Search found 111 matches
- Sun Mar 15, 2020 1:18 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Athena
- Replies: 34
- Views: 3035
Re: Athena
Dr. Lavelle, Thank you for being a great chemistry professor and for always supporting your students. I used to hate chemistry in high school because my teacher wasn't so great. But, thanks to you, I found a new interest in chemistry. It was a pleasure to be your student for two quarters. I hope you...
- Thu Mar 12, 2020 11:12 am
- Forum: Second Order Reactions
- Topic: Finding out order
- Replies: 22
- Views: 950
Re: Finding out order
Yes, the units can be used to determine the order of the reaction. The way I think about it is, you start out with the units M/s for a zero-order reaction and then you keep dividing by M for each reaction after. For instance, the units for a first-order reaction are 1/s and the units for a second-or...
- Thu Mar 12, 2020 11:07 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 12
- Views: 769
Re: Final
The exam will be submitted electronically. Dr. Lavelle will definitely email us to let us know how to turn it in. In his past emails, he said that he will post the final exam on his class website.
- Thu Mar 12, 2020 11:05 am
- Forum: Second Order Reactions
- Topic: Graphs
- Replies: 9
- Views: 727
Re: Graphs
I suggest looking at the email that Dr. Lavelle sent us through email titled "Week 10 Review." It has the graphs for each order. Hope this helps!
- Tue Mar 10, 2020 11:19 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Difference between catalyst and intermediate
- Replies: 9
- Views: 625
Re: Difference between catalyst and intermediate
An intermediate is always produced and then consumed. Meanwhile, a catalyst is consumed then reproduced.
- Mon Mar 09, 2020 9:50 pm
- Forum: General Rate Laws
- Topic: Equations
- Replies: 5
- Views: 411
Equations
Will we have to know how to derive the zero-, first-, and second-order equations, along with the half-life equations on the final?
- Wed Mar 04, 2020 10:48 am
- Forum: Balancing Redox Reactions
- Topic: Oxidation Number
- Replies: 2
- Views: 234
Re: Oxidation Number
Adding to this, the oxidation number of ozone (O3) is 0.
- Wed Mar 04, 2020 10:27 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram
- Replies: 3
- Views: 333
Re: Cell Diagram
You add Pt(s) to the side of the cell diagram (either to the anode or cathode side) that lacks a solid metal conductor.
- Tue Mar 03, 2020 6:02 pm
- Forum: Van't Hoff Equation
- Topic: Equation Sheet
- Replies: 18
- Views: 1017
Re: Equation Sheet
It is not. You should know how to derive it. If you don't know, I suggest just memorizing it.
- Tue Mar 03, 2020 6:00 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum and Granite
- Replies: 4
- Views: 331
Re: Platinum and Granite
I suggest always using platinum because using granite is not common. If we have to use granite, I feel like we would be specifically told to do so.
- Tue Mar 03, 2020 5:57 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equation
- Replies: 3
- Views: 353
Re: Nernst Equation
It doesn't really matter whether you use the ln Q or log Q equation. Some people prefer the log Q equation because on the equations sheet, you are given 0.05916V/n and you do not have to calculate R*T/nF, which you have to calculate with the ln Q equation.
- Fri Feb 28, 2020 4:42 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Spontaneity
- Replies: 12
- Views: 875
Re: Spontaneity
If you are observing a galvanic cell, you can also tell if a reaction is spontaneous if E°cell is positive.
- Fri Feb 28, 2020 12:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Is it spontaneous?
- Replies: 4
- Views: 315
Re: Is it spontaneous?
When E°cell=0, the reaction is at equilibrium and delta G=0. This occurs when a battery is dead.
- Thu Feb 27, 2020 9:03 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: When to apply Pt into cell diagrams
- Replies: 9
- Views: 499
Re: When to apply Pt into cell diagrams
You would apply Pt into cell diagrams when there is not another solid metal electrode.
