Search found 104 matches
- Sun Mar 15, 2020 1:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Athena
- Replies: 34
- Views: 3261
Re: Athena
Thank you so much for everything Dr.Lavelle! I had a great time and I’ll miss being in ur class ;-;. I really loved your passion for teaching and I hope you enjoy your break!
- Sat Mar 14, 2020 5:44 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Ka and Kb
- Replies: 4
- Views: 520
Re: Ka and Kb
Yes, that is correct. Ka for acid HA is equal to [H+][A-]/[HA] and Kb is equal to [OH-][B+]/[BOH]. The a stands for acid, and the b stands for base.
- Sat Mar 14, 2020 5:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Grading Scale
- Replies: 16
- Views: 1147
Re: Grading Scale
He is using the same grading system, and I think it is safe to assume that he will be using the same scale also, since the midterm scores, the only average he revealed, were actually higher than those for 14A, and 14A didn't have a curve at all (might have been a point or so tho).
- Sat Mar 14, 2020 5:40 pm
- Forum: General Science Questions
- Topic: Final Overview
- Replies: 5
- Views: 521
Re: Final Overview
Thermodynamics is what I found to be the most tricky and math-intensive, so I think it would be a good idea to study that.
- Sat Mar 14, 2020 5:40 pm
- Forum: Zero Order Reactions
- Topic: Example Help
- Replies: 6
- Views: 603
Re: Example Help
In a zero order reaction, the rate of reaction does not depend on the concentration of the reactants, so the rate of reaction is constant as the concentration decreases. If you want examples and graphs: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Suppleme...
- Sat Mar 14, 2020 5:37 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: heterogeneous catalyst
- Replies: 4
- Views: 343
Re: heterogeneous catalyst
Because it wants to maximize the surface area of the catalyst, so it is able to be involved in more places.
- Sat Mar 14, 2020 5:36 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reaction enthalpy
- Replies: 3
- Views: 327
Re: Reaction enthalpy
If it didn't give you anything else, you can use the individual formation enthalpy of each molecule (from the back of the book) and use addition and subtraction of the products and reactants to find the net enthalpy.
- Sat Mar 14, 2020 5:33 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: What was your favorite chem topic?
- Replies: 137
- Views: 14346
Re: What was your favorite chem topic?
Honestly, I was pretty fond of Molecular shape and structure back in 14A. Not my best unit, but I had a lot of fun.
- Sat Mar 07, 2020 7:26 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding n in G=-nFE
- Replies: 15
- Views: 1067
Re: finding n in G=-nFE
n is the number of electrons exchanged in the general reaction. So you look at the oxidation numbers, and then you look at how they have changed.
- Sat Mar 07, 2020 7:24 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Concentration cell
- Replies: 8
- Views: 635
Re: Concentration cell
Concentration cells are basically just galvanic cells, except the anode and cathode are from the same thing, the only difference between the sides is the concentration.
- Sat Mar 07, 2020 7:23 pm
- Forum: Balancing Redox Reactions
- Topic: confusing homework question
- Replies: 4
- Views: 417
Re: confusing homework question
It is because you need a solid METAL. I2 is not a metal, so you need to add a metal, because you need something to conduct the electrons (metals are able to do this because of metallic bonding, if you remember from Chem 14a, the "sea of electrons" )
- Sat Mar 07, 2020 7:22 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reducing Mass of Electrode
- Replies: 6
- Views: 620
Re: Reducing Mass of Electrode
The electrodes is referring to the solid parts, and changing their masses does not affect the cell potential because solids are not included when calculating Q.
- Sat Mar 07, 2020 7:20 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Electrode masses
- Replies: 8
- Views: 590
Re: Electrode masses
There is no effect because the electrodes are solid.
- Sun Mar 01, 2020 3:12 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding N
- Replies: 6
- Views: 502
Re: Finding N
n refers to the moles of electrons, so you just look at the overall reaction and see how many moles of electrons are transferred, be careful to make sure that you are using the right reaction with the right coefficients for everything!
