is a rate constant and commonly seen as a proportionality constant. You can determine units by plugging in your rates to the rate expression and raising them to the respective exponent (rates are in M/s which is the same as mol/(L*s)). So if k= rate/([A]^2[B]) then k will have the units M^-2 s^-1.
Tue Mar 05, 2019 10:48 pm
Forum: First Order Reactions
Topic: Deriving these equations
Replies: 2
Views: 157

### Re: Deriving these equations

I believe you're okay just knowing the concept and applying it but being able to derive it could give you a better understanding.
Sun Feb 24, 2019 12:32 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: test 3
Replies: 10
Views: 445

### Re: test 3

Maya_Peterson1C wrote:Does anyone know if it will also include entropy and previous thermodynamic concepts?

I don't think it will because those were covered on the midterm but it can't hurt to study those too.
Sun Feb 24, 2019 12:18 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing and Reducing Agent
Replies: 3
Views: 156

### Re: Oxidizing and Reducing Agent

You can look at the oxidation number of an atom and if that number is greater in the product then that is the oxidized substance.
Mon Feb 18, 2019 1:11 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: K and Gibbs Free Energy
Replies: 2
Views: 150

### Re: K and Gibbs Free Energy

Yes when delta G is positive it is an endergonic reaction that favors the reactants.
Wed Feb 13, 2019 8:42 pm
Forum: Calculating Work of Expansion
Topic: Integrals
Replies: 4
Views: 194

### Re: Integrals

As long as you understand the concept you're good. I think that's why Dr. Lavelle purposely leaves out homework problems denoted with the calculus symbol.
Wed Feb 13, 2019 8:39 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Isolated system
Replies: 10
Views: 644

### Re: Isolated system

Another thing to remember is that isolated systems don't have change in internal energy (deltaU=0), meaning q=-w.
Wed Feb 13, 2019 8:37 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Higher Molar Entropy
Replies: 3
Views: 200

### Re: Higher Molar Entropy

Molecules that are more complex, have more possible disorder, or are larger have higher molar entropy.
Fri Feb 08, 2019 1:34 pm
Forum: Calculating Work of Expansion
Topic: Isothermal Expansions
Replies: 3
Views: 169

### Re: Isothermal Expansions

It can be both but I've noticed that more often in our practice problems we see isothermal reversible.
Fri Feb 08, 2019 1:22 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 49
Views: 2279

### Re: Midterm[ENDORSED]

A great way to prepare is doing all the homework problems, attending UA/TA sessions and office hours, as well as watching youtube videos to clarify anything else.
Tue Feb 05, 2019 11:02 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 7th edition 4C.7
Replies: 2
Views: 139

### 7th edition 4C.7

It asks to find the enthalpy of vaporization and gives an amount of moles and an amount of heat. Why do we divide heat by moles to get the answer? Is this derived from another equation or did I miss something? Its simplicity confuses me lol
Wed Jan 30, 2019 11:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Reaction Enthalpies
Replies: 1
Views: 80

### Re: Calculating Reaction Enthalpies

You will know what to use based on the question. It will have certain given aspects that are keys to particular methods.
Wed Jan 30, 2019 11:09 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 5
Views: 246

### Re: Heat Capacity

Extensive properties are dependent on matter measured, like volume and mass. Intensive properties don't depend on amount of matter, like color or density.
Wed Jan 30, 2019 11:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Reaction v. Enthalpy of Formation
Replies: 1
Views: 89

### Re: Enthalpy of Reaction v. Enthalpy of Formation

I saw this question was asked on chem community before and here was their answer: "The reaction enthalpy is the heat given off or taken up for the rxn, i.e., the enthalpy difference between the reactants and products. The enthalpy of formation of a compound is the enthalpy change between the el...
Sat Jan 26, 2019 9:39 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy signs
Replies: 13
Views: 550

### Re: Enthalpy signs

Enthalpy will be positive when the reaction is endothermic meaning it absorbs heat. It is negative when the reaction is exothermic meaning giving off heat.
Wed Jan 23, 2019 8:05 pm
Forum: Ideal Gases
Topic: units for partial pressure of gases
Replies: 6
Views: 384

### Re: units for partial pressure of gases

Use the units given in the question. I don't think we're expected to convert. How do you convert atm to bars?
Wed Jan 23, 2019 7:34 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids and Bases
Replies: 5
Views: 273

### Re: Strong Acids and Bases

The 7 strong acids are HCl,HBr,HI,HNO3,HClO3,HClO4, and H2SO4. The 8 strong bases are LiOH,NaOH,KOH,RbOH,CsOH,Ca(OH)2,Sr(OH)2, and Ba(OH)2. I'd recommend memorizing them because they may be useful in the future.
Tue Jan 22, 2019 9:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids and bases
Replies: 6
Views: 299