- Thu Feb 27, 2020 12:49 am
- Forum: Balancing Redox Reactions
- Topic: Coefficient consideration
- Replies: 4
- Views: 310
Re: Coefficient consideration
You do have to consider the coefficient when determining the overall charge of a molecule. The charge of 5Cu2+ (charge is 10+) is not the same as the charge of Cu2+ (charge is 2+).
- Sat Feb 22, 2020 10:41 am
- Forum: Balancing Redox Reactions
- Topic: Charge of oxygen
- Replies: 15
- Views: 711
Re: Charge of oxygen
The oxidation number of oxygen is usually 2-, except in peroxides where it is 1- and ozone where it is 0.
- Sat Feb 22, 2020 10:40 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: more than 2 cells
- Replies: 3
- Views: 289
Re: more than 2 cells
It is possible to have more than two galvanic cells. I believe that they would work the same way in which the electrons move from the anode to the cathode. I am not sure about the specific details.
- Sat Feb 22, 2020 10:29 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Pt
- Replies: 7
- Views: 442
Re: Pt
As mentioned, Pt stands for platinum. It is used as an inert conductor to transfer electrons when a half-reaction has no conducting solids. Platinum is written on the outermost part of the cathode side because it is a solid.
- Wed Feb 19, 2020 8:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Dead Battery
- Replies: 6
- Views: 379
Dead Battery
Can someone explain when a battery is dead in terms of what we discussed in lecture today? Thank you.
- Wed Feb 19, 2020 8:43 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpies of formation
- Replies: 2
- Views: 218
Re: Enthalpies of formation
Most enthalpies of formation are negative because energy is released when bonds are formed, thus, the reaction is exothermic.
- Wed Feb 19, 2020 8:24 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Midterm Q6B
- Replies: 5
- Views: 489
Re: Midterm Q6B
For this question, you have to look at the equation ∆G= ∆H-T∆S. ∆G= ∆H when ∆S is approximately 0. In answer a., the change in entropy is approximately zero because there are no phase changes. The reactants and the products are both all solids.
- Tue Feb 11, 2020 10:25 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy and Heat
- Replies: 4
- Views: 406
Re: Enthalpy and Heat
Enthalpy (ΔH) is the measure of heat released or absorbed at a constant pressure. q is just heat under any conditions. ΔH would be equal to q only when the heat is released or absorbed at a constant pressure.
- Tue Feb 11, 2020 12:12 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: spontaneity
- Replies: 7
- Views: 350
Re: spontaneity
If the ΔG is negative, then the reaction is spontaneous and favors the forward process.
- Tue Feb 11, 2020 12:10 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: delta U = q + w
- Replies: 6
- Views: 378
Re: delta U = q + w
If work is done on the system by the surroundings, then work is positive. If work is done by the system onto the surroundings, then work is negative. This is because when work is done by the system, the system loses energy.
- Tue Feb 11, 2020 12:05 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Go=0
- Replies: 7
- Views: 376
Re: Go=0
In lecture today we learned that ΔG is zero at a reaction's boiling point.
- Tue Feb 11, 2020 12:01 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: isothermal
- Replies: 2
- Views: 77
Re: isothermal
Yes, using the equation ΔU=(3/2)nRΔT, you can see that if ΔT is zero, so is ΔU.
- Thu Feb 06, 2020 1:45 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Thermodynamics
- Replies: 6
- Views: 291
Re: Thermodynamics
When heat is transferred from the system and work is done by the system, both heat and work are negative. This is because when heat is transferred from the system, the system loses heat (hence the negative q). When work is done by the system, the system is losing energy (hence work is negative).
- Thu Feb 06, 2020 1:41 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: -qsystem=qsurroundings
- Replies: 2
- Views: 111
-qsystem=qsurroundings
When I am doing calculations, I have a bit of trouble determining when to apply the "-qsystem=qsurroundings." How can you determine when to use this in a problem? Does anyone have any tips?
- Tue Feb 04, 2020 4:40 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 1 Distribution
- Replies: 9
- Views: 298
Re: Test 1 Distribution
Most likely not. We don't get distribution curves for tests.
