Search found 102 matches

by SarahCoufal_1k
Sat Mar 14, 2020 5:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Submission
Replies: 8
Views: 64

Re: Final Submission

I think it's just an online test on CCLE now and you submit at the end
by SarahCoufal_1k
Sat Mar 14, 2020 5:26 pm
Forum: General Science Questions
Topic: Chemistry Final
Replies: 16
Views: 151

Re: Chemistry Final

Also, will he be posting the link to his chem 14B website?
by SarahCoufal_1k
Sat Mar 14, 2020 5:25 pm
Forum: General Science Questions
Topic: Chemistry Final
Replies: 16
Views: 151

Re: Chemistry Final

Does LaVelle's last email mean it's M/C now?
by SarahCoufal_1k
Wed Mar 11, 2020 5:57 pm
Forum: Administrative Questions and Class Announcements
Topic: final
Replies: 14
Views: 132

Re: final

Is it still in the 3 hours, or do we have more time now?
by SarahCoufal_1k
Mon Mar 09, 2020 8:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question on Midterm
Replies: 4
Views: 29

Question on Midterm

On the midterm one of the questions was:
Which combination of solutions of HCl and NaOH would produce the largest ∆T?
the answer was: 50 mL of 2 M HCl with 50 mL of 2 M NaOH
can someone explain reasoning behind this please?
by SarahCoufal_1k
Mon Mar 09, 2020 8:48 pm
Forum: General Science Questions
Topic: Test 2 Grades [ENDORSED]
Replies: 23
Views: 237

Re: Test 2 Grades [ENDORSED]

I wouldn't be surprised if we get our tests back on Wednesday as the Ta's might have to work on the final so they get the tests over with first. Do the TAs make our final or Dr. Lavelle? This is a good question. I'm not too sure but would like to know TAs make the discussion tests. Lavelle makes mi...
by SarahCoufal_1k
Mon Mar 09, 2020 12:00 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n in NFE
Replies: 19
Views: 63

Re: n in NFE

n is the number of electrons transferred in the redox equation. When you do your reduction half reaction there is a certain amount of electrons transferred and same case for the oxidation half reaction. You then have to multiply the equations to balance the electrons. when they match and cancel that...
by SarahCoufal_1k
Sun Mar 08, 2020 11:59 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: G=-nFe
Replies: 7
Views: 26

Re: G=-nFe

n is the number of electrons transferred in the redox equation. When you do your reduction half reaction there is a certain amount of electrons transferred and same case for the oxidation half reaction. You then have to multiply the equations to balance the electrons. when they match and cancel that...
by SarahCoufal_1k
Sun Mar 08, 2020 11:57 pm
Forum: Balancing Redox Reactions
Topic: Reversing the anode
Replies: 10
Views: 34

Re: Reversing the anode

Because all cell potentials are given in the reduction form and since the anode is being oxidized you switch the equation around so it represents that. Then when. calculated Ecell you can either do Ecathode-Eanode. or Ereduction+Eoxidation but you have to reverse the sign of the oxidation one
by SarahCoufal_1k
Sun Mar 08, 2020 11:55 pm
Forum: First Order Reactions
Topic: equation derivations
Replies: 5
Views: 19

Re: equation derivations

I don't think so but I would maybe ask him or a TA. Because we go over derivations a lot but we don't seem to do them on any homework problems or tests.
by SarahCoufal_1k
Thu Mar 05, 2020 5:01 pm
Forum: Van't Hoff Equation
Topic: delta G, pressure and. K
Replies: 2
Views: 39

delta G, pressure and. K

why does reaction free energy depend on pressure and the equilibrium constant?
by SarahCoufal_1k
Sun Mar 01, 2020 9:19 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetically stable?
Replies: 10
Views: 74

Re: kinetically stable?

