## Search found 111 matches

Mon Mar 16, 2020 2:20 am
Forum: First Order Reactions
Topic: How to solve
Replies: 3
Views: 60

### Re: How to solve

For the most part, it is just plugging in your values and solving. Sometimes you will need to do some intermediate calculations in order to obtain all the necessary values to calculate the desired answer.
Mon Mar 16, 2020 2:19 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: k
Replies: 7
Views: 138

### Re: k

Since k is the rate constant, if everything else is constant, if you increase the value of k, the reaction rate will increase.
Mon Mar 16, 2020 2:18 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: graphs and order
Replies: 2
Views: 67

### Re: graphs and order

Zero order: [A] vs time (linear)
First order: ln[A] vs time (linear)
Second order: 1/[A] vs time (linear)
Mon Mar 16, 2020 2:17 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Reverse rate Laws
Replies: 3
Views: 78

### Re: Reverse rate Laws

If you know the K for the forward reaction and if you also have the overall K, you can then determine the reverse K and therefore the rate for the reverse reaction.
Mon Mar 16, 2020 2:15 am
Forum: Zero Order Reactions
Topic: Half life
Replies: 1
Views: 45

### Re: Half life

t1/2=[A]0/2k
Sun Mar 08, 2020 9:40 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Application
Replies: 6
Views: 78

### Re: Application

I think we will usually be using:
G=-nFE
G=-RTlnQ
Sun Mar 08, 2020 9:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Vertical lines vs commas
Replies: 7
Views: 35

### Re: Vertical lines vs commas

If they are in the same state, then use commas.
Ex: Fe3+(aq),Fe2+(aq)
If they are different states, then use the vertical lines to indicate that.
Sun Mar 08, 2020 9:28 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 10
Views: 68

### Re: Platinum

If you have an ion-gas reaction or if you do not have a solid state metal/conductor on that part of the galvanic cell, then you need to include some kind of conductor like Pt(s)! Platinum is only one of them, but it's probably the most common one to use.
Sun Mar 08, 2020 9:25 pm
Forum: Balancing Redox Reactions
Topic: e- amount
Replies: 9
Views: 77

### Re: e- amount

You just need to multiply the reaction(s) to balance out the number of electrons, and then you should be able to cancel them out since they will then be equal.
Mon Mar 02, 2020 11:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7
Replies: 3
Views: 79

### Re: 6L.7

Hi there! I think for this problem, we just have to look in the Appendix for half reactions that, when we combine them, will give us the resulting equation. Hope this helps!
Sun Mar 01, 2020 9:41 pm
Forum: Balancing Redox Reactions
Topic: 6K.3d
Replies: 5
Views: 74

### Re: 6K.3d

We know that Cl2 both oxidizes and reduces, so $Cl_{2}\rightarrow 2Cl+2e^{-}$
Sun Mar 01, 2020 9:33 pm
Forum: Balancing Redox Reactions
Topic: anode/cathod reversible
Replies: 4
Views: 47

### Re: anode/cathod reversible

My guess is, same as Nicholas, that we know that electrochem reactions proceed forward to give a positive Ecell value.
Sun Mar 01, 2020 9:32 pm
Forum: Balancing Redox Reactions
Topic: basic solution
Replies: 4
Views: 48

### Re: basic solution

In a basic solution, make sure whatever is being oxidized or reduced is balanced first, then begin to balance out the oxygens and later hydrogens with water. Then balance out the inequality that the H2O creates with water on the other side and then the same number of OH- ions on the side you origina...
Sun Mar 01, 2020 9:30 pm
Forum: Balancing Redox Reactions
Topic: homework topic 6K
Replies: 4
Views: 49

### Re: homework topic 6K

This is to ensure that both sides of the equation are balanced, based on whether the solution is acidic or basic. In this case, it appears to be acidic.
Sun Mar 01, 2020 9:29 pm
Forum: Balancing Redox Reactions
Topic: 6K 1 part d
Replies: 2
Views: 60

### Re: 6K 1 part d

The 14H+ becomes 8H+ because it cancels out with the 6H+ on the other side when you are combining the two half reactions. In addition, you get the 3 as the coefficient to the molecules with carbon because you have to multiply the oxidation half reaction, which has 2 electrons by 3 in order to cancel...
Sun Feb 23, 2020 9:52 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: 3rd law of thermodynamics
Replies: 3
Views: 100

