Search found 102 matches
- Sat Mar 14, 2020 5:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Submission
- Replies: 8
- Views: 743
Re: Final Submission
I think it's just an online test on CCLE now and you submit at the end
- Sat Mar 14, 2020 5:26 pm
- Forum: General Science Questions
- Topic: Chemistry Final
- Replies: 16
- Views: 1163
Re: Chemistry Final
Also, will he be posting the link to his chem 14B website?
- Sat Mar 14, 2020 5:25 pm
- Forum: General Science Questions
- Topic: Chemistry Final
- Replies: 16
- Views: 1163
Re: Chemistry Final
Does LaVelle's last email mean it's M/C now?
- Wed Mar 11, 2020 5:57 pm
- Forum: Administrative Questions and Class Announcements
- Topic: final
- Replies: 14
- Views: 923
Re: final
Is it still in the 3 hours, or do we have more time now?
- 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: 391
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?
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?
- Mon Mar 09, 2020 8:48 pm
- Forum: General Science Questions
- Topic: Test 2 Grades [ENDORSED]
- Replies: 23
- Views: 1567
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...
- Mon Mar 09, 2020 12:00 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in NFE
- Replies: 64
- Views: 3000
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...
- Sun Mar 08, 2020 11:59 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: G=-nFe
- Replies: 7
- Views: 792
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...
- Sun Mar 08, 2020 11:57 pm
- Forum: Balancing Redox Reactions
- Topic: Reversing the anode
- Replies: 10
- Views: 661
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
- Sun Mar 08, 2020 11:55 pm
- Forum: First Order Reactions
- Topic: equation derivations
- Replies: 5
- Views: 386
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.
- Thu Mar 05, 2020 5:01 pm
- Forum: Van't Hoff Equation
- Topic: delta G, pressure and. K
- Replies: 2
- Views: 400
delta G, pressure and. K
why does reaction free energy depend on pressure and the equilibrium constant?
- Sun Mar 01, 2020 9:19 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetically stable?
- Replies: 10
- Views: 707
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.
- Sun Mar 01, 2020 9:14 pm
- Forum: General Science Questions
- Topic: Review Sessions for Test 2
- Replies: 4
- Views: 449
Re: Review Sessions for Test 2
No. There are the peer learning sessions like step up and office hours though
- Sun Mar 01, 2020 9:08 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1846
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
- Sun Mar 01, 2020 9:04 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: cell diagrams
- Replies: 4
- Views: 375
Re: cell diagrams
Use an inert electrode. The one they used in class a lot is platinum
- 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: 310
Re: Cell Diagram Comma vs Line
use commas if they are in the same phase, if different phases use lines
- Sun Feb 23, 2020 11:12 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox EQs
- Replies: 10
- Views: 661
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...
- Sun Feb 23, 2020 6:29 pm
- Forum: Balancing Redox Reactions
- Topic: Flow of electrons
- Replies: 11
- Views: 760
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
- 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: 503
Re: how to get n in equation
N is the number of electrons being transferred.
- Sun Feb 23, 2020 6:26 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox EQs
- Replies: 10
- Views: 661
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?
- Sun Feb 23, 2020 6:23 pm
- Forum: Balancing Redox Reactions
- Topic: spontaneous
- Replies: 15
- Views: 798
Re: spontaneous
The reduction is spontaneous when standard reduction potential is positive
- Sun Feb 23, 2020 6:14 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Boltzmann Formula
- Replies: 11
- Views: 869
Re: Boltzmann Formula
W refers to the number of possible states of a molecule with equal energy. W= #of states^# atoms.
- Sun Feb 16, 2020 3:22 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1846
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...
- Sun Feb 16, 2020 3:18 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1846
Re: spontaneity
Gibbs free energy has to be negative. B/c delta G= Delta H - T*DeltaS the others contribute to delta G
- Sun Feb 16, 2020 3:15 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm Curve
- Replies: 45
- Views: 2165
Re: Midterm Curve
We will be getting midterms back Wednesday after lecture. The TAs will be outside
- Wed Feb 12, 2020 10:48 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: entropy at equilibrium
- Replies: 3
- Views: 241
entropy at equilibrium
Why is entropy a maximum at equilibrium. ( looking at the equation deltaS= q/T)
- 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: 3
- Views: 226
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?