The energy barrier (the hump) is really large so it would take a lot of energy to do the reaction so it's most likely to stay as the reactant.
by SarahCoufal_1k
Sun Mar 01, 2020 9:14 pm
Forum: General Science Questions
Topic: Review Sessions for Test 2
Replies: 4
Views: 35

Re: Review Sessions for Test 2

No. There are the peer learning sessions like step up and office hours though
by SarahCoufal_1k
Sun Mar 01, 2020 9:08 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: spontaneity
Replies: 34
Views: 222

Re: spontaneity

Gibbs free energy is the best determinant. I think it's best since it includes both entropy and enthalpy in its formula. If it's negative it is spontaneous
by SarahCoufal_1k
Sun Mar 01, 2020 9:04 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: cell diagrams
Replies: 4
Views: 28

Re: cell diagrams

Use an inert electrode. The one they used in class a lot is platinum
by SarahCoufal_1k
Sun Mar 01, 2020 9:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Comma vs Line
Replies: 5
Views: 22

Re: Cell Diagram Comma vs Line

use commas if they are in the same phase, if different phases use lines
by SarahCoufal_1k
Sun Feb 23, 2020 11:12 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox EQs
Replies: 10
Views: 75

Re: Balancing Redox EQs

First, you should balance the species being oxidized or reduced in the half reaction. Then, add water to balance oxygen. Then, add H + to balance hydrogen in acidic solutions. If the reaction is in a basic solution, you add OH - to one side of the half reaction and H 2 O to the other side to balanc...
by SarahCoufal_1k
Sun Feb 23, 2020 6:29 pm
Forum: Balancing Redox Reactions
Topic: Flow of electrons
Replies: 11
Views: 50

Re: Flow of electrons

I think it is always from anode to cathode. Oxidation is loss of electrons at the anodes so then they flow to the cathode where there is the gain of electrons which is reduction
by SarahCoufal_1k
Sun Feb 23, 2020 6:26 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: how to get n in equation
Replies: 8
Views: 47

Re: how to get n in equation

N is the number of electrons being transferred.
by SarahCoufal_1k
Sun Feb 23, 2020 6:26 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox EQs
Replies: 10
Views: 75

Balancing Redox EQs

In the examples in discussion for balancing redox equations it seems like you first add H2Os to balance Oxygens. Can you then add either OH-s or H+s depending on the EQ, or is one preferred over the other?
by SarahCoufal_1k
Sun Feb 23, 2020 6:23 pm
Forum: Balancing Redox Reactions
Topic: spontaneous
Replies: 15
Views: 93

Re: spontaneous

The reduction is spontaneous when standard reduction potential is positive
by SarahCoufal_1k
Sun Feb 23, 2020 6:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boltzmann Formula
Replies: 11
Views: 81

Re: Boltzmann Formula

W refers to the number of possible states of a molecule with equal energy. W= #of states^# atoms.
by SarahCoufal_1k
Sun Feb 16, 2020 3:22 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: spontaneity
Replies: 34
Views: 222

Re: spontaneity

Why exactly does delta G have to be negative to be considered spontaneous? If delta G is negative that means it is going from higher energy(reactants) to lower energy (products). If it is going from high to low, you need very little (if any input of energy) so it will happen spontaneously. On the o...
by SarahCoufal_1k
Sun Feb 16, 2020 3:18 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: spontaneity
Replies: 34
Views: 222

Re: spontaneity

Gibbs free energy has to be negative. B/c delta G= Delta H - T*DeltaS the others contribute to delta G
by SarahCoufal_1k
Sun Feb 16, 2020 3:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Curve
Replies: 45
Views: 334

Re: Midterm Curve

We will be getting midterms back Wednesday after lecture. The TAs will be outside
by SarahCoufal_1k
Wed Feb 12, 2020 10:48 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: entropy at equilibrium
Replies: 3
Views: 31

entropy at equilibrium

Why is entropy a maximum at equilibrium. ( looking at the equation deltaS= q/T)
by SarahCoufal_1k
Tue Feb 11, 2020 9:54 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: 4G.5
Replies: 1
Views: 18

4G.5

4G.5 is asking about positional disorder. It gives a random octahedral in the sis structure and trans structure. It says the Cis compound has 12 different orientation while the trans compound only has three. Why are there so many more orientations for the cis one?
by SarahCoufal_1k
Sun Feb 09, 2020 8:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Le Chatelier's Principle
Replies: 5
Views: 19

Re: Le Chatelier's Principle

If expanding, volume is increasing and pressure is decreasing. It will favor the side of the reaction with more moles Lavelle taught a shortcut in class that If volume is decreasing, shift towards the side of the reaction with less moles. So your question is just that in reverse. I think it is impor...
by SarahCoufal_1k
Sun Feb 09, 2020 8:51 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and Reversible
Replies: 6
Views: 29

Re: Isothermal and Reversible

What exactly does it mean for a process to be reversible? In the review session today, they said something is reversible when ΔS total=0 and since ΔS total= ΔS system + ΔS surroundings then ΔS system = -Δ S surroundings The textbook also defines a reversible process as a process that can be reverse...
by SarahCoufal_1k
Sun Feb 09, 2020 8:40 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Enthalpy versus heat
Replies: 11
Views: 76

Re: Enthalpy versus heat

In the review session today they said enthalpy is always heat, but heat is not always enthalpy. The definition of enthalpy is heat at constant pressure. So if it isn't at constant pressure, the heat can't be described as enthalpy
by SarahCoufal_1k
Sun Feb 09, 2020 8:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Finding whether exothermic or Endothermic
Replies: 4
Views: 28

Re: Finding whether exothermic or Endothermic

Another giveaway is the phases of the reactants and products. For example, if the reactant is a solid and both products are liquids, it's most likely endothermic
by SarahCoufal_1k
Sat Feb 08, 2020 3:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Pizza Rolls REVIEW Session DOWNLOAD HERE
Replies: 67
Views: 2479

Re: Pizza Rolls REVIEW Session

ELu 1J wrote:Are you only going over the answers at the Sunday review session or the Monday one as well? Thank you so much :)))


they usually go over it in the three hour session on Sunday only
by SarahCoufal_1k
Sun Feb 02, 2020 5:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Positive or negative work?
Replies: 8
Views: 40

Re: Positive or negative work?

Mathematically if delta V is negative (volume is decreased/compressed) then work is positive. Logically because the system is compressed, like with a piston, work is being done on the system so it's positive. If delta V is positive (volume is increased/expanded) then work is negative. The system is ...
by SarahCoufal_1k
Sun Feb 02, 2020 4:55 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4A.1
Replies: 12
Views: 53

Re: 4A.1

open system allows the transfer between matter and energy
closed system allows the transfer of energy but not matter
isolated system doesn't allow the transfer of energy or matter
by SarahCoufal_1k
Sun Feb 02, 2020 4:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: w = -P*delta V
Replies: 4
Views: 19

Re: w = -P*delta V

yes, the negative sign is always there. When volume is decreased/compressed, delta V is negative so work is positive overall. when volume is increased/expanded, delta V is positive and so w is negative overall. This is because when it is compressed, work goes into the system, and when it is expanded...
by SarahCoufal_1k
Sun Feb 02, 2020 4:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit
Replies: 7
Views: 82

Re: Extra Credit

There is no extra credit. Even though you missed 5, still do them. Because it sometimes just counts if you have 50 at the end of the quarter and you might still get full points.
by SarahCoufal_1k
Sun Feb 02, 2020 4:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE
Replies: 20
Views: 99

Re: ICE

You use an ICE box to find an unknown concentration. That can be either initial concentration or equilibrium concentration. When you are given Ka or Kb that will be used to find one/more than one of the equilibrium concentrations
by SarahCoufal_1k
Sun Jan 26, 2020 1:23 pm
Forum: Phase Changes & Related Calculations
Topic: steam vs liquid burn
Replies: 2
Views: 17

steam vs liquid burn

Can someone explain again why a burn from hot steam would be way worse than a burn from hot liquid?
by SarahCoufal_1k
Sun Jan 26, 2020 1:18 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: value for r
Replies: 2
Views: 16

Re: value for r

you need to look at the units of the other variables provided. Because you use r in the equation pv=nrt --> p=(n/v)*rt, you have to look to see if the concentration was given in molarity or in partial pressure which would be atm or bar. Choose the r with matching units because then they should all c...
by SarahCoufal_1k
Sun Jan 26, 2020 1:14 pm
Forum: Ideal Gases
Topic: R Constant
Replies: 26
Views: 149

Re: R Constant

It depends on the units of the other. variables provided. Choose the r with the matching units and all but the variable you are looking for should cancel out.
by SarahCoufal_1k
Sun Jan 26, 2020 1:12 pm
Forum: Phase Changes & Related Calculations
Topic: phase changes
Replies: 6
Views: 35

Re: phase changes

I believe there are 6 phase changes.
3 are endothermic: Melting (solid to liquid) vaporization (liquid to gas) sublimation (solid to gas)
3 are exothermic: freezing(liquid to solid), condensation(gas to liquid) and deposition (gas to solid)
by SarahCoufal_1k
Thu Jan 23, 2020 6:15 pm
Forum: Calculating the pH of Salt Solutions
Topic: 6D.15
Replies: 1
Views: 41

Re: 6D.15

I'm also confused by 6D.15. In part B, the solutions manual replacer AlCl3 with Al(H2O)6 ^3+. and have a Ka=1.4X10^-5. That seems like a given constant but I can't find it in any of the text.
by SarahCoufal_1k
Sun Jan 19, 2020 7:53 pm
Forum: Ideal Gases
Topic: When to use this equation
Replies: 14
Views: 93

Re: When to use this equation

it's used to convert between pressure and concentration. When you are finding K for gasses that could. be in either pressure or concentration. You manipulate the equation to get a. simpler conversion. It starts as PV=nRT. then divide by V for P=(n/V)RT. And n/v is moles/Liter which is the definition...
by SarahCoufal_1k
Sun Jan 19, 2020 7:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Temperature
Replies: 5
Views: 36

Re: Temperature

Exothermic forward reactions release heat and so when the temperature increases it favors the endothermic reverse reaction which also favors the reactants. In the same way, endothermic forward reactions favor the temp increase and forward reaction which also favors the products. This will permanentl...
by SarahCoufal_1k
Sun Jan 19, 2020 7:35 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH vs. pOH
Replies: 13
Views: 49

Re: pH vs. pOH

you find pOH by taking the -log[OH- concentration]. you find pH by taking the -log[H30+ concentration].When it is base you use the OH- concentration and when it is an acid you use the H30+ ion concentration. Also when the equation/problem only gives you one, you can find the other because pH + pOH=14
by SarahCoufal_1k
Sun Jan 19, 2020 7:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: X was ignored
Replies: 27
Views: 135

Re: X was ignored

when the K is less than 10^-3, the x subtracted. is going to make such a small difference it's acceptable and easier to just ignore it. Only ignore when it is addition or subtraction though, you should include it in multiplication or division I believe. If concentration. found is less than 5% of the...
by SarahCoufal_1k
Sun Jan 19, 2020 7:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH and pOH
Replies: 5
Views: 16

Re: pH and pOH

yes! pOH + pH = 14 so you can. just subtract 14 from whichever. concentration you have and you have the other one as well
by SarahCoufal_1k
Wed Jan 08, 2020 8:38 pm
Forum: Student Social/Study Group
Topic: Chemistry Community
Replies: 8
Views: 528

Re: Chemistry Community

5 posts a week, supposedly they check at the end of each week
by SarahCoufal_1k
Wed Jan 08, 2020 8:35 pm
Forum: Ideal Gases
Topic: Solids and Liquids
Replies: 7
Views: 47

Re: Solids and Liquids

You omit them because there is usually so much excess that the actual amount then used is insignificant in terms of molar concentration.
by SarahCoufal_1k
Wed Jan 08, 2020 8:23 pm
Forum: Student Social/Study Group
Topic: Discussion Sections
Replies: 7
Views: 72

Re: Discussion Sections

Dina 2k wrote:did the Professor mention how many discussion sections you can miss without losing points?


you turn in your homework during discussion, so I think if you don't go you would lose those 5 points of hw
by SarahCoufal_1k
Wed Jan 08, 2020 8:19 pm
Forum: Administrative Questions and Class Announcements
Topic: Sapling Learning
Replies: 9
Views: 69

Re: Sapling Learning

everything on sapling learning is voluntary and just an extra resource I believe
by SarahCoufal_1k
Wed Jan 08, 2020 8:17 pm
Forum: Ideal Gases
Topic: Gas Law
Replies: 6
Views: 42

Re: Gas Law

It allows us to convert between the partial pressure and molar concentration. the ideal gas law is PV=nRT. You then modify the equation so P=nRT/V and n/v is mol/L which is concentration. When you isolate that, p/RT=n/V which mean p/RT=concentration n. This means that partial pressure/ (gas constant...
by SarahCoufal_1k
Sat Dec 07, 2019 1:42 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: acid & bases to memorize
Replies: 3
Views: 49

Re: acid & bases to memorize

I think the best way is to memorize the strong acids and bases and if you come across one that is not on that list, it is weak. Fundametals J has a table as well that lists them. Strong Acids: HCl HI HBr H2So4 HNO3 HCLO4 HCLO3 Strong Bases: these include basically all of the group one metals + hydro...
by SarahCoufal_1k
Sat Dec 07, 2019 1:22 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Naming Coordination Compounds on Final
Replies: 2
Views: 45

Re: Naming Coordination Compounds on Final

Yes, it is probably most efficient to memorize those so you can write out compound names correctly
by SarahCoufal_1k
Thu Dec 05, 2019 5:34 pm
Forum: *Titrations & Titration Calculations
Topic: Confusion
Replies: 1
Views: 57

Re: Confusion

He was saying that 14B will start with titrations and finding out molarity when it is a weak acid/base not strong one
by SarahCoufal_1k
Thu Dec 05, 2019 5:32 pm
Forum: General Science Questions
Topic: Final
Replies: 2
Views: 67

Re: Final

cumulative final
by SarahCoufal_1k
Wed Dec 04, 2019 1:42 pm
Forum: Naming
Topic: latin names
Replies: 3
Views: 51

Re: latin names

When the overall complex in brackets is negative add -ate to the end of the transition metal name. However, in iron make it ferrate. (example of another would be nickel-nickelate)
by SarahCoufal_1k
Wed Dec 04, 2019 1:34 pm
Forum: Naming
Topic: Tips on Naming
Replies: 5
Views: 58

Re: Tips on Naming

A lot of resources on Lavelle's website!!
by SarahCoufal_1k
Sat Nov 30, 2019 11:50 pm
Forum: Student Social/Study Group
Topic: Preparing for the final
Replies: 25
Views: 219

Re: Preparing for the final

I think the TA review sessions help a lot, try to go to as may as you can even on the same subject for reinforcement etc.
by SarahCoufal_1k
Sat Nov 30, 2019 11:47 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: strong or weak base?
Replies: 13
Views: 70

Re: strong or weak base?

inorganic acids are. often much stronger than organic acids as well. Also there is a helpful table about strong acids and bases in the textbook. I believe it's in fundamentals J
by SarahCoufal_1k
Sat Nov 30, 2019 11:43 pm
Forum: Naming
Topic: Naming
Replies: 4
Views: 34

Re: Naming

I think it's because the overall compound has a negative charge. Usually when a transition metal is used it has an overall positive charge so it's odd when it's negative. Lavelle said adding -ate to transition metals sounds weird too so use that to remember it's an odd compound with an overall negat...
by SarahCoufal_1k
Sat Nov 30, 2019 10:59 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Content
Replies: 14
Views: 112

Re: Final Exam Content

Will the final have emphasis on material post midterm and discussion tests. Or is it a likely split between everything we learned?
by SarahCoufal_1k
Sat Nov 30, 2019 10:58 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2 Grades
Replies: 10
Views: 113

Re: Test 2 Grades

The grades are up on myUCLA !
by SarahCoufal_1k
Sun Nov 24, 2019 7:41 pm
Forum: Lewis Acids & Bases
Topic: Proton acceptor and proton donor?
Replies: 33
Views: 186

Re: Proton acceptor and proton donor?

Acids are proton donors. Bases are proton acceptors. Something that is acidic has a lot of protons in it, because the acids lost them (i.e donated) in the solution.
by SarahCoufal_1k
Sun Nov 24, 2019 7:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent vs linear
Replies: 56
Views: 445

Re: Bent vs linear

Bent has 1 or 2 lone pairs- either AX2E or AX2E2. They are bent because the lone pairs repel the electrons on the bonded atoms.
by SarahCoufal_1k
Sun Nov 24, 2019 7:35 pm
Forum: Trends in The Periodic Table
Topic: Pneumonic devices for trends
Replies: 4
Views: 73

Re: Pneumonic devices for trends

I do the arrow thing as well. I draw an arrow going from bottom to top on the side, and left to right. Lastly a diagonal aloo from bottom left to top right. These are all for increasing electronegativity and ionization energy.
by SarahCoufal_1k
Sun Nov 24, 2019 7:26 pm
Forum: Administrative Questions and Class Announcements
Topic: final exam
Replies: 9
Views: 105

Re: final exam

^ there is more information about the final on his syllabus
by SarahCoufal_1k
Wed Nov 20, 2019 5:26 pm
Forum: Hybridization
Topic: hybridization on the test?
Replies: 10
Views: 110

hybridization on the test?

Is Hybridization on the test? or is it only until sigma and pi bonds?
by SarahCoufal_1k
Sun Nov 17, 2019 4:27 pm
Forum: Sigma & Pi Bonds
Topic: Sigma V Pi
Replies: 5
Views: 50

Re: Sigma V Pi

Dr. Lavelle said he will go over this more in depth on Monday as well
by SarahCoufal_1k
Sun Nov 17, 2019 4:22 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: AXE formula
Replies: 32
Views: 1953

Re: AXE formula

Yes you can, and they will. usually be the same. Looking at the AXE formula, X is number of bonded pairs to central atoms and E is number of lone pairs. With this you can understand the number of electron densities but also the number of bonded atoms. So you can use both to figure out the shape and ...
by SarahCoufal_1k
Sun Nov 17, 2019 4:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR repulsion model
Replies: 8
Views: 47

Re: VSEPR repulsion model

As said above, the strength of repulsion would affect the angles, which will also affect the shape. a lone pair lone pair would have greater repulsion and so the bond angle would be larger because they can't get as close to each other
by SarahCoufal_1k
Sun Nov 17, 2019 4:15 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: AXE
Replies: 5
Views: 53

Re: AXE

I believe Dr. Lavelle said that molecules with the same AXE formula have the similar molecular shape so yes. For Example AX4 is usually tetrahedral and AX2E1 is usually trigonal pyramidal
by SarahCoufal_1k
Thu Nov 14, 2019 6:57 pm
Forum: Bond Lengths & Energies
Topic: Week 7 Homework
Replies: 15
Views: 174

Re: Week 7 Homework

I think anything not on the midterm to the beginning of the new outline is ok
by SarahCoufal_1k
Sun Nov 10, 2019 2:03 pm
Forum: Dipole Moments
Topic: Dipoles between the same elements
Replies: 3
Views: 45

Re: Dipoles between the same elements

Molecules like O2 ad Br2 and F2 etc. do not have dipoles. This is because they have the same electronegativity so each atom pulls the electrons an equal amount towards their own nucleus. Dipoles occurs when an atom pulls the electrons towards it more than another atom
by SarahCoufal_1k
Sun Nov 10, 2019 2:00 pm
Forum: Octet Exceptions
Topic: octet exceptions
Replies: 11
Views: 135

Re: octet exceptions

Basically most elements in period 3 and beyond. This is because there is now the D sub shell that can be filled. In addition Boron can be satisfied with either 8 or 6 electrons.
by SarahCoufal_1k
Sun Nov 10, 2019 1:53 pm
Forum: Dipole Moments
Topic: Boiling Point
Replies: 11
Views: 82

Re: Boiling Point

When a bond is stronger, it needs more energy to be broken. There is more energy in higher temperature. So when a bond is really strong, it needs more energy to be broken (and go to different state) i.e it has a higher boiling point/melting point. Similarly when a bond is weak, it needs little energ...
by SarahCoufal_1k
Fri Nov 08, 2019 9:54 am
Forum: Administrative Questions and Class Announcements
Topic: Homework
Replies: 2
Views: 40

Homework

Can homework this week be from the chemical bonds section? (outline 3, section 2 of the textbook)
by SarahCoufal_1k
Fri Nov 08, 2019 9:47 am
Forum: Lewis Structures
Topic: Midterm grades
Replies: 26
Views: 322

Re: Midterm grades

At least a week
by SarahCoufal_1k
Sun Nov 03, 2019 5:23 pm
Forum: Lewis Structures
Topic: More stable structures
Replies: 2
Views: 32

Re: More stable structures

I think the question on the exam may make it clear whether it wants multiple versions. For example if it is talking about resonance or if it says "make the lowest energy structure". Some lewis structure have the same formal charge when changed and others are variable. I think when you are ...
by SarahCoufal_1k
Sun Nov 03, 2019 5:20 pm
Forum: Octet Exceptions
Topic: Radical
Replies: 6
Views: 51

Re: Radical

A radical is an atom, molecule, or ion with at least one unpaired electron. This is highly reactive, because this single electron is unstable and the molecule doesn't want it.
by SarahCoufal_1k
Sun Nov 03, 2019 12:34 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configurations of ions
Replies: 4
Views: 61

Re: Electron configurations of ions

It's mainly so you won't mess up and remove it from the wrong shell. This is especially important when you get to the fourth row and start using the D block. Because you would fill up an electron from low to high energy, 4S starts out lower energy than 3d, but once 3d has an electron now it's a lowe...
by SarahCoufal_1k
Sat Nov 02, 2019 9:07 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: delta V. in. Heisenberg questions
Replies: 2
Views: 39

delta V. in. Heisenberg questions

In 1.B.27,the question says: a bowling ball of 8 .00kg is being rolled down an alley lane at 5.00 +/- 5.0 m/s. what is the minimum uncertainty in its position? For uncertainty in velocity (delta v), would it be 10 or 5? I thought it would be 10. because the range is from 0-10, however the solutions ...
by SarahCoufal_1k
Mon Oct 28, 2019 10:32 am
Forum: General Science Questions
Topic: midterm review sessions
Replies: 1
Views: 42

midterm review sessions

In light of classes being canceled, are the step-up programs/ midterm review sessions still happening today?
by SarahCoufal_1k
Wed Oct 23, 2019 11:49 pm
Forum: Properties of Light
Topic: Threshold Frequency
Replies: 5
Views: 57

Re: Threshold Frequency

I believe Threshold Frequency is the amount of energy of a photon required to displace an electron on a metal surface. The photon needs to at least match the threshold, which will result in a kinetic energy of 0.
by SarahCoufal_1k
Wed Oct 23, 2019 11:47 pm
Forum: Trends in The Periodic Table
Topic: Location of elements
Replies: 12
Views: 147

Re: Location of elements

You should probably know the groupings, because that might help determine how they react with other elements/atoms.
by SarahCoufal_1k
Wed Oct 23, 2019 11:45 pm
Forum: Trends in The Periodic Table
Topic: bond length
Replies: 9
Views: 85

Re: bond length

I think he was just talking about the different types to inform us. Also to show how the length can be shorter when attraction is greater. I think he just used the numbers to help us understand better, not have a way to calculate it.
by SarahCoufal_1k
Wed Oct 23, 2019 11:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Order of electron configuration
Replies: 6
Views: 49

Re: Order of electron configuration

After Atomic number 20 (i.e. 20 electrons) 3d has a slightly lower energy level and you want to fill them from low to high. So do 3d and then 4s
by SarahCoufal_1k
Wed Oct 23, 2019 11:38 pm
Forum: Resonance Structures
Topic: defintion
Replies: 7
Views: 82

Re: defintion

Resonance structures are different versions of lewis structures for the same molecule and there are equivalent models.
by SarahCoufal_1k
Wed Oct 23, 2019 11:30 pm
Forum: Ionic & Covalent Bonds
Topic: ground state electron configurations
Replies: 3
Views: 64

Re: ground state electron configurations

If it is in a plus 3 state, shouldn't we subtract 3 electrons instead of add?
by SarahCoufal_1k
Wed Oct 23, 2019 11:26 pm
Forum: Ionic & Covalent Bonds
Topic: What topic are we on?
Replies: 11
Views: 128

Re: What topic are we on?

Because it's a transition week you can either turn in homework on either Quantum or Chemical bonds
by SarahCoufal_1k
Wed Oct 23, 2019 11:22 pm
Forum: Ionic & Covalent Bonds
Topic: Octet Rule
Replies: 6
Views: 60

Re: Octet Rule

They don't have enough electrons to begin with to then go form an octet. It would take a lot of energy to do so I think. Hydrogen can only have two in its first shell, so it has its own version of the octet rule
by SarahCoufal_1k
Wed Oct 23, 2019 11:20 pm
Forum: Lewis Structures
Topic: lewis drawings
Replies: 8
Views: 116

Re: lewis drawings

I think a problem on a test would be to draw out the lewis structure, but it would only ask for one way. But all variations would get credit. I would ask Dr. Lavelle to be sure.
by SarahCoufal_1k
Sun Oct 13, 2019 5:35 pm
Forum: Properties of Light
Topic: 'light intensity'
Replies: 8
Views: 70

Re: 'light intensity'

I think increasing intensity of light only increases the amplitude/height of a wave but does not change wavelength or the energy emitted. So more photons would be emitted but the energy of each photon wouldn't change. To change the energy of a light wave, the frequency has to change. As we learned, ...
by SarahCoufal_1k
Sun Oct 13, 2019 5:25 pm
Forum: DeBroglie Equation
Topic: Diffraction patterns
Replies: 4
Views: 55

Re: Diffraction patterns

I'm not sure how to identify them. But constructive interference occurs when two light sourced are in phase with each other, such as peak on peak. This can result in bigger peaks. Destructive interference occurs when the light waves are not in phase with each other and as a result are smaller peaks
by SarahCoufal_1k
Sun Oct 13, 2019 5:21 pm
Forum: Significant Figures
Topic: When to apply Sig Figs
Replies: 6
Views: 89

Re: When to apply Sig Figs

during your calculations, do not round to sig figs until the final answer. I think when you are doing a problem you can write the number as 3.456.. to show you have the rest of the number saved in you calculator and are going from that
by SarahCoufal_1k
Sun Oct 13, 2019 5:16 pm
Forum: Significant Figures
Topic: How Many Sig Figs
Replies: 7
Views: 121

Re: How Many Sig Figs

On Lavelle's main page of his website there is a document that answers a bunch of questions about sig figs. One thing I noticed that was important was in addition and subtraction go by the fewest number of decimal places. But in multiplication and division just the fewest number of sig figs
by SarahCoufal_1k
Sun Oct 13, 2019 5:08 pm
Forum: SI Units, Unit Conversions
Topic: Unit conversion
Replies: 15
Views: 272

Re: Unit conversion

I think the best way to do conversions like this is to use dimensional analysis. nm to meters to angstroms. I think also be aware of what your answer looks like. For example, if you are going. from nm to angstroms thats going. from 10^-9 to 10^-10. An angstrom is smaller scale, and there are more an...
by SarahCoufal_1k
Sun Oct 06, 2019 4:50 pm
Forum: Properties of Light
Topic: unit change
Replies: 4
Views: 64

Re: unit change

It's the units of Hz. 5 Hz and 5 s^-1 and 5 cycles per second are all the same/
by SarahCoufal_1k
Sun Oct 06, 2019 4:48 pm
Forum: Limiting Reactant Calculations
Topic: Reactant vs. Reagent
Replies: 4
Views: 63

Re: Reactant vs. Reagent

For the sake of our class, I think it's reagents/reactants on the left side and products on the right side.
by SarahCoufal_1k
Sun Oct 06, 2019 4:44 pm
Forum: Limiting Reactant Calculations
Topic: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
Replies: 68
Views: 1949

Re: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]

I don't think you have to show as many steps as in discussion. However, if you mess up the final answer, but show your correct process, you might receive partial credit.

Go to advanced search