### Re: 3rd law of thermodynamics

Yes, since at 0K atoms can't move, so there is no disorder since there is no other possible state/position that the atoms could be in, which means zero entropy.
Sun Feb 23, 2020 9:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Limiting reactant and heat
Replies: 4
Views: 112

### Re: Limiting reactant and heat

Endothermic reactions require heat, so if there is not enough heat provided to the system, then the reaction cannot continue. In this sense, heat can be thought of as the "limiting reactant".
Sun Feb 23, 2020 9:41 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Standard Enthalpy of Formation
Replies: 3
Views: 116

### Re: Standard Enthalpy of Formation

If you're asked for the enthalpy change of some reaction or whatever, you'll typically be provided with values that correspond to the standard enthalpies of formation for certain components of the reaction that you can then use in your calculations to determine enthalpy change of a reaction, etc.
Sun Feb 23, 2020 9:38 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers/States
Replies: 8
Views: 96

### Re: Oxidation Numbers/States

Oxidation state is the charge of the atom with ionic chemical bonds. Oxidation number is the Roman numerals that we use to represent the oxidation state of the atom.
Sun Feb 23, 2020 9:35 pm
Forum: Balancing Redox Reactions
Topic: Polyatomic Ions
Replies: 4
Views: 38

### Re: Polyatomic Ions

I think it's good practice to know a few of them, like SO42-, or CO32-... stuff like that.
Sun Feb 16, 2020 10:03 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q=n*delta H
Replies: 5
Views: 125

### Re: q=n*delta H

Whether you use mass or the number of moles for these calculations just depends on what units the values you're given use, or if you're expected to have an answer with certain units.
Sun Feb 16, 2020 9:59 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: change in enthalpy
Replies: 2
Views: 67

### Re: change in enthalpy

Enthalpy is the heat transfer at a constant pressure... so keeping that in mind, that is why we use Cp.
Sun Feb 16, 2020 9:58 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work
Replies: 14
Views: 282

### Re: Work

Matthew Chan 1B wrote:When there is work done on a system, the work is negative. However, when the system itself does work, then work is positive.

Sorry, I meant it the other way around haha! Work is negative when the system does work. When the system has work done on it, then work is positive. Sorry about the typo!
Sun Feb 16, 2020 9:56 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Negative work
Replies: 14
Views: 241

### Re: Negative work

Work is negative when the system does work itself, which makes sense since the system is "losing" work/energy, which makes sense why it would be negative.
Sun Feb 16, 2020 9:54 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Enthalpy and Heat
Replies: 3
Views: 56

### Re: Enthalpy and Heat

Heat is the form of energy transfer from a one temperature to another, like from hot to cold. Enthalpy is the heat transfer at a constant pressure. So the heat added or lost by the system is the enthalpy change.
Sun Feb 16, 2020 9:53 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work
Replies: 14
Views: 282

### Re: Work

When there is work done on a system, the work is negative. However, when the system itself does work, then work is positive.
Tue Feb 11, 2020 2:01 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4C.3
Replies: 7
Views: 105

### Re: 4C.3

DHavo_1E wrote:Hello,

Can I ask why for constant volume we do not get an answer for the change in enthalpy? Thank you

This is because at a constant volume, qv = $\Delta U$ of the system.
Sun Feb 09, 2020 6:33 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4B.13a
Replies: 3
Views: 33

### Re: 4B.13a

Hey! The 101.325 J value is just a conversion that we should know. I think it's just good to memorize it as it's definitely important, since we measure work in joules and not L.atm!
Sun Feb 09, 2020 6:31 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Textbook question 4B.3
Replies: 3
Views: 45

### Re: Textbook question 4B.3

If this offers any reassurance, I also got 490 Joules for my answer. Either we're somehow all wrong or the solutions manual is wrong. Chem_Mod?
Sun Feb 09, 2020 6:29 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Specific Heat Capacity
Replies: 3
Views: 49

### Re: Specific Heat Capacity

Remember that \Delta H is always q, but q is not always \Delta H . We also have to keep in mind that \Delta H is only equal to q at a constant pressure. If we have constant volume, then q is equal to \Delta U . That being said, when we have a system that is being held at a constant pressure, we gene...
Sun Feb 09, 2020 6:25 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Intensive vs Extensive
Replies: 7
Views: 91