- Sun Feb 09, 2020 8:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Le Chatelier's Principle
- Replies: 5
- Views: 282
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...
- Sun Feb 09, 2020 8:51 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal and Reversible
- Replies: 6
- Views: 135
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...
- Sun Feb 09, 2020 8:40 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Enthalpy versus heat
- Replies: 11
- Views: 536
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
- Sun Feb 09, 2020 8:37 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Finding whether exothermic or Endothermic
- Replies: 4
- Views: 156
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
- Sat Feb 08, 2020 3:40 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Pizza Rolls REVIEW Session DOWNLOAD HERE
- Replies: 67
- Views: 5548
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
- Sun Feb 02, 2020 5:07 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Positive or negative work?
- Replies: 8
- Views: 267
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 ...
- Sun Feb 02, 2020 4:55 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 4A.1
- Replies: 12
- Views: 478
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
closed system allows the transfer of energy but not matter
isolated system doesn't allow the transfer of energy or matter
- Sun Feb 02, 2020 4:44 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: w = -P*delta V
- Replies: 4
- Views: 180
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...
- Sun Feb 02, 2020 4:36 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Extra Credit
- Replies: 7
- Views: 413
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.
- Sun Feb 02, 2020 4:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE
- Replies: 20
- Views: 877
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
- Sun Jan 26, 2020 1:23 pm
- Forum: Phase Changes & Related Calculations
- Topic: steam vs liquid burn
- Replies: 2
- Views: 115
steam vs liquid burn
Can someone explain again why a burn from hot steam would be way worse than a burn from hot liquid?
- Sun Jan 26, 2020 1:18 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: value for r
- Replies: 2
- Views: 68
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...
- Sun Jan 26, 2020 1:14 pm
- Forum: Ideal Gases
- Topic: R Constant
- Replies: 26
- Views: 1134
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.
- Sun Jan 26, 2020 1:12 pm
- Forum: Phase Changes & Related Calculations
- Topic: phase changes
- Replies: 6
- Views: 239
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)
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)
- Thu Jan 23, 2020 6:15 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: 6D.15
- Replies: 1
- Views: 152
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.
- Sun Jan 19, 2020 7:53 pm
- Forum: Ideal Gases
- Topic: When to use this equation
- Replies: 14
- Views: 434
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...
- Sun Jan 19, 2020 7:41 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Temperature
- Replies: 5
- Views: 186
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...
- 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: 396
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
- Sun Jan 19, 2020 7:24 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: X was ignored
- Replies: 27
- Views: 1062
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...
- 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: 221
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
- Wed Jan 08, 2020 8:38 pm
- Forum: Student Social/Study Group
- Topic: Chemistry Community
- Replies: 8
- Views: 1315
Re: Chemistry Community
5 posts a week, supposedly they check at the end of each week
- Wed Jan 08, 2020 8:35 pm
- Forum: Ideal Gases
- Topic: Solids and Liquids
- Replies: 7
- Views: 431
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.
- Wed Jan 08, 2020 8:23 pm
- Forum: Student Social/Study Group
- Topic: Discussion Sections
- Replies: 7
- Views: 399
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
- Wed Jan 08, 2020 8:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Sapling Learning
- Replies: 9
- Views: 495
Re: Sapling Learning
everything on sapling learning is voluntary and just an extra resource I believe
- Wed Jan 08, 2020 8:17 pm
- Forum: Ideal Gases
- Topic: Gas Law
- Replies: 6
- Views: 235
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...
- 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: 293
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...
- Sat Dec 07, 2019 1:22 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Naming Coordination Compounds on Final
- Replies: 2
- Views: 142
Re: Naming Coordination Compounds on Final
Yes, it is probably most efficient to memorize those so you can write out compound names correctly
- Thu Dec 05, 2019 5:34 pm
- Forum: *Titrations & Titration Calculations
- Topic: Confusion
- Replies: 1
- Views: 460
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
- Thu Dec 05, 2019 5:32 pm
- Forum: General Science Questions
- Topic: Final
- Replies: 2
- Views: 192
Re: Final
cumulative final
- Wed Dec 04, 2019 1:42 pm
- Forum: Naming
- Topic: latin names
- Replies: 3
- Views: 230
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)
- Wed Dec 04, 2019 1:34 pm
- Forum: Naming
- Topic: Tips on Naming
- Replies: 5
- Views: 394
Re: Tips on Naming
A lot of resources on Lavelle's website!!
- Sat Nov 30, 2019 11:50 pm
- Forum: Student Social/Study Group
- Topic: Preparing for the final
- Replies: 25
- Views: 1195
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.
- 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: 866
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
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...
- Sat Nov 30, 2019 10:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam Content
- Replies: 14
- Views: 766
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?
- Sat Nov 30, 2019 10:58 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 Grades
- Replies: 10
- Views: 648
Re: Test 2 Grades
The grades are up on myUCLA !
- Sun Nov 24, 2019 7:41 pm
- Forum: Lewis Acids & Bases
- Topic: Proton acceptor and proton donor?
- Replies: 33
- Views: 2074
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.
- Sun Nov 24, 2019 7:39 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent vs linear
- Replies: 56
- Views: 4088
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.
- Sun Nov 24, 2019 7:35 pm
- Forum: Trends in The Periodic Table
- Topic: Pneumonic devices for trends
- Replies: 4
- Views: 305
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.
- Sun Nov 24, 2019 7:26 pm
- Forum: Administrative Questions and Class Announcements
- Topic: final exam
- Replies: 9
- Views: 615
Re: final exam
^ there is more information about the final on his syllabus
- Wed Nov 20, 2019 5:26 pm
- Forum: Hybridization
- Topic: hybridization on the test?
- Replies: 10
- Views: 619
hybridization on the test?
Is Hybridization on the test? or is it only until sigma and pi bonds?
- Sun Nov 17, 2019 4:27 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma V Pi
- Replies: 5
- Views: 437
Re: Sigma V Pi
Dr. Lavelle said he will go over this more in depth on Monday as well
- Sun Nov 17, 2019 4:22 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: AXE formula
- Replies: 32
- Views: 12103
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 ...
- Sun Nov 17, 2019 4:18 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR repulsion model
- Replies: 8
- Views: 570
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
- Sun Nov 17, 2019 4:15 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: AXE
- Replies: 5
- Views: 336
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
- Thu Nov 14, 2019 6:57 pm
- Forum: Bond Lengths & Energies
- Topic: Week 7 Homework
- Replies: 15
- Views: 821
Re: Week 7 Homework
I think anything not on the midterm to the beginning of the new outline is ok
- Sun Nov 10, 2019 2:03 pm
- Forum: Dipole Moments
- Topic: Dipoles between the same elements
- Replies: 3
- Views: 267
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
- Sun Nov 10, 2019 2:00 pm
- Forum: Octet Exceptions
- Topic: octet exceptions
- Replies: 11
- Views: 566
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.
- Sun Nov 10, 2019 1:53 pm
- Forum: Dipole Moments
- Topic: Boiling Point
- Replies: 11
- Views: 686
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...
- Fri Nov 08, 2019 9:54 am
- Forum: Administrative Questions and Class Announcements
- Topic: Homework
- Replies: 2
- Views: 199
Homework
Can homework this week be from the chemical bonds section? (outline 3, section 2 of the textbook)
- Fri Nov 08, 2019 9:47 am
- Forum: Lewis Structures
- Topic: Midterm grades
- Replies: 26
- Views: 1370
Re: Midterm grades
At least a week
- Sun Nov 03, 2019 5:23 pm
- Forum: Lewis Structures
- Topic: More stable structures
- Replies: 2
- Views: 180
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 ...