- Tue Feb 04, 2020 4:37 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: HW 4A.13
- Replies: 1
- Views: 100
Re: HW 4A.13
It is negative because the reaction is exothermic. The reaction is exothermic because heat is negative (reaction releases heat).
- Tue Feb 04, 2020 4:22 pm
- Forum: Calculating Work of Expansion
- Topic: second equation
- Replies: 8
- Views: 215
Re: second equation
Unless asked to derive the equation, you would just use the -nRTln(v2/v1).
- Wed Jan 29, 2020 7:19 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Increasing energy in an open system
- Replies: 7
- Views: 234
Re: Increasing energy in an open system
As discussed today in lecture, you can increase the energy of an open system by doing one of the following:
- adding or removing a substance
- heating or cooling the system
- doing work on the system or letting the system do work on its surroundings
- adding or removing a substance
- heating or cooling the system
- doing work on the system or letting the system do work on its surroundings
- Wed Jan 29, 2020 7:14 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: memorize
- Replies: 6
- Views: 239
Re: memorize
I would memorize the heat capacity of water, but other capacities most likely will be given in the equations sheet.
- Wed Jan 29, 2020 7:11 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat, Temperature, Enthalpy
- Replies: 4
- Views: 128
Heat, Temperature, Enthalpy
Can someone explain the difference between heat, temperature, and enthalpy? Thank you!
- Wed Jan 29, 2020 4:31 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Endothermic vs Exothermic
- Replies: 10
- Views: 509
Re: Endothermic vs Exothermic
This is correct. A negative value of q indicates that the system lost heat. Thus, the reaction is exothermic. A positive value of q indicates that the system gained heat. Thus, the reaction is endothermic.
- Tue Jan 28, 2020 10:24 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed vs isolated systems
- Replies: 24
- Views: 814
Re: Closed vs isolated systems
Think of a closed system as a cup of coffee with a lid. It can exchange energy with its surroundings in the form of heat but cannot exchange matter because the lid is closed. Think of an isolated system, or something close to it, as a sealed hydro flask. You cannot exchange energy (hydro flasks esse...
- Wed Jan 22, 2020 7:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ice Box Question
- Replies: 2
- Views: 97
Re: Ice Box Question
Usually, we do subtract x from the reactants because the reactants are being used up. But, if the problem explicitly states that the products decreased in concentration or pressure, then you would subtract x from the products.
- Wed Jan 22, 2020 7:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong Acids and Bases in Water
- Replies: 1
- Views: 74
Re: Strong Acids and Bases in Water
Strong acids and bases dissociate completely. Thus, if you know the concentration of a strong acid or base, you can find the hydronium and hydroxide concentration with molar ratios. You can then use this to find the pH or the pOH. For instance, if a problem says that you have 0.138 M HCl, then you k...
- Wed Jan 22, 2020 7:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Autoprotolysis
- Replies: 1
- Views: 84
Re: Autoprotolysis
The reaction is endothermic because heat is required in order to break the hydrogen bonds between two water molecules.
- Wed Jan 22, 2020 7:27 pm
- Forum: General Science Questions
- Topic: Test 1: Sig Figs
- Replies: 7
- Views: 346
Re: Test 1: Sig Figs
I am not sure if they count, but I would suggest knowing how they work. If pH=5.1 and you have to find the hydronium concentration, there are two significant figures total in the pH. Thus, you would put two numbers after the decimal point in your hydronium concentration answer. If you are asked to f...
- Wed Jan 22, 2020 7:21 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Exothermic vs. Endothermic reactions
- Replies: 12
- Views: 914
Re: Exothermic vs. Endothermic reactions
It is possible. All I suggest knowing is that when delta H is positive, the reaction is endothermic and when delta H is negative, the reaction is exothermic.
- Thu Jan 16, 2020 10:25 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quadratic
- Replies: 6
- Views: 158
Re: Quadratic
It will be given on tests. If you look at the "constants and equations" section on his website, you will see that the quadratic equation is given.
- Wed Jan 15, 2020 7:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.39
- Replies: 2
- Views: 128
Re: 5.39
I also came across this and was confused. I am sure it is just a typo. I would suggest doing the calculation with the value given in the textbook for extra practice.
- Wed Jan 15, 2020 7:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong acids/weak acids
- Replies: 3
- Views: 142
Re: Strong acids/weak acids
Strong acids do have a Ka value. They have large Ka values because the higher the Ka, the more the acid dissociates. They have low pKa values.
- Tue Jan 14, 2020 2:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Autoprolysis
- Replies: 9
- Views: 646
Re: Autoprolysis
Adding to this conversation, what does amphiprotic mean again?
- Tue Jan 14, 2020 2:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE charts on tests/exams
- Replies: 8
- Views: 236
Re: ICE charts on tests/exams
Since we spent almost an entire lecture learning about ice charts, it is safe to say that we will have to include them on exams as part of showing our work.
- Sat Jan 11, 2020 10:16 am
- Forum: Ideal Gases
- Topic: Solids and Liquids [ENDORSED]
- Replies: 10
- Views: 518
Re: Solids and Liquids [ENDORSED]
It does not make sense for solids to have a concentration since the units for concentration are mol/L. For liquids, the change in concentration is insignificant because the change is very small.
- Thu Jan 09, 2020 10:30 pm
- Forum: Ideal Gases
- Topic: 5G1 true/false
- Replies: 8
- Views: 256
Re: 5G1 true/false
Instead of looking at K as Kc look at it as Kp. Kp= (partial pressure of products) / (partial pressure of reactants) according to this equation, an increase in the partial pressure of reactants would lead to a decrease in the equilibrium constant instead of an increase in the equilibrium constant, ...
- Thu Jan 09, 2020 10:27 pm
- Forum: Ideal Gases
- Topic: 5G1 true/false
- Replies: 8
- Views: 256
Re: 5G1 true/false
Your reasoning that "if there is higher pressure of reactant, it will shift towards product" is correct. However, this does not mean that K will change. Here, only Q is changing because initially Q<K. K is not changing. This is because the temperature is constant. Only when the temperature...
- Wed Jan 08, 2020 11:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework Question 5I.13
- Replies: 2
- Views: 120
Homework Question 5I.13
In an experiment, 2.0 mmol Cl2(g) was sealed into a reaction vessel of volume 2.0 L and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 5G.2 to calculate the equilibrium composition of the mixture. (b) If 2.0 mmol F2 was placed into the reaction vessel instead...
- Wed Jan 08, 2020 12:03 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reverse reaction
- Replies: 6
- Views: 221
Re: Reverse reaction
The reverse reaction occurs when Q>K. This occurs when there is an abundance of products and not enough reactants.
- Tue Jan 07, 2020 1:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Keq vs Kc
- Replies: 6
- Views: 404
Re: Keq vs Kc
Also relevant to this discussion is how Kc is different than Kp. Kp is the equilibrium constant found using partial pressures. The method of calculating Kp is essentially the same as Kc, except Kp is calculated by the partial pressure of products/the partial pressure of the reactants.
- Tue Jan 07, 2020 12:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Table Variables
- Replies: 2
- Views: 78
Re: ICE Table Variables
I would use the variable x for the change concentration. Putting the variable x for the change concentration makes it clearer and easier to find the value of x as opposed to putting numbers for the change concentration.
- Wed Dec 04, 2019 10:34 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Drawing structures on the final
- Replies: 3
- Views: 183
Re: Drawing structures on the final
I don't believe that we have to know how to draw coordination compounds or chelating coordination compounds because it was not thoroughly discussed in the lecture. However, make sure you thoroughly understand the concepts of each and make sure you know how to draw cisplatin, EDTA, myoglobin, ethylen...
- Wed Dec 04, 2019 10:29 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid or Base
- Replies: 2
- Views: 173
Re: Acid or Base
SO3 is a nonmetal oxide and nonmetal oxides are acidic
- Wed Dec 04, 2019 10:24 am
- Forum: Bronsted Acids & Bases
- Topic: Neutralizations
- Replies: 3
- Views: 234
Re: Neutralizations
In a neutralization reaction, acids and bases always produce salt and water.
- Wed Dec 04, 2019 10:14 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 6C 21 part b
- Replies: 2
- Views: 97
Re: 6C 21 part b
Formic acid is stronger than acetic acid because acetic acid has a CH3 that is e- donating. This means that CH3 contributes electron density to the O-H bond. This makes it harder to remove the H. Thus it is weaker acid compared to formic acid.
- Wed Dec 04, 2019 10:05 am
- Forum: Biological Examples
- Topic: Cisplatin
- Replies: 6
- Views: 420
Re: Cisplatin
Unlike trans-diamine-dichloro-platinum, Cisplatin has two Cls on the same side of the molecule that allows the Cls to bind to the same DNA strand to form 2 bonds. This blocks the enzymes used in DNA replication from replicating the DNA strand. Thus, it blocks DNA replication.
- Wed Dec 04, 2019 9:59 am
- Forum: Properties of Light
- Topic: Light as a Wave
- Replies: 8
- Views: 562
Re: Light as a Wave
Light has wave-like properties all the time, along with particle-like properties.
- Mon Nov 25, 2019 11:43 am
- Forum: Hybridization
- Topic: When does hybridization occur?
- Replies: 7
- Views: 418
Re: When does hybridization occur?
Hybridization doesn't always occur when forming bonds. It only occurs when an atom needs to form more bonds than it would be able to in a ground state.
- Mon Nov 25, 2019 11:41 am
- Forum: Naming
- Topic: Correct naming conventions
- Replies: 5
- Views: 306
Re: Correct naming conventions
You add the suffix -ate to the metal name in a coordination compound when the net coordination compound has a net negative charge.
- Mon Nov 25, 2019 11:29 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: Hydrogen Bonding Sites
- Replies: 2
- Views: 143
Re: Hydrogen Bonding Sites
We can determine the number of hydrogen bonding sites between two molecules if there is an F, O, or N with an available lone pair. A hydrogen must be bonded to a F, O, or N.
- Mon Nov 25, 2019 9:28 am
- Forum: Hybridization
- Topic: Sigma and Pi Bonds
- Replies: 5
- Views: 275
Re: Sigma and Pi Bonds
Sigma bonds are also made from hybridized orbitals, whereas pi bonds are made only from leftover p orbitals.
- Mon Nov 25, 2019 9:21 am
- Forum: Naming
- Topic: Coordination shape
- Replies: 3
- Views: 125
Re: Coordination shape
Lavelle did not go into too much depth about this but I believe that you have to draw the Lewis structure. If the molecule has a tetrahedral shape, it is a tetrahedral complex. If the molecule has a square planar shape, it is a square planar complex.
- Sun Nov 24, 2019 1:43 pm
- Forum: Hybridization
- Topic: d-orbitals
- Replies: 7
- Views: 619
Re: d-orbitals
D-orbitals do get involved in hybridization. This is why there are sp^3d orbitals and sp^3d^2 orbitals.
- Wed Nov 20, 2019 10:09 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs for AX4E
- Replies: 3
- Views: 180
Re: Lone Pairs for AX4E
When the lone pair is in the equatorial plane, it is only perpendicular to two atoms. If the lone pair was in the axial plane, it would be perpendicular to three atoms. Therefore, having a lone pair in the equatorial plane would minimize the repulsions created by the lone pair.
- Wed Nov 20, 2019 9:38 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: cancelling dipoles
- Replies: 2
- Views: 176
Re: cancelling dipoles
You are correct in that the dipole moments only cancel for a tetrahedral if all the atoms bonded to the central atom are the same. This would make the molecule nonpolar. If one atom is different, the dipole moments do not cancel and the molecule is polar. However, it is possible for different atoms ...