### Re: Intensive vs Extensive

I believe that extensive properties depend on how much of a sample you have, while intensive properties don't really depend on quantity of the sample or the size of the sample, etc.
Sun Feb 09, 2020 6:23 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: irreversible and reversible
Replies: 3
Views: 61

### Re: irreversible and reversible

When we have an irreversible reaction, there is a sudden change, since everything happens right away. It's like pulling the pin out of a piston and so the piston will immediately extend if there is some pressure within it after the pin is removed. When we have a reversible reaction, we have work whi...
Sun Feb 02, 2020 3:42 pm
Forum: Phase Changes & Related Calculations
Topic: phase change heat supplied
Replies: 3
Views: 59

### Re: phase change heat supplied

Transitioning from a liquid to a gas requires the breaking of bonds, which is why so much more energy is needed to make this change in comparison to the transition from solid to liquid.
Sun Feb 02, 2020 3:41 pm
Forum: Phase Changes & Related Calculations
Topic: phase change from liquid to vapor
Replies: 8
Views: 102

### Re: phase change from liquid to vapor

If you look at the heating curve of water, there is a much bigger "flat line" going from liquid to vapor than from solid to liquid, which basically tells us that there is more energy required to vaporize. With this higher amount of energy required to vaporize compared to transition from so...
Sun Feb 02, 2020 3:38 pm
Forum: Phase Changes & Related Calculations
Topic: Internal Energy, U
Replies: 6
Views: 72

### Re: Internal Energy, U

Only at constant pressure and volume! :)
Sun Feb 02, 2020 3:37 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Value of q
Replies: 11
Views: 128

### Re: Value of q

If there was a system where no energy was lost or gained/with all perfect conditions, q (of the system) = -q (of the surroundings). This is so that if there is any change in one, the other will inversely adapt/change, since if there is heat lost by the system, the surroundings will gain that heat.
Sun Feb 02, 2020 3:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 3
Views: 35

### Re: Calorimeter

I think that the negative sign indicates that the reaction is exothermic, so the system itself is losing heat, while the surroundings are gaining heat.
Mon Jan 27, 2020 12:01 am
Forum: Phase Changes & Related Calculations
Topic: Test 1
Replies: 6
Views: 63

### Re: Test 1

Wait, they'll be returned in this week's discussions?
Mon Jan 27, 2020 12:00 am
Forum: Phase Changes & Related Calculations
Topic: State Property
Replies: 6
Views: 55

### Re: State Property

A state property is a quantity that is independent of how the substance was prepared
Sun Jan 26, 2020 11:59 pm
Forum: Phase Changes & Related Calculations
Topic: Chem 14A Final Pickup
Replies: 8
Views: 84

### Re: Chem 14A Final Pickup

You will still be able to pick them up thius week
Sun Jan 26, 2020 11:59 pm
Forum: Phase Changes & Related Calculations
Topic: Hess's Law
Replies: 5
Views: 53

### Re: Hess's Law

Hess's Law states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes
Sun Jan 26, 2020 11:58 pm
Forum: Phase Changes & Related Calculations
Topic: Steam vs water
Replies: 5
Views: 57

### Steam vs water

Could someone explain the example that Lavelle went over with steam and why it has much more severe burns than liquid water?
Sun Jan 19, 2020 5:59 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: lewis structure
Replies: 11
Views: 95

### Re: lewis structure

Knowing how to draw the lewis structures won't specifically be tested (I think), but it will just help with being able to understand what happens during a reaction when doing problems with acids/bases, salts, etc. so that you can see the proton/electron transfers.
Sun Jan 19, 2020 5:54 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE Tables
Replies: 13
Views: 97

### Re: ICE Tables

It's usually because H2O is in excess, which means that we cancel it out, since there's no real change to it. I think Lavelle gave the analogy: If someone has one million dollars, and they give ten dollars to someone else, we don't say that they have \$999,990. We just say that they have about a mill...
Sun Jan 19, 2020 5:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: small Ka
Replies: 5
Views: 58

### Re: small Ka

As mentioned above, we only account for the Ka values for the weak acids, since we know that the strong acids basically dissociate 100%. Also, when x is 5% of the initial concentration, we can get rid of the x since it would be such a small negligible amount anyway.
Sat Jan 18, 2020 5:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Kc
Replies: 3
Views: 37

