Search found 102 matches
- Sat Mar 14, 2020 11:42 am
- Forum: Balancing Redox Reactions
- Topic: Endgame 3B
- Replies: 3
- Views: 349
Re: Endgame 3B
The reduction reaction should be Br2 + 2e- --> 2Br-. You would multiply this whole thing by 5 to balance the electrons when trying to write the overall reaction.
- Sat Mar 14, 2020 11:36 am
- Forum: Administrative Questions and Class Announcements
- Topic: online
- Replies: 3
- Views: 258
Re: online
I think that's unclear right now, but Dr. Lavelle should be sending out an email with all of that information probably later today.
- Sat Mar 14, 2020 11:35 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: elementary rate law
- Replies: 4
- Views: 339
Re: elementary rate law
I believe that an elementary rate law corresponds to the rate law for one step of an equation for a multi-step reaction. The overall rate law refers to all the steps of a reaction, and that is determined by the slowest step.
- Sat Mar 14, 2020 11:34 am
- Forum: First Order Reactions
- Topic: k versus k prime
- Replies: 6
- Views: 562
Re: k versus k prime
Yes, like the previous responders have said, k prime generally refers to the reverse reaction rate and k refers to the forward reaction rate.
- Sat Mar 14, 2020 11:33 am
- Forum: Zero Order Reactions
- Topic: zero order reactions
- Replies: 5
- Views: 370
Re: zero order reactions
Zero order reaction rates are independent of [R]. This means that the rate law is just k which makes its units mol/(L x s).
- Sun Mar 08, 2020 11:54 pm
- Forum: Balancing Redox Reactions
- Topic: Reversing the anode
- Replies: 10
- Views: 656
Re: Reversing the anode
The standard cell potentials are written so that each compound is gaining electrons (aka cathode reaction) so if we want the equation where electrons are actually being lost, you have to reverse that standard cell potential value.
- Sun Mar 08, 2020 11:45 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: G=-nFe
- Replies: 7
- Views: 784
Re: G=-nFe
Yes, you basically just need to know that however many electrons you have in your overall balanced equation will be plugged into n.
- Sun Mar 08, 2020 11:42 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cell
- Replies: 7
- Views: 473
Re: Concentration Cell
Like everybody else is saying, a concentration cell just happens when both the anode and cathode have the same electrodes in it but with different concentrations. The most important thing to remember for concentration cells though is that E standard cell is equal to 0.
- Sun Mar 08, 2020 4:00 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetically stable?
- Replies: 10
- Views: 689
Re: kinetically stable?
I believe this means that the reaction's delta G is negative so it is technically spontaneous, but the reaction won't normally proceed because it has such a high activation energy.
- Sun Mar 08, 2020 3:51 pm
- Forum: General Rate Laws
- Topic: slow step
- Replies: 9
- Views: 610
Re: slow step
I believe that the slowest step of a multi-step reaction is the rate-determining step.
- Sun Mar 08, 2020 3:42 pm
- Forum: Zero Order Reactions
- Topic: Not used Half life
- Replies: 8
- Views: 914
Re: Not used Half life
Yes there is a half-life for zero order reactions and it is: [A initial] / 2k
- Sun Mar 08, 2020 2:13 pm
- Forum: General Science Questions
- Topic: Review Packet
- Replies: 14
- Views: 1170
Re: Review Packet
I think we will be getting a review packet that will be gone over in Lyndon's session... at least that's how it worked for Chem 14A. Dr. Lavelle would make an announcement tomorrow in class or sometime this week about that.
- Sun Mar 08, 2020 2:10 pm
- Forum: General Rate Laws
- Topic: Product in Rate Law
- Replies: 2
- Views: 256
Re: Product in Rate Law
I think HI in this case is a solid, and we don't include solids or liquids in the rate law expressions. As far as I know, I believe that if a product is gaseous or aqueous, we would include those.