### Strong acids and bases

Should we memorize the strong acids and bases so that we know if something is 100% dissociated or not? Or do you think questions will be set up in a way that we know we need to do ICE box?
Wed Jan 16, 2019 11:17 pm
Forum: Ideal Gases
Topic: pressure [ENDORSED]
Replies: 13
Views: 377

### Re: pressure[ENDORSED]

Increasing the temperature will increase the pressure and other factors can change pressure if you consider the equation PV=nRT.
Wed Jan 16, 2019 11:15 pm
Forum: Ideal Gases
Topic: 6th edition 11.81
Replies: 2
Views: 151

### Re: 6th edition 11.81

Plug in your initial that you are given as well as the change that you are given into ice box. Substitute what you don't know for x to start.
Tue Jan 15, 2019 9:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.11 Part b
Replies: 2
Views: 85

### Re: 5J.11 Part b

It requires energy to break a X-X bond, making it an endothermic reaction which favors formation of products.
Thu Jan 10, 2019 11:06 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5G.11 b
Replies: 3
Views: 166

### 5G.11 b

I understand that the reactants are 1 because they are solid and liquid but why do only the aqueous molecules in the product stay in the answer? Is there a certain rule? I know that there is a similar rule for keeping gases when in the reactants.
Thu Jan 10, 2019 10:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Clarification from lecture 1 - Jan 7th
Replies: 3
Views: 142

### Re: Clarification from lecture 1 - Jan 7th

When you know the forward reaction and are trying to find the backward reaction you can simply take the inverse of your answer.
Thu Jan 10, 2019 10:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When to use Kp or Kc
Replies: 3
Views: 114

### When to use Kp or Kc

If a question asks to find K, how do we know whether to make our answer Kp or Kc? I thought that if it is all gases then you use Kp but we have examples where we do the opposite.
Sun Dec 09, 2018 2:29 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 3
Views: 400

### Re: Cisplatin

cisplatin is platinum in the middle with two chlorines on one side (cl) and two ammines on the other (NH3). So there should be four bonds.
Fri Dec 07, 2018 10:48 pm
Forum: Polyprotic Acids & Bases
Topic: Defintion
Replies: 24
Views: 762

### Re: Defintion

Ethan Breaux 1J wrote:Is water then polyprotic?

No water is not a polyprotic acid.
Fri Dec 07, 2018 10:42 pm
Forum: Air Pollution & Acid Rain
Topic: Acid Rain
Replies: 3
Views: 399

### Re: Acid Rain

Sulfur dioxide and nitrogen oxides have the biggest impacts on it.
Tue Dec 04, 2018 12:43 am
Forum: Naming
Topic: Coming up with formula from name
Replies: 3
Views: 144

### Re: Coming up with formula from name

Consult the table on page 723 (7th edition) named toolbox 9C.1. It has all the helpful tips.
Wed Nov 28, 2018 1:20 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: 3F.5 part b (7th Ed.) Melting point
Replies: 4
Views: 223

### Re: 3F.5 part b (7th Ed.) Melting point

Butanol has stronger interactions therefore the melting point is higher. H bonding can usually explain a higher melting point.
Tue Nov 27, 2018 11:24 pm
Forum: Sigma & Pi Bonds
Topic: Which bond would break first.
Replies: 15
Views: 1094

### Re: Which bond would break first.

If pi bonds are weaker than sigma bonds then why are double and triple bonds stronger than single bonds? You are correct that pi bonds are weaker than sigma bonds. When considering why double and triple bonds are stronger than single bonds you should consider that all 3 types have one sigma bond. F...
Tue Nov 27, 2018 10:41 pm
Forum: Dipole Moments
Topic: Interaction Potential Energy
Replies: 4
Views: 454

### Re: Interaction Potential Energy

What is the formula?
Tue Nov 27, 2018 9:55 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8501
Views: 1469065

### Re: Post All Chemistry Jokes Here

The name's bond...sigma bond. (hope you all get the reference)
Mon Nov 19, 2018 7:04 pm
Forum: Hybridization
Topic: Unhybridized orbitals
Replies: 10
Views: 638

### Re: Unhybridized orbitals

"...if the atom has more than three valence electrons in its outer shell three of the electron orbitals hybridize and one of the p orbitals remains unhybridized: It is the unhybridized p orbitals that then form pi bonds for double bonding" (chem.fsu.edu). You may want to go over this link ...
Mon Nov 19, 2018 6:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Different-looking N — H bonds in the Lewis structure for Ammonia (NH3)
Replies: 3
Views: 220