### K and Kc

I was just wondering if we have to know how to convert between K and K c . It's done in Example 5H.1 Suppose you are a scientist studying the reactions of SO2 and O2. If you wish to use gas molar concentrations, you must first convert the equilibrium constant K to Kc. At 400 Celsius, the equilibrium...
Wed Jan 15, 2020 2:00 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic and Exothermic Reactions Class Example
Replies: 5
Views: 58

### Endothermic and Exothermic Reactions Class Example

I was wondering if someone could help explain the example that Dr. Lavelle gave in class when discussing the reaction from N2 to 2N. I understand that N2 is more stable and therefore it is favored, but then how does that make the reaction endothermic? Thanks!
Sun Jan 12, 2020 3:07 pm
Forum: Ideal Gases
Topic: Units of Pressure
Replies: 8
Views: 73

### Re: Units of Pressure

I think that we will be given these values on a constants sheet or something like that. Just make sure that when dealing with units of pressure, pick one unit and be consistent with it throughout the problem. Be sure to not interchange them.
Sun Jan 12, 2020 3:04 pm
Forum: Ideal Gases
Topic: Bars vs atmospheres
Replies: 13
Views: 89

### Re: Bars vs atmospheres

Both are units for measuring pressure. They are both okay to use, just make sure that you stay consistent with whichever unit you choose or with whatever is given in the problem.
Sun Jan 12, 2020 3:03 pm
Forum: Ideal Gases
Topic: Test 1
Replies: 7
Views: 89

### Re: Test 1

I think if we just look at the homework problems that he has assigned and look at the difficulty level of those, that would give us a pretty good idea of what the test would look like. Also I assume whatever has been mentioned in lecture up to Test 1 would be fair game as well.
Sun Jan 12, 2020 3:02 pm
Forum: Ideal Gases
Topic: Partial Pressure
Replies: 4
Views: 31

### Re: Partial Pressure

Yeah, as Tanmay said above, I don't think that we have to know how to calculate it yet.
Sun Jan 12, 2020 2:59 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 34
Views: 687

### Re: R in PV=nRT

R just represents the gas constant, which is 8.314 J.mol-1.K-1
Sun Dec 08, 2019 4:13 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxalate
Replies: 2
Views: 120

### Re: Oxalate

Oxalate follows the polydentate "template" that Dr. Lavelle mentioned: it has atom--spacer atom--spacer atom--atom. We can see that as O--C--C--O and the O's are the atoms that bind to the metal. Therefore, it's bidentate.
Sun Dec 08, 2019 4:11 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: 2
Views: 114

### Hydrogen Bonding

In water, can SO3 (sulfur trioxide) form hydrogen bonds with the water molecules?
Sat Dec 07, 2019 1:07 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: chelating ligands [ENDORSED]
Replies: 21
Views: 6252

### Re: chelating ligands[ENDORSED]

Elizabeth Harty 3A wrote:How do you know if there are sigma bonds available for rotation?

dont sigma bonds already have the ability to rotate? so if its just a single sigma bond then it can rotate but if theres pi bonds then you cant rotate. did i answer your question?
Sat Dec 07, 2019 1:33 am
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 5059

### Re: MARSHMALLOW- FINAL REVIEW SESSION[ENDORSED]

For the Mini marshmallow worksheet, for problem 2, we are asked to write the name/formula for the coordination compound, etc. in problem 2a, the coordination compound is [Ni(NH 3 ) 2 O 2 ]Br 2 . However, in the answer key, the compound is something completely different. I just wanted to check to see...
Fri Dec 06, 2019 1:11 am
Forum: Sigma & Pi Bonds
Topic: Marshmallow 41.C
Replies: 3
Views: 161

### Re: Marshmallow 41.C

the C=C bond is the strongest because atoms that share the same/similar energies that overlap will have the strongest bonds. Thus, the homonuclear bond between C=C is the strongest out of the other options. I think this is correct... but not entirely sure
Sat Nov 30, 2019 3:41 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: chelating ligands [ENDORSED]
Replies: 21
Views: 6252

### chelating ligands[ENDORSED]

How would you determine whether a ligand can bind at multiple sites (or be chelating?) Is there a certain angle threshold? For example like in 9C.7 (I've attached an image of the isomers of diaminobenzene that the book uses). Note that B and C should be switched around to represent what the textbook...
Sat Nov 30, 2019 2:13 am
Forum: Naming
Topic: 9C3d
Replies: 4
Views: 79