- Sun Mar 08, 2020 2:04 pm
- Forum: General Rate Laws
- Topic: Graphs of rate laws
- Replies: 8
- Views: 994
Re: Graphs of rate laws
For zero order, the rate law makes a linear graph, which means that the rate just goes at constant k (slope). For first order reactions, the graph is also linear if you plot ln[A] versus time. For second order reactions, the graph is linear is you plot 1/[A] versus time.
- Mon Mar 02, 2020 11:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding Pt?
- Replies: 2
- Views: 184
Adding Pt?
I was wondering when we add an inert electrode to a cell reaction. Is it when the states are aqueous? The solution manual just says "An inert electrode such as Pt is necessary when both oxidized and reduced species are in the same solution."
- Tue Feb 25, 2020 1:07 am
- Forum: Balancing Redox Reactions
- Topic: Reducing Agent versus Reduced Species
- Replies: 2
- Views: 259
Re: Reducing Agent versus Reduced Species
Yes, there is a difference. The reducing agent is the one being oxidized and the reduced species is reduced in the reaction.
- Tue Feb 25, 2020 12:51 am
- Forum: Balancing Redox Reactions
- Topic: Flipping Reactions
- Replies: 4
- Views: 272
Re: Flipping Reactions
Flip whichever one will best fit the equation given. I like to think of it as an addition problem.
- Tue Feb 25, 2020 12:49 am
- Forum: Van't Hoff Equation
- Topic: Converting K back to Kc
- Replies: 5
- Views: 468
Re: Converting K back to Kc
I think Kc can signify K for all intents and purposes at least on the test. Kc is generally most used for the equilibrium constant for a rxn that is made up of aqueous solutions though, and Kp for for gases since Kc stands for concentration and Kp stands for pressure.
- Tue Feb 25, 2020 12:46 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free energy units
- Replies: 4
- Views: 330
Re: Gibbs Free energy units
I believe that in class, we have been mostly using Gibbs free energy in kJ/mol but as Esha said, you can technically put it into whatever units you want it to be in.
- Tue Feb 25, 2020 12:44 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: electrolytic cells
- Replies: 3
- Views: 304
Re: electrolytic cells
Also, I believe Dr. Lavelle said today that in an electrolytic cell, electrical energy is converted into chemical energy,
- Mon Feb 24, 2020 10:05 am
- Forum: Balancing Redox Reactions
- Topic: Oxidation Number of O2 and O3
- Replies: 3
- Views: 443
Re: Oxidation Number of O2 and O3
In cases like this, I usually look at whether the other molecule involved the reaction is being oxidized or reduced, and then use process of elimination.
- Mon Feb 24, 2020 10:00 am
- Forum: Administrative Questions and Class Announcements
- Topic: Thermo
- Replies: 3
- Views: 270
Re: Thermo
I think practice problems are the way to go for thermo. Personally, it is helpful to go through different types of problems and have set techniques for solving them.
- Sun Feb 23, 2020 10:34 pm
- Forum: Balancing Redox Reactions
- Topic: Determining direction of flow
- Replies: 15
- Views: 757
Re: Determining direction of flow
Yes, I believe electrons always move from the anode to the cathode.
- Sun Feb 23, 2020 9:43 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Difference
- Replies: 5
- Views: 320
Re: Difference
There's not really a huge difference. You can apply what we've learned about delta H and delta S to help you find delta G now.
- Sun Feb 23, 2020 9:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What to exclude in K
- Replies: 9
- Views: 566
Re: What to exclude in K
Yup, H2O as a gas is still included in K. Basic rule of thumb is just to exclude anything designated (s) or (l).
- Sun Feb 23, 2020 9:40 pm
- Forum: Balancing Redox Reactions
- Topic: Hydroxide and H+
- Replies: 6
- Views: 377
Re: Hydroxide and H+
I believe you only use hydroxide and H+ to balance a solution only if you are told it is acidic or basic. I would agree with everyone else that you should probably use water to balance things out in a neutral solution.