- Sun Mar 01, 2020 3:09 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: ∆G and ∆G°
- Replies: 7
- Views: 564
Re: ∆G and ∆G°
Yes it does. Take note that ∆G° means that the reaction is spontaneous under STANDARD conditions, hence the "°". However, if it is proceeding under non standard conditions, you would need to use a formula for ∆G in order to find out if it is spontaneous or not.
- Sun Mar 01, 2020 3:07 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Units for delta G
- Replies: 31
- Views: 2174
Re: Units for delta G
Gibbs free ENERGY. delta G is literally referring to a change in energy, so it has the same units as those for energy, which is joules, so the answer would be kJ (kilojoules). Additionally, if you use the equation, you will find that it is kJ
- Sun Mar 01, 2020 3:05 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt bridges
- Replies: 11
- Views: 785
Re: Salt bridges
Salt bridges balance the charges of both sides, by allowing for the transfer of electrons from one side to the other. If there was no salt bridge, then the build-up of ions (cations at the cathode and anions at the anode) would cease the flow of electrons, but the salt bridge allows for ions to be a...
- Sun Mar 01, 2020 3:03 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Standard Cell Potential
- Replies: 3
- Views: 286
Re: Standard Cell Potential
No, they do not always have to be positive. It is just that if it is negative, the reaction will not occur spontaneously, so usually, we are dealing with positive standard cell potentials.
- Sun Feb 23, 2020 10:01 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Spontaneity
- Replies: 8
- Views: 562
Re: Spontaneity
Yes. From the equation ΔG∘=−nFEcell, you can see that if E.cell is positive, then the gibbs free energy would have to be negative, and if the change in gibbs free energy is negative, the reaction is spontaneous.
- Sun Feb 23, 2020 9:52 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Limiting reactant and heat
- Replies: 4
- Views: 616
Re: Limiting reactant and heat
If you know the limiting reactant, then you know exactly how much concentration/amount of reactants are involved in the reaction, and you can calculate extrinsic qualities that depend on quantities, for example the amount of heat acquired/released.
- Sun Feb 23, 2020 9:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ph
- Replies: 8
- Views: 396
Re: Ph
pH is always calculated at equilibrium. If it was not taken at equilibrium they would probably explicitly state at what conditions they found that pH at.
- Sun Feb 23, 2020 9:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What to exclude in K
- Replies: 9
- Views: 672
Re: What to exclude in K
You exclude solids and liquids. Even if it is H2O, you include it if it is explicitly stated as aq or gas
- Sun Feb 23, 2020 9:47 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2
- Replies: 13
- Views: 743
Re: Test 2
Professor Lavelle said the second page of thermo and all of electro (basically everything after the midterm).
- Sun Feb 16, 2020 2:06 am
- Forum: Calculating the pH of Salt Solutions
- Topic: How do you know if something is a salt solution?
- Replies: 6
- Views: 750
Re: How do you know if something is a salt solution?
Salt solutions dissociate in solutions. A "salt" is basically any ionic molecule with anion and cations.
- Sun Feb 16, 2020 2:04 am
- Forum: Student Social/Study Group
- Topic: Curve?
- Replies: 50
- Views: 7059
Re: Curve?
There is no direct curve on the test, but Lavelle adjusts the grading scheme as needed depending on the performance of students overall on test
- Sun Feb 16, 2020 2:02 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: memorize
- Replies: 14
- Views: 887
Re: memorize
Entropy values are given to us.
- Sun Feb 16, 2020 2:01 am
- Forum: Balancing Redox Reactions
- Topic: simplifying half reactions
- Replies: 3
- Views: 254
Re: simplifying half reactions
If you have an equal amount of some molecule on both sides, you can cancel them out, because they don't change through the reaction.