### Re: Different-looking N — H bonds in the Lewis structure for Ammonia (NH3)

These are to show that the atoms are in different planes. They are facing this way because the lone pair makes the molecular shape trigonal pyramidal. Think back to the 3D model Dr. Lavelle showed us in lecture.
Mon Nov 19, 2018 6:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular geometry vs Electronicgeometry
Replies: 3
Views: 191

### Re: Molecular geometry vs Electronicgeometry

What is the difference between molecular geometry vs electronicgeometry? Electronic geometry describes the shape of a molecule based on the number and arrangement of electron pairs around a central atom. Molecular geometry is describing the shape of the molecule in terms of bonds. So if a molecule ...
Mon Nov 19, 2018 6:39 pm
Forum: Hybridization
Topic: Identifying types of bonds and hybridization in Lewis Structures
Replies: 3
Views: 172

### Re: Identifying types of bonds and hybridization in Lewis Structures

If we need to include the types of bonds and show hybridization of orbitals I'm sure it will specify on the test/final. It can't hurt to practice writing it all out on homework problems though.
Wed Nov 14, 2018 10:39 pm
Forum: Hybridization
Topic: Bond Angels
Replies: 5
Views: 315

### Re: Bond Angels

Will molecules of the same shape always have the same bond angles? Like will all tetrahedral molecules etc have the same angles regardless of the molecule? Hypothetically, Molecules of the same shape would have the same bond angles since shape/ molecular geometry is what we use to predict the angle...
Wed Nov 14, 2018 10:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: homework 2E #11 part b
Replies: 2
Views: 184

### Re: homework 2E #11 part b

This link shows a professor who explains the shape of Iodine Trichloride very well.
Wed Nov 14, 2018 10:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moments and VESPR
Replies: 3
Views: 145

### Re: Dipole moments and VESPR

Matthew Tran 1K wrote:The other way around is true as you can use VSEPR to predict whether a molecule has a net dipole moment.

How do you apply VSEPR to predict the net dipole moment?
Wed Nov 07, 2018 12:40 am
Forum: Bond Lengths & Energies
Topic: Bond Lengths
Replies: 6
Views: 283

### Re: Bond Lengths

I don't think you need to memorize them but you may want to know that they are generally between 100 and 200 picometers or 1-2 angstroms.
Wed Nov 07, 2018 12:37 am
Forum: Bond Lengths & Energies
Topic: Resonance Structures
Replies: 4
Views: 184

### Re: Resonance Structures

If you are asked which structure has a longer bond length and both have double bonds, then check how many resonance structures each has. If one has four resonance structures and the other only has two, then you know the one with four resonance structures has longer bond lengths.
Wed Nov 07, 2018 12:34 am
Forum: Bond Lengths & Energies
Topic: Triple Bonds Shorter than Double Bonds
Replies: 4
Views: 792

### Re: Triple Bonds Shorter than Double Bonds

In addition to the above answer, triple bonds are stronger than double bonds because they have a higher pull of electrons.
Tue Oct 30, 2018 2:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Test on Thanksgiving
Replies: 1
Views: 114

### Re: Test on Thanksgiving

Oops nevermind. My mistake I see that it is the week after.
Tue Oct 30, 2018 2:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Test on Thanksgiving
Replies: 1
Views: 114

### Test on Thanksgiving

I see that we have a test the week of Thanksgiving. My discussion is Thursday but we don't have class that day, as it is Thanksgiving. Will the test be moved to the week after or week before?
Tue Oct 30, 2018 1:52 pm
Forum: Ionic & Covalent Bonds
Topic: Number of Unpaired Electrons
Replies: 3
Views: 236

### Re: Number of Unpaired Electrons

You would look at the electrons in the highest sub shell. Everything below the highest sub shell will fill first so any unpaired electrons will be at the top. These are your valence electrons. Remember the rule that electrons are parallel to each each other before two can fill up an orbital. You can...
Tue Oct 30, 2018 1:39 pm
Forum: Student Social/Study Group
Topic: Winter quarter scheduling
Replies: 6
Views: 694

### Re: Winter quarter scheduling

Personally I am holding off on taking Chem 14BL, but if you love chem and have a good understanding of it then its not a bad idea to take them together. It also depends on what your schedule looks like concerning other classes. Taking both may be an overload if you have heavy course loads in your ot...
Tue Oct 30, 2018 1:30 pm
Forum: Student Social/Study Group
Topic: Studying for tests/midterm
Replies: 18
Views: 1656