- Sun Feb 23, 2020 9:39 pm
- Forum: Balancing Redox Reactions
- Topic: Polyatomic Ions
- Replies: 4
- Views: 301
Re: Polyatomic Ions
I memorized all the basic ones and I find that it's really helped me in the homework. On tests, I think he usually gives you the charge but I have found that just knowing the charges and the atoms is way easier for his class.
- Sun Feb 09, 2020 7:45 pm
- 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: Boltzmann Entropy Equation Clarificaiton
- Replies: 3
- Views: 61
Re: Boltzmann Entropy Equation Clarificaiton
Yes, if you have more possible states (aka higher W), there is more entropy in the system. Also, as the previous responder said, I would use the equation when we are given the number of particles/microstates in the question.
- Sun Feb 09, 2020 7:40 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Second law equation
- Replies: 3
- Views: 95
Re: Second law equation
I don't think that this equation shows that entropy always increases in a system. I think during the review session today, we were told to use this only for phase changes.
- Sun Feb 09, 2020 7:38 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Delta S Universe
- Replies: 3
- Views: 125
Re: Delta S Universe
In a reversible reaction, delta S of the system is equal to delta S of the surroundings because delta S of the universe is 0. But I'm pretty sure that the general equation you described in your question applies to all reactions.
- Sun Feb 09, 2020 7:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat & Temperature of Phase Changes
- Replies: 5
- Views: 118
Re: Heat & Temperature of Phase Changes
If you look at the graph Dr. Lavelle drew of q versus T early on in thermochemistry, you can see that at the phase changes, the graph plateaus.
- Sun Feb 09, 2020 7:33 pm
- Forum: Ideal Gases
- Topic: Change in pressure
- Replies: 7
- Views: 490
Re: Change in pressure
I like to think of it as a balancing act. If you decrease the volume on one side which increases the pressure, the reaction will favor the side with less molecules because the pressure needs to go somewhere else, if that makes sense.
- Sun Feb 02, 2020 9:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: negative delta U value
- Replies: 2
- Views: 53
Re: negative delta U value
I believe that if the delta U value is negative, it just means that the temperature was decreased which caused the gas molecules to slow down.
- Sun Feb 02, 2020 8:52 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Quadratic Equation
- Replies: 5
- Views: 433
Re: Quadratic Equation
I just wanted to add that you might be able to avoid doing the quadratic equation is the Ka value is less than 10^-3 or percent ionization is less than 5%.
- Sun Feb 02, 2020 8:37 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Shifts
- Replies: 6
- Views: 409
Re: Shifts
For more clarification on your question, are you asking about how Le Chatelier's works?
- Sun Feb 02, 2020 8:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Purpose
- Replies: 2
- Views: 112
Re: Purpose
Yup, I just wanted to add that bomb calorimeters are used to measure heat of combustion at constant volume and that a calorimeter is used at constant pressure.
- Sun Feb 02, 2020 8:07 pm
- Forum: Phase Changes & Related Calculations
- Topic: Reversible and Irreversible
- Replies: 5
- Views: 198
Re: Reversible and Irreversible
In an irreversible reaction, reactants will create a product that cannot be then turned back into reactants.
- Sun Jan 26, 2020 9:02 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy of phase changes
- Replies: 8
- Views: 226
Re: enthalpy of phase changes
I would think that since heat is required to make those phase changes, the reaction would be endothermic. Therefore, delta H would have to be positive.
- Sun Jan 26, 2020 8:47 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 7
- Views: 215
Re: Phase Changes
Yes, as the previous response said, you must add the enthalpy of the phase change.
- Sun Jan 26, 2020 8:08 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Method 2
- Replies: 4
- Views: 145
Re: Method 2
I think the method you are referring to is using bond enthalpies to calculate delta H. In class, Dr. Lavelle said that this was a less accurate way of finding delta H than using Hess' Law. I'm not quite sure if that means we would be tested on it, but it is possible he could give us bond enthalpies ...