### Re: 9C3d

The OH2 is just to draw attention to the fact that the oxygen is what is contributing the electrons to the central metal atom
Sat Nov 30, 2019 2:05 am
Forum: Naming
Topic: Ligand Order
Replies: 5
Views: 65

### Re: Ligand Order

Do we arrange on the basis of the element's letters or the names of element/compounds?
Sat Nov 30, 2019 2:02 am
Forum: Naming
Topic: -ido vs -o
Replies: 5
Views: 59

### Re: -ido vs -o

Are we still allowed to use -o like fluoro and chloro rather than -ido?
Sat Nov 30, 2019 2:00 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 6
Views: 94

### Re: Ligands

Yes, ligands are considered lewis bases because they are donating an electron pair.
Sun Nov 24, 2019 11:36 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: IMF [ENDORSED]
Replies: 6
Views: 501

### Re: IMF[ENDORSED]

Induced dipole is when there is a molecule that is not polar or has no dipole moment, but then it experiences a temporary dipole moment because of the dipole moment of another molecule. A dipole dipole moment is where there are two molecules that experience attraction between the partially positive...
Sun Nov 24, 2019 8:42 pm
Forum: Hybridization
Replies: 1
Views: 24

In Focus 2.61, it asks you to draw the Lewis structure for HOCO, and to identify whether or not it is a radical. Evidently, the lewis structure for HOCO results in: H-O-C=O, with the Carbon having a single electron on it, or a radical. How do we know that carbon is the atom that will have the single...
Sun Nov 24, 2019 2:40 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: IMF [ENDORSED]
Replies: 6
Views: 501

### Re: IMF[ENDORSED]

Induced dipole is when there is a molecule that is not polar or has no dipole moment, but then it experiences a temporary dipole moment because of the dipole moment of another molecule. A dipole dipole moment is where there are two molecules that experience attraction between the partially positive ...
Sun Nov 24, 2019 2:36 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Bronsted Acids/ Lewis Acids
Replies: 2
Views: 36

### Re: Bronsted Acids/ Lewis Acids

Lewis acids and bases are defined as being able to accept or donate electron pairs, while Bronsted Lowry acids and bases are defined as being able to accept or donate hydrogen ions (H+).
Sun Nov 24, 2019 1:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating complexes
Replies: 4
Views: 29

### Re: Chelating complexes

A chelating complex is a complex that contains a ligand that forms a ring of atoms that includes the central metal atom.
Sun Nov 24, 2019 1:41 pm
Forum: Biological Examples
Topic: Heme complex
Replies: 8
Views: 128

### Heme complex

Can someone explain what the Heme complex is and what significance/applications it has? Thanks.
Sun Nov 24, 2019 1:39 pm
Forum: Hybridization
Topic: Knowing when hybridization occurs
Replies: 6
Views: 65

### Re: Knowing when hybridization occurs

Orbitals hybridize whenever the resulting molecule will be lower in energy.
Sun Nov 17, 2019 10:00 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Simpler Terms
Replies: 4
Views: 397

### Re: Simpler Terms

Paramagnetic compounds have unpaired electrons while diamagnetic compounds the electrons all have paired spins.
Sun Nov 17, 2019 9:57 pm
Forum: Hybridization
Topic: Test 2
Replies: 11
Views: 137

### Test 2

If I have discussion on Tuesday, will Hybridization be on Test 2? Is it something that's going to be discussed Monday lecture?
Sun Nov 17, 2019 9:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 49

### Re: Bond Angles

With enough practice and being able to determine if something is bent or linear, etc. you can likely determine the correct bond angles because after lots of practice, it should be second-nature to remember what bonds correlate with what shapes.
Sun Nov 17, 2019 9:53 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: london forces
Replies: 5
Views: 51

### Re: london forces

Due to electrons always moving around and never staying in one set place, they sometimes create temporary dipole moments, which is why there are london forces in every bond.
Sun Nov 17, 2019 9:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: dipole moments
Replies: 11
Views: 106

### Re: dipole moments

Dipole moments cancel when there are moments facing in opposite directions, effectively canceling each other out.
Sun Nov 17, 2019 9:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: vsepr angles
Replies: 10
Views: 75