- Wed Nov 20, 2019 9:31 am
- Forum: Dipole Moments
- Topic: Hydrogen Bonds
- Replies: 3
- Views: 108
Re: Hydrogen Bonds
This is correct. But, you also have to remember that F, O, and N also must have an available lone pair in order to be able to form a hydrogen bond.
- Tue Nov 19, 2019 10:36 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: kJ/mol
- Replies: 1
- Views: 116
Re: kJ/mol
I do not believe that we need to know these exact values. Just know the strength of each intermolecular force in comparison with other intermolecular forces. You should know that ion-ion forces are the strongest followed by hydrogen bonds, ion-dipole forces, dipole-dipole forces, and london dispersi...
- Tue Nov 19, 2019 10:32 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Figuring Out Bond Angle
- Replies: 3
- Views: 180
Re: Figuring Out Bond Angle
If the central atom has lone pairs, it will cause more electron-electron repulsion, which will result in a molecule having a bond angle that is smaller than usual (i.e. less than 120 degrees). You can think of this as if the electrons are "pushing away" the other bonds, which results in a ...
- Sun Nov 17, 2019 12:32 am
- Forum: Electronegativity
- Topic: Symbols for partial charge
- Replies: 4
- Views: 4358
Re: Symbols for partial charge
The symbols represent partial charge. The negative partial charge goes on the most electronegative atom in a molecule, while the positive charge goes on the other atom. The dipole moments, which represent the arrows used, point from a positive partial charge to a negative partial charge (towards the...
- Thu Nov 14, 2019 12:19 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: H-bonds
- Replies: 4
- Views: 205
Re: H-bonds
Hydrogen bonds do have dipole moments because they typically form when a hydrogen atom bonds to a highly electronegative atom (F,O,N). When bonded to these specific highly electronegative atoms, the hydrogen bonds will have a dipole moment.
- Wed Nov 13, 2019 10:13 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorization
- Replies: 15
- Views: 947
Re: Memorization
We do have to memorize the different shapes. However, Lavelle said that we are not required to memorize all of the bond angles as we will never be specifically asked to state them. The main thing that he wants us to remember are the shapes.
- Wed Nov 13, 2019 9:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Intermolecular Forces
- Replies: 2
- Views: 160
Intermolecular Forces
If given a molecule, how can you determine whether it has dipole-dipole interactions, dipole-induced dipole interactions, or induced dipole-induced dipole interactions?
- Wed Nov 13, 2019 9:20 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: Determining Polarity
- Replies: 5
- Views: 387
Re: Determining Polarity
In order to determine if a molecule is polar, you have to look at the shape and the differences in electronegativity. There is no cutoff in electronegativity. If the dipole moments all cancel, the molecule is nonpolar. If the dipole moments do not cancel, the molecule is polar.
- Mon Nov 11, 2019 8:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Interactions between Ions and Molecules
- Replies: 1
- Views: 98
Interactions between Ions and Molecules
What is the difference between ion-ion, ion-dipole, dipole-dipole, and dipole-induced dipole interactions?
- Mon Nov 11, 2019 8:37 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Induced dipole-induced dipole interactions
- Replies: 2
- Views: 75
Induced dipole-induced dipole interactions
How does induced dipole-induced dipole interactions relate to polarizability and electron distortion?
- Mon Nov 11, 2019 8:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Hydrogen Bonding
- Replies: 3
- Views: 123
Hydrogen Bonding
How does hydrogen bonding affect the melting points of compounds?
- Tue Nov 05, 2019 7:04 pm
- Forum: Electronegativity
- Topic: Homework Question 2D.5 Part a
- Replies: 2
- Views: 94
Homework Question 2D.5 Part a
For each pair, determine which compound has bonds with greater ionic character: (a) HCl or HI; (b) CH4 or CF4; (c) CO2 or CS2?
For part a, I was wondering why HI has a lower ionic character than HCl. I am just confused as to why HCl has a larger difference in electronegativity than HI.
For part a, I was wondering why HI has a lower ionic character than HCl. I am just confused as to why HCl has a larger difference in electronegativity than HI.
- Mon Nov 04, 2019 11:52 pm
- Forum: Lewis Structures
- Topic: Valence Electrons in D Subshell
- Replies: 5
- Views: 152
Valence Electrons in D Subshell
How do you determine the number of valence electrons in the d subshell? On A.1 part c, they asked for the number of valence electrons in Manganese and the answer was 7. How did they get to this answer?
- Mon Nov 04, 2019 9:47 am
- Forum: Octet Exceptions
- Topic: octet exceptions
- Replies: 11
- Views: 552
Re: octet exceptions
Boron is also an exception to the octet rule as it can be content with 6 valence electrons, instead of an octet.
- Sun Nov 03, 2019 1:25 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Which equations can be used for what topics
- Replies: 2
- Views: 82
Re: Which equations can be used for what topics
E=hv is used for the energy of a photon, or in this case, electromagnetic radiation.
- Sun Nov 03, 2019 1:19 am
- Forum: Dipole Moments
- Topic: Dipole Moments
- Replies: 3
- Views: 82
Dipole Moments
Can someone please explain to me what dipole moments are and what they have to do with electronegativity?
- Thu Oct 31, 2019 1:40 am
- Forum: Student Social/Study Group
- Topic: Equation sheet
- Replies: 1
- Views: 108
Re: Equation sheet
Here's the link to the constants and equations sheet that Lavelle has on his website: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/constants_equations.pdf If you cannot access the sheet through this link, you can find it on Lavelle's Chem14A classroom page. It is under the title...
- Wed Oct 30, 2019 9:36 am
- Forum: Trends in The Periodic Table
- Topic: Summary of Periodic Trends [ENDORSED]
- Replies: 2
- Views: 112
Re: Summary of Periodic Trends [ENDORSED]
I find it useful to remember that most periodic trends increase going upper right on the periodic table. This includes, ionization energy, electron affinity, and electronegativity. The only periodic trend that increases to the lower left is atomic radii and ionic radii.
- Wed Oct 30, 2019 9:32 am
- Forum: Resonance Structures
- Topic: Delocalization vs. Resonance
- Replies: 8
- Views: 2905
Re: Delocalization vs. Resonance
A molecule with resonance refers to the fact that it has multiple bonds that can be placed in different locations within the molecule, without moving the individual atoms in the molecule. When a molecule has resonance, the electrons aren't localized at one particular atom, but rather they are deloca...
- Sat Oct 26, 2019 10:37 pm
- Forum: Trends in The Periodic Table
- Topic: atomic Radii
- Replies: 11
- Views: 399
Re: atomic Radii
This is correct. The addition of an electron adds more electrons to the outermost shell. This increases the radius because there are now more electrons farther away from the nucleus.
- Sat Oct 26, 2019 10:35 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Ms and ML
- Replies: 6
- Views: 1957
Re: Ms and ML
I believe that you have ms and ml confused. Ms, which stands for the spin magnetic quantum number, is always either +1/2 or -1/2. +1/2 indicates that the electron's spin is up. -1/2 indicates that the electron's spin is down. Ml stands for the magnetic quantum number and refers to the orientation of...
- Sat Oct 26, 2019 10:25 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Shorthand Notation
- Replies: 4
- Views: 235
Re: Shorthand Notation
I believe that for most electron configurations, we will have to write the entire configuration. However, if an element has an excessively long electron configuration, such as Strontium, we most likely will be able to use the shorthand notation.
- Fri Oct 25, 2019 1:13 am
- Forum: Administrative Questions and Class Announcements
- Topic: Powerpoint Slides
- Replies: 5
- Views: 147
Re: Powerpoint Slides
Unfortunately, we do not. Luckily, professor Lavelle gives us enough time in class to take notes, and he doesn't rush us.