- Sun Nov 03, 2019 5:20 pm
- Forum: Octet Exceptions
- Topic: Radical
- Replies: 6
- Views: 281
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.
- Sun Nov 03, 2019 12:34 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configurations of ions
- Replies: 4
- Views: 356
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...
- Sat Nov 02, 2019 9:07 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: delta V. in. Heisenberg questions
- Replies: 6
- Views: 536
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 ...
- Mon Oct 28, 2019 10:32 am
- Forum: General Science Questions
- Topic: midterm review sessions
- Replies: 1
- Views: 130
midterm review sessions
In light of classes being canceled, are the step-up programs/ midterm review sessions still happening today?
- Wed Oct 23, 2019 11:49 pm
- Forum: Properties of Light
- Topic: Threshold Frequency
- Replies: 5
- Views: 279
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.
- Wed Oct 23, 2019 11:47 pm
- Forum: Trends in The Periodic Table
- Topic: Location of elements
- Replies: 12
- Views: 695
Re: Location of elements
You should probably know the groupings, because that might help determine how they react with other elements/atoms.
- Wed Oct 23, 2019 11:45 pm
- Forum: Trends in The Periodic Table
- Topic: bond length
- Replies: 9
- Views: 408
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.
- Wed Oct 23, 2019 11:42 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Order of electron configuration
- Replies: 6
- Views: 235
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
- Wed Oct 23, 2019 11:38 pm
- Forum: Resonance Structures
- Topic: defintion
- Replies: 7
- Views: 432
Re: defintion
Resonance structures are different versions of lewis structures for the same molecule and there are equivalent models.
- Wed Oct 23, 2019 11:30 pm
- Forum: Ionic & Covalent Bonds
- Topic: ground state electron configurations
- Replies: 3
- Views: 223
Re: ground state electron configurations
If it is in a plus 3 state, shouldn't we subtract 3 electrons instead of add?
- Wed Oct 23, 2019 11:26 pm
- Forum: Ionic & Covalent Bonds
- Topic: What topic are we on?
- Replies: 11
- Views: 544
Re: What topic are we on?
Because it's a transition week you can either turn in homework on either Quantum or Chemical bonds
- Wed Oct 23, 2019 11:22 pm
- Forum: Ionic & Covalent Bonds
- Topic: Octet Rule
- Replies: 6
- Views: 198
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
- Wed Oct 23, 2019 11:20 pm
- Forum: Lewis Structures
- Topic: lewis drawings
- Replies: 8
- Views: 447
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.
- Sun Oct 13, 2019 5:35 pm
- Forum: Properties of Light
- Topic: 'light intensity'
- Replies: 8
- Views: 238
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, ...
- Sun Oct 13, 2019 5:25 pm
- Forum: DeBroglie Equation
- Topic: Diffraction patterns
- Replies: 4
- Views: 192
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
- Sun Oct 13, 2019 5:21 pm
- Forum: Significant Figures
- Topic: When to apply Sig Figs
- Replies: 6
- Views: 346
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
- Sun Oct 13, 2019 5:16 pm
- Forum: Significant Figures
- Topic: How Many Sig Figs
- Replies: 7
- Views: 410
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
- Sun Oct 13, 2019 5:08 pm
- Forum: SI Units, Unit Conversions
- Topic: Unit conversion
- Replies: 15
- Views: 1521
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...
- Sun Oct 06, 2019 4:50 pm
- Forum: Properties of Light
- Topic: unit change
- Replies: 4
- Views: 227
Re: unit change
It's the units of Hz. 5 Hz and 5 s^-1 and 5 cycles per second are all the same/
- Sun Oct 06, 2019 4:48 pm
- Forum: Limiting Reactant Calculations
- Topic: Reactant vs. Reagent
- Replies: 4
- Views: 292
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.
- Sun Oct 06, 2019 4:44 pm
- Forum: Limiting Reactant Calculations
- Topic: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
- Replies: 68
- Views: 6657
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.