- Sun Jan 26, 2020 8:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U
- Replies: 2
- Views: 120
Re: Delta U
From a mathematical standpoint, Delta H is the change in enthalpy and this is equal to change in U +P*delta V.
- Sun Jan 26, 2020 2:42 pm
- Forum: Phase Changes & Related Calculations
- Topic: Combustion
- Replies: 5
- Views: 141
Re: Combustion
Not entirely... combustion does include these processes (for example, carbon and H2O molecules are oxidized in a combustion reaction, but all of these actions are not the same.
- Sun Jan 19, 2020 12:48 am
- Forum: Ideal Gases
- Topic: Ideal gas law and [P]/[R]
- Replies: 3
- Views: 120
Re: Ideal gas law and [P]/[R]
I believe we are supposed to use the ideal gas equation only when we need to convert from Kp to Kc (from bars to moles).
- Sun Jan 19, 2020 12:37 am
- Forum: Ideal Gases
- Topic: Topics on Test 1
- Replies: 37
- Views: 1255
Re: Topics on Test 1
I believe that my TA told me the first test would cover both equilibria as well as what we learned up until Wednesday about Acids/Bases.
- Sun Jan 19, 2020 12:34 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Identifying Acids, Bases, and Salts in a Rxn
- Replies: 4
- Views: 230
Re: Identifying Acids, Bases, and Salts in a Rxn
I would look at proton/electron transfers to identify acids and bases (depending on whether you are talking about Lewis/Bronsted). If something is donating a proton or accepting electrons, it is an acid. If something is accepting a proton or donating an electron, it is a base. Salts, as a previous p...
- Sun Jan 19, 2020 12:28 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Buffers
- Replies: 3
- Views: 211
Re: Buffers
I believe that buffers are mixtures of weak acids and their conjugate bases, so whenever an acid or base is added, it can use either its products or reactants to neutralize the solution.
- Sun Jan 19, 2020 12:24 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Decreasing pressure
- Replies: 4
- Views: 145
Re: Decreasing pressure
I personally like to think of the system trying to alleviate stress within itself. So if pressure is increased on one side, it wants the reaction to go the other way to relieve it.
- Sun Jan 12, 2020 6:06 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: the "quick way"
- Replies: 4
- Views: 259
Re: the "quick way"
I like to think of the "quick way" Dr. Lavelle referred to in class as just a balancing act. If there's more pressure on one side, the reaction will want to go to the other, if that makes sense.
- Sun Jan 12, 2020 6:04 pm
- Forum: Ideal Gases
- Topic: P=(n/v)RT
- Replies: 12
- Views: 949
Re: P=(n/v)RT
n/V is also a way of writing molarity since its units are mols/L. This is nice for understanding how you can use the ideal gas equation to determine Kc as well I believe.
- Sun Jan 12, 2020 6:02 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Situations in which Q=K
- Replies: 7
- Views: 329
Re: Situations in which Q=K
If Q=K, as everybody has been saying, you know the equation has reached its equilibrium. However, K really is the right way to label the ratio of reactants to products at equilibrium.
- Sun Jan 12, 2020 6:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding K: liquids and aqueous
- Replies: 7
- Views: 224
Re: Finding K: liquids and aqueous
Yes, this is the same case for solids. Their concentrations do not change.
- Sun Jan 12, 2020 5:58 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K
- Replies: 6
- Views: 376
Re: Q and K
K never changes since the equilibrium will always have the same ratio of reactants to products. However, Q values can change depending on how far along into a reaction you are since they are not calculated at equilibrium. Depending on if the equation is shifted to the left or the right, there can be...
- Sun Dec 08, 2019 8:33 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: polydentate
- Replies: 4
- Views: 334
Re: polydentate
Yes, the definition of a ligand is just that it is a Lewis base and can donate at least one pair of electrons.