- Fri Oct 25, 2019 1:11 am
- Forum: Ionic & Covalent Bonds
- Topic: Electron Affinity
- Replies: 5
- Views: 282
Re: Electron Affinity
Why does electron affinity increase as we go towards the noble gasses? Electron affinity increases as we go towards the noble gases because the elements near the noble gases have the tendency to gain an electron due to their higher nuclear charge. In order for these elements to fill their shells, i...
- Tue Oct 22, 2019 11:00 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configurations
- Replies: 4
- Views: 188
Re: Electron Configurations
As to your question on how many electrons will fit into a specific orbital, each orbital consists of two electrons. There is one s-orbital, thus there are 2 electrons in the s-sublevel. There are 3 p-orbitals, thus there are 6 electrons in the p-sublevel (3 p-orbitals* 2 e- per orbital). There are a...
- Tue Oct 22, 2019 10:50 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: s, p, d, f orbitals
- Replies: 15
- Views: 721
Re: s, p, d, f orbitals
As to the first part of your question, 3d orbitals have slightly higher energy than 4s orbitals, thus, the 4s orbitals get filled first. This is only true if there are no electrons in the 3d orbitals. If the 3d orbitals are filled, then the 4s orbitals will be higher in energy.
- Wed Oct 16, 2019 1:01 pm
- Forum: Properties of Electrons
- Topic: Properties of P momentum
- Replies: 3
- Views: 207
Re: Properties of P momentum
p = mv (v is the greek letter nu for frequency here, NOT velocity) lamda = h/p (lamda = wavelength) (h is Planck's constant) using these two equations, you can calculate the frequency, wavelength, and even the energy you can also use the uncertainty in momentum (Delta p) to find the uncertainty in ...
- Wed Oct 16, 2019 10:28 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: 1B 27 [ENDORSED]
- Replies: 1
- Views: 53
Re: 1B 27 [ENDORSED]
You are correct, the uncertainty would be 10 m/s. There is an error in the solution manual. If you go to the chem14A class website and scroll down to "Solution Manual Errors 7th Edition," you will see the corrected version.
- Wed Oct 16, 2019 10:17 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Which equation to use for determining uncertainty?
- Replies: 4
- Views: 205
Re: Which equation to use for determining uncertainty?
h bar is a simplified form of Planck's constant, in which h bar is equal to h/2π. If you use the equation given in the textbook and substitute h bar as h/2π, you will see the equation that professor Lavelle gave us. This is because (h bar/2π)/2 is equal to h/4π. In regards to your question of which ...
- Wed Oct 16, 2019 9:05 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Why divide h by 4pi?
- Replies: 5
- Views: 329
Re: Why divide h by 4pi?
Through experimentation, scientists determined that the minimum uncertainty of knowing both a particles momentum and position simultaneously is this value: h/4pi.
- Tue Oct 15, 2019 9:13 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydbergs Equation
- Replies: 3
- Views: 144
Re: Rydbergs Equation
Use the equation that Lavelle gave us in the lecture E=(-hR/n^2) as the Rydberg equation. Lavelle didn't want us to use a different version of this equation that was given in the textbook, which is v=R{(1/n^2)-(1/n^2)}. He said that if we use this equation, we will just be plugging in numbers and we...
- Sun Oct 13, 2019 11:41 am
- Forum: Bond Lengths & Energies
- Topic: Bond lengths
- Replies: 15
- Views: 986
Re: Bond lengths
I believe that Dr. Lavelle mentioned this once in his lectures. A bond length between two molecules is about 10^-10m, which is equal to 1 Angstrom.
- Sat Oct 12, 2019 3:02 pm
- Forum: DeBroglie Equation
- Topic: De Broglie equation
- Replies: 5
- Views: 160
Re: De Broglie equation
Within the De Broglie equation, the mass should be in kg instead of grams in order to cancel out with the units of Planck's constant. The units for Planck's constant are J.s. The SI units of J is kg*m^2*s^-2. Thus, the units for Planck's constant are also (kg*m^2*s^-2)*s. In order to cancel out kg i...