### Re: Studying for tests/midterm

I would say going to step-up sessions has been super helpful to me since I haven't taken chem since sophomore year. The UA's can be a great help. Also try doing all the assessments that go along with Dr.Lavelle's videos on his website. These are great ways to test yourself and if you get a bad score...
Wed Oct 24, 2018 6:55 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spins
Replies: 4
Views: 194

### Re: Spins

When drawing electron configuration models, another thing to remember is that the electrons are parallel first. This means that there will be an upward arrow in each line drawn before you start pairing them with downward facing arrows.
Wed Oct 24, 2018 6:12 pm
Forum: Quantum Numbers and The H-Atom
Topic: Which electrons have most energy?
Replies: 3
Views: 319

### Re: Which electrons have most energy?

Yes the s sub shell is closer to the nucleus than the p sub shell, therefore it has a lower energy than p. The electrons in 2p are more excited than those in 2s.
Wed Oct 24, 2018 12:19 am
Forum: Properties of Light
Topic: conceptual questions on the test 2?
Replies: 3
Views: 216

### Re: conceptual questions on the test 2?

It's a good idea to study them anyways. Even if these questions aren't asked on Test 2, they may be asked on the midterm or final in the future. The understanding of these concepts will also benefit you when solving problems that will be on the test.
Wed Oct 17, 2018 9:48 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital Interaction
Replies: 2
Views: 111

### Orbital Interaction

Why can't atoms with certain orbitals interact with each other? Dr.Lavelle mentioned the x, y, and z planes but can someone explain it again?
Wed Oct 17, 2018 9:45 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Indeterminacy vs. Uncertainty?
Replies: 4
Views: 195

### Re: Indeterminacy vs. Uncertainty?

You can use both terms but indeterminacy is preferred. The word "uncertainty" implies that we have no idea so "indeterminacy" is used because we have a general idea but aren't exactly sure.
Wed Oct 17, 2018 1:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital like a math function
Replies: 1
Views: 65

### Orbital like a math function

In lecture Dr.Lavelle said that an orbital is like a math function. Will someone explain this please?
Wed Oct 10, 2018 10:41 pm
Forum: Properties of Light
Topic: Telling color by wavelength
Replies: 3
Views: 117

### Telling color by wavelength

Is there a way to know exactly what color light is based on its wavelength? I know that visible light falls between 700nm (red) and 400nm (violet). If something was 515nm, is there a way to define what color that is? Has each color been given a set length of nanometers that defines it? How did peopl...
Wed Oct 10, 2018 10:33 pm
Forum: DeBroglie Equation
Topic: Units in DeBrogile Equation
Replies: 1
Views: 81

### Re: Units in DeBrogile Equation

One joule is equivalent to other units. You can use this equation: 1J = (1kg)*(m^2)*(s^-2). Once substituting joules for these units, you can often cancel certain ones out. For example, J * s is the unit for h, but it can also be written as (1kg)*(m^2)*(s^-1) because of the multiplied s.
Wed Oct 10, 2018 10:22 pm
Forum: Properties of Light
Topic: Light
Replies: 9
Views: 624

### Re: Light

How does amplitude affect frequency? And what is the relationship between the wavelength and frequency? Amplitude doesn't necessarily affect frequency. When thinking of amplitude you can think "How large?" and when thinking about frequency think "How fast?" Wavelength and freque...
Thu Oct 04, 2018 9:08 pm
Forum: SI Units, Unit Conversions
Topic: Fundamental Exercises E27
Replies: 3
Views: 205

### Re: Fundamental Exercises E27

To find the number of water molecules in 1.00 kg of water, you would have to convert the 1.00 kg of water to moles of water (using the molecular mass of water and the relevant equation - don't forget to convert kg to g when using the equation!). Then, once you have the moles of water in 1.00 kg of ...
Thu Oct 04, 2018 9:02 pm
Forum: SI Units, Unit Conversions
Topic: Scientific Notation
Replies: 11
Views: 566

### Re: Scientific Notation

If your number is very large or very small then it is safe to state it in scientific notation. Keep in mind your sig figs when answering.
Wed Oct 03, 2018 5:24 pm
Forum: SI Units, Unit Conversions
Topic: Fundamental Exercises E27
Replies: 3
Views: 205

### Fundamental Exercises E27

This exercise says "Calculate the mass, in grams, of one water molecule". Then it says "Determine the number of water molecules in 1.00 kg of water." I know that for the first one I need to go from molecules to moles to grams. To go from moles to grams I can use molar mass. But h...