- Sun Dec 08, 2019 8:25 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Strong Acids
- Replies: 2
- Views: 192
Re: Strong Acids
Yes, I was also told by my TA that it would be easiest just to memorize the above list for strong acids.
- Sun Dec 08, 2019 8:24 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty
- Replies: 1
- Views: 245
Re: Uncertainty
I believe that all of the questions asked about Heinsenberg's have included values for delta x and/or delta p (or some portion of delta p like mass).
- Sun Dec 08, 2019 8:16 am
- Forum: Calculating the pH of Salt Solutions
- Topic: kbr?
- Replies: 3
- Views: 357
Re: kbr?
If we look at each ion in KBr, we get K+ and Br-. K+ is a Group 1 metal, which means it has too small of a charge to affect the pH of the solution. If Br- accepts a hydrogen like it wants to (because it's an anion), it will form HBr, which is a strong acid and immediately completely dissociate into ...
- Sun Dec 08, 2019 8:14 am
- Forum: Naming
- Topic: ion at end of name
- Replies: 4
- Views: 423
Re: ion at end of name
Yup, if there are no cations or anions attached to it, you also add "ion" at the end of the name.
- Sun Dec 01, 2019 5:25 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: chelate complex
- Replies: 1
- Views: 133
Re: chelate complex
As far as I know, coordination compounds involving polydentate ligands are considered chelates.
- Sun Dec 01, 2019 4:53 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Kb
- Replies: 2
- Views: 163
Re: Kb
Just like for Ka, Kb is calculated by this equation: [B+][OH-]/[BOH]. A lower Kb value indicates a stronger base.
- Sun Dec 01, 2019 4:50 pm
- Forum: Naming
- Topic: Cis & Trans
- Replies: 3
- Views: 233
Re: Cis & Trans
I believe that the molecular name should stay the same. Cis and trans are used only to specify which isomer you are referring to.
- Sun Dec 01, 2019 3:22 pm
- Forum: Naming
- Topic: Roman Numeral
- Replies: 13
- Views: 857
Re: Roman Numeral
I have personally not seen an instance where the transition metal has a negative anion charge if the charge is designated by a parentheses. If I see a roman numeral, I assume it's "plus whatever that charge is" and it works for me.
- Sun Dec 01, 2019 3:21 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pKa
- Replies: 4
- Views: 219
Re: pKa
As everyone above has said, the pKa constant can tell you the strength of an acid, but this number is generally used for weak acids.
- Sun Nov 24, 2019 2:20 pm
- Forum: Bronsted Acids & Bases
- Topic: Naming Acids and Bases
- Replies: 2
- Views: 189
Re: Naming Acids and Bases
Yes, considering that the final will entail everything we have covered in lectures this quarter, I would assume naming will also be on the final.
- Sun Nov 24, 2019 2:12 pm
- Forum: Biological Examples
- Topic: Cisplatin
- Replies: 15
- Views: 613
Re: Cisplatin
Cisplatin, unlike transplatin, can bond to the same piece of DNA with two bonds to block DNA replication. This lack of replication can kill cancerous cells. The structure of transplatin makes it so that it can only bond at one site on DNA, which is not strong enough to stop DNA replication.
- Sun Nov 24, 2019 2:08 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: dipole-dipole in a solid phase vs gas phase
- Replies: 15
- Views: 1122
Re: dipole-dipole in a solid phase vs gas phase
I'm pretty sure that in one of the UA sessions we were told to think of dipole-dipole in the gas phase as induced dipole-induced dipole, which is a very weak IMF.
- Sun Nov 24, 2019 12:59 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Bronsted vs. Lewis Acids
- Replies: 9
- Views: 490
Re: Bronsted vs. Lewis Acids
Bronsted and Lewis acids essentially mean the same thing but there is a difference in what part of the atom you look at to determine if it's an acid or base. Bronsted acids are proton donors whereas Lewis acids are electron acceptors.
- Sun Nov 24, 2019 12:06 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Identifying Polydentate Ligands
- Replies: 5
- Views: 269
Re: Identifying Polydentate Ligands
As far as I understand, if the ligand binds at more than one site (meaning it donates more than 1 electron pair), it can be considered polydentate.
- Sun Nov 17, 2019 10:46 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Intermolecular Forces and Boiling/Melting Points
- Replies: 3
- Views: 204
Re: Intermolecular Forces and Boiling/Melting Points
Stronger IMF's lead to higher boiling points because they require more energy to break.
- Sun Nov 17, 2019 10:14 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw Shape
- Replies: 3
- Views: 166
Re: Seesaw Shape
When you pick a lone pair position, you want to look for the least amount of electron repulsions. If you pick one of the three equatorial atoms for the positioning of a lone pair, we only have two electron repulsions happening. If you pick one of the two axial atoms for this positioning though, we w...
- Sun Nov 17, 2019 10:11 am
- Forum: Bond Lengths & Energies
- Topic: Dissociation Energy
- Replies: 2
- Views: 220
Re: Dissociation Energy
The dissociation energy is a measure of the strength of a bond. Stronger IMF's such as hydrogen bonding have a higher dissociation energy because it takes more energy to break a strong bond. Weaker IMF's like London forces have a lower dissociation energy.
- Sun Nov 17, 2019 10:07 am
- Forum: Dipole Moments
- Topic: Dipole-Dipole Conti.
- Replies: 2
- Views: 155
Re: Dipole-Dipole Conti.
Yes, it is possible for a molecule to have dipole-dipole bonds and also be nonpolar. If the polarities occur on opposite sides of a molecule between the same atoms, the molecule becomes nonpolar.
- Sun Nov 17, 2019 10:05 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: regions of electron density
- Replies: 10
- Views: 475
Re: regions of electron density
Yes, regions of electron density include both bonds and lone pairs.
- Sun Nov 10, 2019 2:21 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: Is there a difference between Van der Waals and LDF?
- Replies: 5
- Views: 319
Re: Is there a difference between Van der Waals and LDF?
I just wanted to add on that the book uses the term LDF and not Van der Waals, so I personally would stick with that.
- Sun Nov 10, 2019 1:52 pm
- Forum: Bond Lengths & Energies
- Topic: Shape of Molecules and bond strength
- Replies: 5
- Views: 147
Re: Shape of Molecules and bond strength
I believe the example Professor Lavelle used in class was the two rod shaped molecules vs. two spherical shaped molecules. The bonds in the two rod shaped molecules were stronger than the ones in the spherically shaped molecules because they were physically closer together.
- Sun Nov 10, 2019 1:44 pm
- Forum: Dipole Moments
- Topic: Boiling Point
- Replies: 11
- Views: 676
Re: Boiling Point
Boiling point is when a liquid goes to the gas phase, and this requires a release of energy, and this comes from the breaking of these intermolecular bonds. But, stronger bonds mean that they are harder to break. In this way, boiling point could be a useful tool for telling us how strong the IMFs are.
- Sun Nov 10, 2019 1:41 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate Covalent Bond
- Replies: 8
- Views: 588
Re: Coordinate Covalent Bond
There is unequal sharing of electrons in coordinate covalent bonds. In a regular covalent bond, two atoms would be contributing one electron each, but in a coordinate covalent bond, one atom is contributing both electrons.
- Sun Nov 10, 2019 12:22 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: What is hydrogen bonding?
- Replies: 3
- Views: 187
Re: What is hydrogen bonding?
Hydrogen bonds form between oxygen, nitrogen, and fluorine atoms and hydrogen atoms. Oxygen, nitrogen, and fluorine are the only ones that are electronegative enough for this type of bond. But, I would also remember that hydrogen bonds are fairly weak.
- Sun Nov 03, 2019 10:45 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Loss from 4s over 3d?
- Replies: 4
- Views: 1097
Re: Loss from 4s over 3d?
I think you remove electrons with the highest electron affinity first, which in this case would be from the 4s orbital.
- Sun Nov 03, 2019 10:13 am
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate covalent bond?
- Replies: 12
- Views: 1335
Re: Coordinate covalent bond?
The acid would be the electron acceptor and the base is the electron donor.
- Sun Nov 03, 2019 10:07 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: When to calculate formal charge
- Replies: 7
- Views: 337
Re: When to calculate formal charge
Yes, you would want to get the FC as close to zero as possible to get the most stable Lewis structure.
- Sun Nov 03, 2019 9:56 am
- Forum: Resonance Structures
- Topic: Defining Resonance Structures
- Replies: 3
- Views: 141
Re: Defining Resonance Structures
Resonance structures I believe only apply to when there are multiple ways of drawing the exact same structure. For example, moving the location of a double bond would make another resonance structure.
- Sun Nov 03, 2019 9:49 am
- Forum: Dipole Moments
- Topic: Dipole Moments
- Replies: 3
- Views: 84
Re: Dipole Moments
As we discussed in class on Friday, increasing difference in electronegativity means increasing ionic character of a covalent bond, and that charge difference (electric dipole moment) can be measured.
- Fri Oct 25, 2019 11:21 pm
- Forum: Properties of Light
- Topic: visible light
- Replies: 2
- Views: 124
Re: visible light
Personally, I would just know generally what categories the different wavelengths fall into. X-rays/gamma rays are less than 3 nm, UV rays are up to 350 nm, visible light is from 400-700 nm, infrared light is 1000 nm, and microwaves and radio waves are greater than 3x10^6 nm.
- Fri Oct 25, 2019 11:17 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 1D 15
- Replies: 2
- Views: 73
Re: 1D 15
Yup, I just wanted to elaborate on what the person before me said. The angular momentum (l) is based on the orbital you are talking about. So, it's 0 for the s-orbital, 1 for the p-orbital, 2 for the d-orbital, and 3 for the f-orbital.
- Fri Oct 25, 2019 11:15 pm
- Forum: Ionic & Covalent Bonds
- Topic: Meaning of Brackets
- Replies: 7
- Views: 335
Re: Meaning of Brackets
The brackets denote a noble gas, and it's just used for efficiency purposes so you don't have to use a huge list to describe the ground state of an atom.
- Fri Oct 25, 2019 11:12 pm
- Forum: Lewis Structures
- Topic: Double Bonds
- Replies: 6
- Views: 148
Re: Double Bonds
I agree with the person before me who suggested using double bonds first when you are trying to satisfy the octet rule after you have figured out how many total electrons belong in that molecule. After that, you can use double bonds to make the FC equal to 0 for resonance structures.
- Fri Oct 25, 2019 3:26 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond length
- Replies: 11
- Views: 399
Re: Bond length
Yes, Prof Lavelle did mention that the bond lengths of these atoms are not actually shorter or longer in real life. This is contrary to what a lot of textbooks will tell you (at least in my experience), and I think it's important in understanding conceptually what resonance structures really are.
- Thu Oct 17, 2019 2:42 pm
- Forum: DeBroglie Equation
- Topic: Constant Question
- Replies: 7
- Views: 313
Re: Constant Question
On tests, I personally would just use all of the figures in the constants the sheet gives you to get the most accurate number. Even in doing informal practice problems, I would use 6.626 because changing the number to 6.63 will give you a slightly different answer and sometimes you don't know if it'...
- Thu Oct 17, 2019 2:30 pm
- Forum: Properties of Electrons
- Topic: 1B.15
- Replies: 1
- Views: 109
Re: 1B.15
According to the equations Professor Lavelle gave us in the presentation in class, E of the photon = E of energy required to remove the electron + kinetic energy According to the Photoelectric Experiment, it is the incoming photons that release the electrons from the metal surface. You can't really ...