- Sun Feb 16, 2020 2:00 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal Reactions
- Replies: 4
- Views: 350
Re: Isothermal Reactions
Because internal energy is the sum of the energy of a system, and temperature represents the amount of energy in a system (NOT heat!), so if there is no change in energy (which includes heat and work), then there is no change in temperature (and vice versa).
- Sun Feb 09, 2020 9:14 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed system
- Replies: 7
- Views: 396
Re: closed system
Because it is sealed, no matter can get out from within, so no mass exchange can occur. However, because it is not insulated, we know that energy exchange can, so it is not an isolated system. Therefore, it is a closed system, that can exchange energy, but not matter.
- Sun Feb 09, 2020 9:12 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Difference between Cv and Cp?
- Replies: 8
- Views: 541
Re: Difference between Cv and Cp?
Cv is for constant volume, Cp is for constant pressure. For MONOATOMIC atoms, Cv is 3/2R and Cp is 5/2R, but for diatomic ones, Cv is 5/2R and Cp is 7/2R
- Sun Feb 09, 2020 9:09 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Is heat capacity an extensive or intensive property?
- Replies: 2
- Views: 131
Is heat capacity an extensive or intensive property?
I found this previous post, https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=1396#p220853 , that says that heat capacity is an intensive property, however on the Wikipedia page for heat capacity, https://en.wikipedia.org/wiki/Heat_capacity , it says heat capacity is an extensive property. I'm so ...
- Sun Feb 09, 2020 9:02 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: First Law of Themordynamics
- Replies: 4
- Views: 277
Re: First Law of Themordynamics
They represent the same concept.
- Sun Feb 09, 2020 2:12 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Constant pressure
- Replies: 19
- Views: 723
Re: Constant pressure
Yes, constant external pressure.
- Sun Feb 02, 2020 12:20 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated vs Closed [ENDORSED]
- Replies: 34
- Views: 4461
Re: Isolated vs Closed [ENDORSED]
If it says it is insulated, we would assume that it is isolated. I don't think the wording of questions will be ambiguous. If it looks like the question is trying to imply that the system does not exchange energy (e.g. heat) with the environment, then it's probably trying to tell you that it is an i...
- Sat Feb 01, 2020 10:56 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed vs isolated systems
- Replies: 24
- Views: 959
Re: Closed vs isolated systems
Closed systems can exchange energy with the environment, but isolated systems cannot. So, like heat for example.
- Sat Feb 01, 2020 10:54 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed Systems
- Replies: 8
- Views: 450
Re: Closed Systems
Closed systems cannot exchange mass but they can exchange energy. Think of it as a metal can that's closed. The material inside cannot get out, but if you heat a flame under it, the matter inside will get hotter, thus energy is being exchanged. But if the system is isolated, it cannot exchange energ...
- Sat Feb 01, 2020 10:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Why does steam cause burns?
- Replies: 29
- Views: 1363
Re: Why does steam cause burns?
Steam has more energy than water, so the difference between the energy in steam and the energy of your skin is greater, and as such, when it comes into contact with you, it will transfer a correspondingly greater amount, leading to a more severe burn.
- Sat Feb 01, 2020 10:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: Open vs Isolated System
- Replies: 15
- Views: 1350
Re: Open vs Isolated System
words like "insulated" or "no exchange" or "closed to the environment" or any other words that indicate the system does not exchange matter or energy would be strong indications that the system is isolated, whereas words that indicate the system is able to exchange ener...
- Sun Jan 26, 2020 1:37 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Negative Square Root solving an ICE box
- Replies: 13
- Views: 614
Re: Negative Square Root solving an ICE box
If you got a negative number, you did something wrong.
- Sun Jan 26, 2020 1:37 am
- Forum: Phase Changes & Related Calculations
- Topic: Phase changes
- Replies: 7
- Views: 239
Re: Phase changes
Phase changes are literally just changes from different states of matter (solid, liquid, etc.). Temperature does not change, because the energy that is being added to the material is all going toward changing the phase (e.g from solid to liquid, the molecules are excited and they move faster so the ...
- Sun Jan 26, 2020 1:07 am
- Forum: Phase Changes & Related Calculations
- Topic: Steam vs Water
- Replies: 6
- Views: 239
Re: Steam vs Water
Steam does, because the difference in the energy of steam and your skin is greater than the difference between your skin and water, which being a liquid, does not have as much energy at the same temperature as steam does.
- Sun Jan 26, 2020 1:05 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: La Chatelier's Principle
- Replies: 8
- Views: 573
Re: La Chatelier's Principle
It will proceed in the other direction. For example, if products are added, the reaction will proceed toward the reactants, whereas if more reactants are added, the reaction will proceed toward the products.
- Sun Jan 26, 2020 1:04 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 7
- Views: 342
Re: Hess's Law
Hess's law states that the total enthalpy change during the complete course of a chemical reaction is the sum of its parts. Basically, it's stating that enthalpy can be added.
- Sun Jan 26, 2020 1:04 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 7
- Views: 342
Re: Hess's Law
Hess's law states that the total enthalpy change during the complete course of a chemical reaction is the sum of its parts. Basically, it's stating that enthalpy can be added.
- Sun Jan 19, 2020 8:04 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Solids and Liquids
- Replies: 6
- Views: 284
Re: Solids and Liquids
Because changes to their concentration are inconsequential for the rate of reaction. Solids just sit there, they don't really have a concentration because they don't mix with the solvent. Liquids are the solvent, so you assume that there will always be enough of it that any decrease will be insignif...
- Sun Jan 19, 2020 8:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5%
- Replies: 4
- Views: 195
Re: 5%
When using approximations for ICE tables, if you find that X is less than 5% of the initial concentration, then the approximation is valid.
- Sun Jan 19, 2020 8:00 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Temperature
- Replies: 5
- Views: 210
Re: Temperature
A change in temperature changes the direction of the reaction. For example, if a reaction is endothermic, and the temperature is increased, then K is pushed to the right. If the reaction is exothermic and the temperature is increased, then K is pushed to the left.
- Sun Jan 19, 2020 7:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K for Gases
- Replies: 12
- Views: 398
Re: K for Gases
Find Kp, because the pressure that a gas exerts is used to represent its concentration.
- Sun Jan 19, 2020 7:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When do we use the equilibrium sign?
- Replies: 7
- Views: 331
Re: When do we use the equilibrium sign?
Use it when there is not a complete reaction in one direction (there is a forward and reveres reaction happening at the same time). While most reactions are reversible (depending on the conditions they take place in), ones where we don't use the equilibrium sign usually occur under extreme conditions.
- Fri Jan 10, 2020 1:46 am
- Forum: Ideal Gases
- Topic: Ideal Gases
- Replies: 7
- Views: 541
Re: Ideal Gases
I do not think a perfectly ideal gas exists, but because the difference is negligible at higher temperatures, we just assume that they are so, to make calculations easier.
- Fri Jan 10, 2020 1:45 am
- Forum: Ideal Gases
- Topic: Understanding Q
- Replies: 13
- Views: 581
Re: Understanding Q
Yes you would, because the calculations for Q are the same as for K, except that the values used may be different.
- Fri Jan 10, 2020 1:43 am
- Forum: Ideal Gases
- Topic: Solving for K (coefficients)
- Replies: 11
- Views: 612
Re: Solving for K (coefficients)
No they do not, since multiplication exhibits commutative properties (a*b = b*a).
- Fri Jan 10, 2020 1:42 am
- Forum: Ideal Gases
- Topic: What is the Importance of homogeneous vs heterogeneous equilibria [ENDORSED]
- Replies: 12
- Views: 569
Re: What is the Importance of homogeneous vs heterogeneous equilibria [ENDORSED]
I believe the importance of homogeneous and heterogeneous equilibria is that for homogeneous equilibria, you do not have to worry about which of the materials are needed for the equilibria equation, whereas for heterogeneous you have to realize that solids and liquids are excluded.
- Fri Jan 10, 2020 1:41 am
- Forum: Ideal Gases
- Topic: PV=nRT equation manipulation
- Replies: 13
- Views: 758
Re: PV=nRT equation manipulation
We are manipulating the equation so that we can calculate the value that we want. For example, if we wanted concentration, which is n/V, we would move it to one side and everything else on the other side.
- Sat Dec 07, 2019 3:04 pm
- Forum: Lewis Acids & Bases
- Topic: Strong bases
- Replies: 2
- Views: 225
Strong bases
What are the strong bases that we will need to know for the final?
- Sat Dec 07, 2019 3:02 pm
- Forum: Lewis Acids & Bases
- Topic: neutralization
- Replies: 6
- Views: 601
Re: neutralization
As long as it's a base + acid = salt + H2O, then it is neutralization
- Sat Dec 07, 2019 3:00 pm
- Forum: Conjugate Acids & Bases
- Topic: Amphiprotic v. amphoteric
- Replies: 3
- Views: 424
Re: Amphiprotic v. amphoteric
Amphiprotic means it can donate or accept a proton, and amphoteric means it can act as a base or acid. All amphiprotic molecules are amphoteric, but not the other way around. An example of a amphoteric molecule that is not amphiprotic would be Al2O3. It does not contain any H's, but it can act as bo...
- Sat Dec 07, 2019 2:57 pm
- Forum: Naming
- Topic: (en), (dien), etc.
- Replies: 6
- Views: 394
Re: (en), (dien), etc.
Yes, one of the ta's yesterday said that we could use the abbreviations when naming them
- Sat Dec 07, 2019 2:57 pm
- Forum: General Science Questions
- Topic: Final Content
- Replies: 3
- Views: 454
Re: Final Content
Yes, but topics covered by the midterm will also be covered.
- Sat Nov 30, 2019 12:29 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Lewis Acid/Base
- Replies: 5
- Views: 246
Re: Lewis Acid/Base
Lewis acid means that this specific molecule will accept electrons, and a lewis base means that this molecule will donate electrons.
- Sat Nov 30, 2019 12:28 am
- Forum: Resonance Structures
- Topic: What is a Resonance "Structure"
- Replies: 12
- Views: 1084
Re: What is a Resonance "Structure"
Resonance structure refers to the bonds in that there are different bond combinations that are possible as lewis structures, BUT none of them are correct. Because electrons move around and are not actually held in straight line bonds, structures intermediate to the ones shown as lewis structures are...
- Sat Nov 30, 2019 12:26 am
- Forum: Naming
- Topic: Meaning of Cis and Trans
- Replies: 11
- Views: 957
Re: Meaning of Cis and Trans
Cis means that the molecule is symmetrical, with the same elements are on the same side. Trans means opposite, the elements are on different sides.
- Sat Nov 30, 2019 12:24 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: cis platinum
- Replies: 6
- Views: 443
Re: cis platinum
Basicallly, know that cis platinum is used as a chemotherapy drug to stop mitosis. It does this by replacing its two chlorines with two hydrogens, and then linking to two guanines. Because it is linked at two areas, it stops the two strands of dna from separating and keeps mitosis from happening, wh...
- Sat Nov 30, 2019 12:18 am
- Forum: Air Pollution & Acid Rain
- Topic: Clean Coal vs Dirty Coal?
- Replies: 16
- Views: 1503
Re: Clean Coal vs Dirty Coal?
The "clean"-ness of a coal refers to how high the carbon content is compared to sulfur content. If the coal has a really high carbon content and very low sulfur content, than it is "clean", whereas if it has a high sulfur content, then it is dirty coal
- Sat Nov 23, 2019 5:54 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: Best Approach to Find IMFs
- Replies: 11
- Views: 882
Re: Best Approach to Find IMFs
I think the best way is to look at the formula first. If it is definitely polar and does not have symmetry, you can probably assume that there are dipole forces. But of course, drawing a lewis structure would be safer. So draw the structure and see if there is symmetry when you are not sure.
- Sat Nov 23, 2019 5:51 pm
- Forum: Biological Examples
- Topic: Biological Examples
- Replies: 10
- Views: 542
Re: Biological Examples
I think there is a high chance that it will show up on the final, so you should definitely review any biological examples that come up in slides or learning material.
- Sat Nov 23, 2019 5:51 pm
- Forum: Hybridization
- Topic: hybridization
- Replies: 11
- Views: 586
Re: hybridization
Hybridization has to do with molecule shape. You can look at the shape of the molecule to derive the hybridization of the orbitals.
- Sat Nov 23, 2019 5:49 pm
- Forum: Hybridization
- Topic: Sigma and Pi Bonds
- Replies: 6
- Views: 465
Re: Sigma and Pi Bonds
The overlap of a pi bond is less than that of a sigma bond. However the sigma bond only overlaps at one area, whereas the pi bond overlaps at two. So because the pi bond overlaps at two areas, it cannot turn and thus keep the molecule in position.
- Sat Nov 23, 2019 5:47 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: IMF [ENDORSED]
- Replies: 6
- Views: 955
Re: IMF [ENDORSED]
dipole-dipole forces are when two polar molecules become attracted to each other. An induced dipole is when something is not normally polar, but becomes polar for a small instance because of the attraction of another molecule with a dipole
- Sat Nov 16, 2019 1:30 pm
- Forum: Dipole Moments
- Topic: Hydrogen bonds
- Replies: 17
- Views: 867
Re: Hydrogen bonds
Hydrogen bonds can only form between hydrogen and one of these three atoms.
- Sat Nov 16, 2019 1:30 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 3
- Views: 239
Re: Bond Angles
all bonds have the same "push", because the space they occupy is between atoms. Lone pairs cause more push because they can move freely on the outskirts of an atom, and thus it has a wider area of effect and a stronger push.
- Sat Nov 16, 2019 1:27 pm
- Forum: Dipole Moments
- Topic: London forces
- Replies: 9
- Views: 562
Re: London forces
London forces exist between all types of bonds and is universally present between all atoms. It is considered universal because no matter what types of molecules, london forces always exists between them.
- Sat Nov 16, 2019 1:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: All VSEPR structures or just ones from class?
- Replies: 11
- Views: 697
Re: All VSEPR structures or just ones from class?
Lavelle usually only makes us memorize the ones he teaches in class, so I think knowing only the ones from class will be sufficient for our next test. However, to be safe I would memorize all of them just in case.
- Sat Nov 16, 2019 1:25 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: Polar/non-polar
- Replies: 3
- Views: 144
Re: Polar/non-polar
You look at the bonds and symmetry. If the bonds are covalent with no dipole moments, then it is non-polar. If they are polar bonds but there is symmetry it is also non-polar. Only if both of these are false then can it be polar.
- Sat Nov 09, 2019 7:10 pm
- Forum: Bond Lengths & Energies
- Topic: Shape of Molecules and bond strength
- Replies: 5
- Views: 175
Shape of Molecules and bond strength
Why does the shape of a molecule contribute to how strong the bond is between it and other molecules?
- Sat Nov 09, 2019 7:07 pm
- Forum: Bond Lengths & Energies
- Topic: Hydrogen Bonding melting point
- Replies: 3
- Views: 149
Re: Hydrogen Bonding melting point
Basically, higher melting point means that intermolecular forces are stronger, so molecules aren't as easily separated. Hydrogen bonds is a very strong attraction between different molecules, and because of hydrogen bonds, certain molecules have higher melting points than you would expect otherwise.
- Sat Nov 09, 2019 7:06 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 vs London
- Replies: 4
- Views: 328
Re: Dipole-Dipole vs London
London dispersion forces occur in all molecules. It refers to how, when electrons are moving randomly around the nucleus, there will always be an ebb and flow in how negatively/positively charged a particular region of that atom is. These slight imbalances that occur attract each other, so all atoms...
- Sat Nov 09, 2019 7:04 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polar Covalent VS Ionic
- Replies: 11
- Views: 688
Re: Polar Covalent VS Ionic
If the difference in electronegativity is greater than two, then it is ionic. If it is not ionic, look at the difference in charge between the atoms to determine if it is polar.
- Sat Nov 09, 2019 7:02 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: 3
- Views: 122
Re: Hydrogen Bonding
Adding on to what everyone else mentioned, hydrogen atoms are small in size, and because distance is inversely proportional to the strength of a bond, this contributes to the strength of the hydrogen bond.
- Sat Nov 02, 2019 1:47 am
- Forum: Properties of Light
- Topic: Speed of light
- Replies: 13
- Views: 384
Re: Speed of light
Electromagnetic radiation travels at the speed of light, therefore we use the speed of light to calculate it. Light is a form of electromagnetic radiation, and the speed of light is really the speed of all these EM waves.
- Sat Nov 02, 2019 1:45 am
- Forum: Dipole Moments
- Topic: induced dipole
- Replies: 4
- Views: 183
Re: induced dipole
An induced dipole is when an atom that is not usually able to form a dipole becomes a dipole because of interactions with neighboring atoms.
- Sat Nov 02, 2019 1:43 am
- Forum: Lewis Structures
- Topic: Electrons Moving Around
- Replies: 3
- Views: 202
Re: Electrons Moving Around
If they form ions, then yes the electron "leaves". However if it's a covalent bond, then no, the electrons don't leave their home atoms, instead it creates kind of a "shared" orbital between the two atoms.
- Sat Nov 02, 2019 1:41 am
- Forum: Lewis Structures
- Topic: Compound Names
- Replies: 3
- Views: 180
Re: Compound Names
According to a TA, they will most likely not give us just the name and ask us to find the formula from that. They said that even if they did, it would be an easy formula.
- Sat Nov 02, 2019 1:04 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: General Question about Orbital... Filling..?
- Replies: 5
- Views: 190
Re: General Question about Orbital... Filling..?
They are different ways of writing it, but Lavelle specifically told us in class to write it [Ar] 3d2, 4s2. Whether or not he takes off points if you write it the other way I don't know, but definitely write it this way.
- Sat Oct 26, 2019 9:59 pm
- Forum: Lewis Structures
- Topic: Covalent vs Ionic
- Replies: 2
- Views: 95
Re: Covalent vs Ionic
Ionic bonds are much stronger than covalent bonds. This is because ionic bonds involve the complete transfer of electrons so the electrostatic forces are stronger.
- Sat Oct 26, 2019 9:56 pm
- Forum: Properties of Electrons
- Topic: Mass of an Electron
- Replies: 14
- Views: 608
Re: Mass of an Electron
The mass of an electron is constant. While the orbit they take can change between elements and orbital levels, electrons are still electrons and their mass remains constant.
- Sat Oct 26, 2019 9:53 pm
- Forum: Sigma & Pi Bonds
- Topic: Double bond
- Replies: 15
- Views: 621
Re: Double bond
Two things to pay attention to are formal charge and octets. Most elements want to have a full shell of valence electrons, so try to make sure that they all have 8 electrons around them. Next is to pay attention to the formal charge. If by forming a double bond, the formal charge is closer to 0, the...
- Sat Oct 26, 2019 9:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration Notation
- Replies: 5
- Views: 267
Re: Electron Configuration Notation
Although they are both correct, you should use the way Dr.Lavelle wants us to do it. Using 3d and 4s as an example, he wants us to do it this way to emphasize that when the 3d orbital is used, 3d actually has a lower energy level than 4s, even though the 4s is filled first.
- Sat Oct 26, 2019 9:43 pm
- Forum: Lewis Structures
- Topic: Drawing Lewis Structures
- Replies: 8
- Views: 269
Re: Drawing Lewis Structures
Hydrogen is never used as the central atom.
- Sat Oct 19, 2019 7:12 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Why 3d before 4s
- Replies: 2
- Views: 170
Why 3d before 4s
Why does Dr.Lavelle want us to put 3d before 4s when we are writing the electron configurations?
- Sat Oct 19, 2019 7:06 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Tips for the Midterm
- Replies: 10
- Views: 392
Re: Tips for the Midterm
Do all the homework questions and make sure you understand the concepts that were mentioned and the relevant equations.
- Sat Oct 19, 2019 7:06 pm
- Forum: Properties of Light
- Topic: What are the units of hertz
- Replies: 41
- Views: 2263
Re: What are the units of hertz
The units for hertz is cycles per second, but the cycles can refer to a number of different cycles so it's -s.
- Sat Oct 19, 2019 6:33 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 4s vs. 3d
- Replies: 6
- Views: 244
Re: 4s vs. 3d
Strictly speaking, 3d is higher in energy than 4s only if there are no electrons in 3d. When the 3d starts filling up with electrons, the relative energies fluctuate and 4s ends up with a higher energy level as 3d becomes more filled.
- Sat Oct 19, 2019 6:27 pm
- Forum: Properties of Light
- Topic: Unit Conversions
- Replies: 6
- Views: 333
Re: Unit Conversions
The way I do it is I convert it to meters first before finishing the calculations. Using your example, lets assume that we have 100 nm. Then 100 nm x (1 m/10^9 nm) x (10^12 pm/1 m) = 100,000 pm. Although this may take longer than converting directly, it makes sure that your answer is correct.
- Fri Oct 11, 2019 1:41 pm
- Forum: SI Units, Unit Conversions
- Topic: Showing work/ rearranging equations
- Replies: 8
- Views: 784
Re: Showing work/ rearranging equations
I think as long as your thought process is clear and they can tell what you were trying to do through your work, you should be good.
- Fri Oct 11, 2019 1:40 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Accuracy and Precision
- Replies: 8
- Views: 453
Re: Accuracy and Precision
This is just a fundamental topic that has more to do with labs. Precision does have a connection to significant figures though. Specifically, the more sig figs your data has, the more precise your answer.
- Fri Oct 11, 2019 1:38 pm
- Forum: Properties of Electrons
- Topic: Energy
- Replies: 6
- Views: 351
Re: Energy
Yes and yes. If the energy is not in those specific quanta amounts, it will not absorb it.
- Fri Oct 11, 2019 1:36 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Theoretical vs. Actual Yield
- Replies: 38
- Views: 14242
Re: Theoretical vs. Actual Yield
theoretical yield is the yield that will be obtained if all of the given reactants are used to completion and everything goes perfectly. However during real experiments, more often than not, things happen; the product sticks to the beaker, escapes into the atmosphere or something, and the yield obta...
- Fri Oct 11, 2019 1:33 pm
- Forum: Properties of Light
- Topic: Energy Levels and Color of light
- Replies: 4
- Views: 628
Re: Energy Levels and Color of light
Color of light is decided by the wavelength of the light. If the electron loses energy and releases that energy as a photon, the wavelength of the photon decides the color of the light i think.
- Wed Oct 02, 2019 11:51 pm
- Forum: Empirical & Molecular Formulas
- Topic: Question about Theoretical Yield
- Replies: 8
- Views: 494
Re: Question about Theoretical Yield
There is no difference between calculating theoretical yield with grams versus theoretical yield with moles. The only difference would be what units your answer is in. Something to always be careful about is what units the question wants your answer to be in. If you find that your units are differen...