### vsepr angles

This is kind of a dumb question, but do we have to memorize the bond angles?
Wed Nov 06, 2019 10:44 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Large Anion + Small Cation
Replies: 2
Views: 61

### Re: Large Anion + Small Cation

When there is a large difference in the electronegativity between two elements, the electrons from the large electron dense regions of the large anion are pulled away from that region and (more electrons = more shielding, so electrons are held less tightly) closer to the small cation and the electro...
Wed Nov 06, 2019 10:34 pm
Forum: Dipole Moments
Topic: Hydrogen Dipoles
Replies: 3
Views: 31

### Re: Hydrogen Dipoles

We need to draw dipole moments for these bonds between the atoms, as there will inevitably be some pull of electrons one direction or the other between two atoms. Then, looking at the broader picture, we can eventually determine if the moments cancel each other out or overall point in a certain dire...
Wed Nov 06, 2019 10:27 pm
Forum: Resonance Structures
Topic: resonance importance?
Replies: 7
Views: 97

### Re: resonance importance?

Electrons don't actually stay in place like how they look in Lewis structures. They are not stationary. They are constantly moving around and thus, the resonance structures allow us to get a better picture of what the actual molecule looks like, since resonance depicts how the electrons may move aro...
Wed Nov 06, 2019 10:25 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Central atom: formal charge v electronegativity
Replies: 3
Views: 51

### Re: Central atom: formal charge v electronegativity

You should put the more electronegative element in the center, and then try and minimize formal charges of that atom and the atoms that surround it.
Wed Nov 06, 2019 10:20 pm
Forum: Dipole Moments
Topic: Dipole moments
Replies: 5
Views: 71

### Re: Dipole moments

Dipole moments arise from differences in electronegativity in a covalent bond between two atoms. The arrow of the dipole moment is generally pointed towards the element that is more electronegative. They represent the direction in which the electrons are pulled toward, given the differences in elect...
Sat Nov 02, 2019 8:21 pm
Forum: Bond Lengths & Energies
Topic: Electron Density and Bond Length
Replies: 1
Views: 43

### Electron Density and Bond Length

Can someone explain why a bigger electron density region means that there will be a longer bond?
Sat Nov 02, 2019 8:02 pm
Forum: Electronegativity
Topic: electronegativity
Replies: 3
Views: 54

### Re: electronegativity

On the periodic table that we got for test 1, we didn't get electronegativity values. However, if we're just comparing values, we have to know the trends of electronegativity across the periodic table. The trend is that electronegativity increases from left to right, and increases from bottom to top...
Sat Nov 02, 2019 7:57 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds question
Replies: 3
Views: 75

### sigma and pi bonds question

Do we have to know about sigma and pi bonds for the upcoming midterm? I don't remember anything being said in class, but I see this topic thread, so I'm not sure now. Does anyone know? Thanks.
Sat Nov 02, 2019 7:52 pm
Forum: Lewis Structures
Topic: Drawing Structures for Ionic Bonds
Replies: 2
Views: 31

### Re: Drawing Structures for Ionic Bonds

You would draw the lewis structure of each ion and draw them next to each other.
Sat Nov 02, 2019 7:51 pm
Forum: Lewis Structures
Topic: Formal Charge for Lewis Structures
Replies: 4
Views: 61

### Re: Formal Charge for Lewis Structures

My TA told me whenever drawing Lewis structures, we should always try and calculate formal charges. We should do this to make sure we're drawing the most accurate structure that we can.
Sat Oct 26, 2019 3:37 pm
Forum: Quantum Numbers and The H-Atom
Topic: ionization energy and electron affinty
Replies: 3
Views: 60

### Re: ionization energy and electron affinty

Ionization Energy: the energy required to remove an electron from a gas-phase atom

Electron Affinity: the energy released when an electron is added to a gas-phase atom
Sat Oct 26, 2019 3:31 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 4
Views: 53

I don't think that it was explicitly mentioned in the outline for the Quantum World unit, and I never heard him state it in class.