- Thu Oct 17, 2019 2:27 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect and Kinetic Energy
- Replies: 2
- Views: 135
Re: Photoelectric Effect and Kinetic Energy
Yes, you are correct. The electron would be released but it really wouldn't travel since KE = 0.
- Thu Oct 17, 2019 12:56 pm
- Forum: DeBroglie Equation
- Topic: De Broglie's Equation
- Replies: 17
- Views: 552
Re: De Broglie's Equation
The first equation you've listed is the De Broglie equation and that's used for electrons or objects that have a mass. You cannot use light with the De Broglie equation. The second equation you CAN use for photons (light).
- Thu Oct 17, 2019 12:27 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Advice for studying
- Replies: 92
- Views: 6512
Re: Advice for studying
My routine so far has been to go to lecture and then to come back to my room and then watch the video modules again so that I can try to recall the same information that he just went over. I try to spread out my homework problems over the week so that I'm forced to remember how to do certain things ...
- Sat Oct 12, 2019 8:08 pm
- Forum: Properties of Electrons
- Topic: Wavelike vs Particle-like Behavior
- Replies: 6
- Views: 233
Re: Wavelike vs Particle-like Behavior
Dr. Lavelle made a point in class on Friday that kind of cleared things up for me. He said that if you imagine two holes, particles would just go through one but waves would hit both holes at the same time (or at least that's how I interpreted his analogy). Diffraction of light tells us that it has ...
- Sat Oct 12, 2019 7:30 pm
- Forum: Properties of Light
- Topic: 1A #11
- Replies: 3
- Views: 150
Re: 1A #11
Wavelengths are grouped together in certain series so that the principal quantum number for their lower energy level is the same. For example, we know the Lyman series' lower energy level is n=1 and the Balmer series' is n=2.
- Sat Oct 12, 2019 7:14 pm
- Forum: Properties of Electrons
- Topic: Derivation of De Broglie Equation
- Replies: 4
- Views: 125
Re: Derivation of De Broglie Equation
I think you may be referencing when Dr. Lavelle emphasized at the end of his lecture that the De Broglie equation cannot be applied to light because you need a measurement for the momentum of the object, for which you need also need a mass. Light does not have a mass. Hopefully, this made things a l...
- Fri Oct 11, 2019 9:23 am
- Forum: Photoelectric Effect
- Topic: Wavelengths?
- Replies: 8
- Views: 493
Re: Wavelengths?
Could someone also explain if there is any correlation between amplitude and frequency?
- Fri Oct 11, 2019 9:05 am
- Forum: Molarity, Solutions, Dilutions
- Topic: G27
- Replies: 3
- Views: 274
Re: G27
I'm sorry this is such a late response to your clarification question (I just checked back into this post right now), but I thought that I might answer anyway in case you want to come back to this problem for a midterm/final. I think what you are asking is why the 37.5 g of HCl is on the bottom of t...
- Thu Oct 03, 2019 5:43 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: G27
- Replies: 3
- Views: 274
Re: G27
G27) Yes, when you see a dilution problem the equation you want to use is: (M initial)(V initial) = (M final)(V final) The problem gives us the final values: (M final)(V final) = (0.7436 M)(10 L) = 7.436 mol HCl (formula mass = 36.46 g) We want the same amount of mols of HCl on the other side of the...
- Thu Oct 03, 2019 5:33 pm
- Forum: Significant Figures
- Topic: Sig Figs in Mulitstep Problems
- Replies: 10
- Views: 276
Re: Sig Figs in Mulitstep Problems
Yes, that's what I would do. Keep more figures than you know you need for the sig figs at the end of the problem (you can figure this out by looking at the numbers given in the problem) and then round at the very end for your solution.
- Thu Oct 03, 2019 5:31 pm
- Forum: Properties of Light
- Topic: What does μm mean?
- Replies: 4
- Views: 428
Re: What does μm mean?
That symbol designates micrometers, which is a common unit of measurement for wavelengths of infrared light and biological cells.