I could be wrong, though.
Sat Oct 26, 2019 3:30 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Exceptions
Replies: 2
Views: 34

### Re: Electron Configuration Exceptions

Chromium: [Ar]3d 5 4s 1 Takes the electron from the 4s subshell and adds it to the 3d subshell because 3d will be more stable with that fifth electron, since it will now be half filled. Copper: [Ar]3d 10 4s 1 Takes the electron from the 4s subshell and adds it to the 3d subshell because 3d will be m...
Sat Oct 26, 2019 3:23 pm
Forum: Trends in The Periodic Table
Topic: First vs. Second Ionization Energies
Replies: 2
Views: 34

### Re: First vs. Second Ionization Energies

The second ionization energy is higher than the first ionization energy because, in short, it takes more energy to remove an electron from a positively-charged atom (cation) than it does to remove an electron from a neutral atom. When an electron is removed, that means there's more protons than elec...
Sat Oct 26, 2019 3:20 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge and Ionization Energy
Replies: 2
Views: 30

### Re: Effective Nuclear Charge and Ionization Energy

Effective nuclear charge means the amount of force that the electrons in the valence shell experience. And so, as the effective nuclear charge increases, that means the electrons are being held on to more tightly, which means that it will require more energy to remove the electrons from the valence ...
Sat Oct 19, 2019 5:49 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Determining # of Subshells in an Orbital
Replies: 3
Views: 55

### Re: Determining # of Subshells in an Orbital

Subshells, aka the angular momentum quantum number, are represented by the letter l . We calculate l by taking our principle quantum number n , and subtracting one from it. l = n -1. Then, to calculate how many orbitals are in the subshell, we take the value of l and all numbers equal to and in betw...
Sat Oct 19, 2019 11:56 am
Forum: *Shrodinger Equation
Topic: Psi ^2
Replies: 2
Views: 32

### Re: Psi ^2

I think that it's something we just have to accept as fact. It's a pretty complicated mathematical equation, but basically it's said that the probability of obtaining any possible measurement outcome is equal to the square of the corresponding amplitude. Not sure, but hopefully this helps. Also, Tif...
Sat Oct 19, 2019 11:45 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: HW 1B.27
Replies: 2
Views: 42

### Re: HW 1B.27

There is an error in the solution manual. Check Dr. Lavelle's solution manual errors PDF on his website; he addresses that mistake.

https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf
Sat Oct 19, 2019 11:43 am
Forum: *Particle in a Box
Topic: Shape of Wavefunction
Replies: 4
Views: 644

### Re: Shape of Wavefunction

$\psi$: tells us what the height of the wave at a certain position (x,y,z) is. It basically tells us something about the wave of an electron given a certain position
$\psi ^{2}$: tells us the probability of finding an electron within a certain space.
Sat Oct 19, 2019 11:39 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell/Orbital Energies
Replies: 2
Views: 30

### Re: Shell/Orbital Energies

Higher numbered shells (like n=2 to n=1) have higher energy because of the force that it takes for the nucleus to hold onto the electron. When the electron is closer, it takes less energy to keep the electron. However, as the electrons are further out/further away from the nucleus, it takes more ene...
Thu Oct 17, 2019 11:44 pm
Forum: Photoelectric Effect
Topic: Quick Question
Replies: 3
Views: 72

### Quick Question

I was wondering if ionization energy and threshold energy are related. Are they the same? Or is there a difference? The textbook gives a definition that seems pretty similar to what threshold energy is. Thanks in advance for clarifying.
Sun Oct 13, 2019 11:33 pm
Forum: Photoelectric Effect
Topic: Threshold Energy
Replies: 4
Views: 64

### Re: Threshold Energy

Yes, different elements will hold onto their electrons with different amounts of strength. Thus, we can say that the threshold energy does indeed vary between elements.
Sun Oct 13, 2019 11:31 pm
Forum: Photoelectric Effect
Topic: Intensity vs. Length of Waves
Replies: 4
Views: 60

### Re: Intensity vs. Length of Waves

A shorter wavelength means that the energy of the radiation increases. Fluctuation in the wavelength of the radiation affects the energy. Intensity is not affected by changing the frequency/wavelength. You can think of the intensity as the amplitude of the wave. Hope this helps.
Sun Oct 13, 2019 11:26 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 3
Views: 48

### Re: Photoelectric Effect

Non-metals will not exhibit the photoelectric effect due to the fact that they do not have any 'spare' electrons in their outer shells. However, metals do contain these 'spare' electrons. These electrons are the ones that can be dislodged/removed by a photon of light that has sufficient energy to do...
Sun Oct 13, 2019 11:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy