## Search found 108 matches

Sat Mar 15, 2014 10:59 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Control vs Favorable
Replies: 6
Views: 1158

### Re: Control vs Favorable

So basically a high activation energy means kinetic control, and the opposite means thermodynamic control? What is the basis behind this naming?
Mon Mar 10, 2014 3:17 pm
Forum: *Alkanes
Topic: -ylium
Replies: 2
Views: 605

### Re: -ylium

When an hydrogen is removed to make the substance a cation, you can use the ending '-ylium,' I believe.
Fri Mar 07, 2014 4:05 pm
Forum: *Chem3D
Topic: 7. CCH Angle for Cyclobutane
Replies: 4
Views: 1114

### Re: 7. CCH Angle for Cyclobutane

Thanks. I just went along and wrote both and then put the average in parentheses.
Fri Mar 07, 2014 2:29 pm
Forum: *Chem3D
Topic: 5. MM2 Energy in kcal/mol
Replies: 1
Views: 893

### 5. MM2 Energy in kcal/mol

When I minimize the structure for the first time I get 2.1746 kcal/mol, but if I continue to minimize, it goes to 2.1733. Should I use 2.173, 2.174, 2.175 for this answer?
Fri Mar 07, 2014 11:29 am
Forum: *Chem3D
Topic: 7. CCH Angle for Cyclobutane
Replies: 4
Views: 1114

### 7. CCH Angle for Cyclobutane

When I used Chem3D to calculate the CCH angle for cyclobutane, there were several values between 112 degrees and 115 degrees but more of them were toward the 115 degree side. What value should I write?
Fri Mar 07, 2014 11:22 am
Forum: *Chem3D
Topic: 7. Cyclobutane calculated geometries
Replies: 1
Views: 870

### 7. Cyclobutane calculated geometries

Hello, on the worksheet it says that we should round to the nearest degree for the Calculated geometries and bond angles section for number 7.

However, the beginning tells us to round to the nearest 3 decimal places. What should we do?
Tue Feb 11, 2014 12:31 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: Winter 2013 Q5B
Replies: 1
Views: 448

### Re: Winter 2013 Q5B

Things with more molar mass will have a higher entropy. Each molecule can be in 5 states, but CF4 is larger than say CHF3.
Tue Feb 11, 2014 12:30 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Winter 2013 Midterm Q7-F constant
Replies: 1
Views: 400

### Re: Winter 2013 Midterm Q7-F constant

It should read 96485.3 C/mol. It's a typo.
Tue Feb 11, 2014 12:29 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Winter 2013 Midterm Q8B
Replies: 1
Views: 389

### Re: Winter 2013 Midterm Q8B

The equation they use is the same equation as the ln equation but with the constants converted to match a log value. Either one can be used to find the right answer.
Sun Feb 09, 2014 8:04 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 2012 Midterm Question 3A
Replies: 5
Views: 1224

### Re: 2012 Midterm Question 3A

W is degeneracy, the number of positions a given molecule can be in, usually given by the number of possible positions of a molecule to the power, such as 2^3 for 3HBr(g). Kb is the Boltzmann Constant which can be found in the formula sheet.
Sun Feb 09, 2014 8:01 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Potential and Oxidizing Agents
Replies: 1
Views: 465

### Re: Cell Potential and Oxidizing Agents

A higher cell potential = a higher tendency to be reduced. Something that is more easily reduced is a stronger oxidating agent.
Mon Feb 03, 2014 8:44 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: electrode
Replies: 1
Views: 331

### Re: electrode

I think the most popular is platinum...I haven't seen carbon, but the electrode should first be whatever metal is in the equation and if none exist, then you can use platinum.
Mon Feb 03, 2014 8:43 am
Forum: Significant Figures
Topic: sig figs with natural logarithms
Replies: 1
Views: 564

### Re: sig figs with natural logarithms

Technically log(x) and ln(x) are the same thing with a different base, so I would assume so.
Mon Feb 03, 2014 8:42 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Enaught given half-reaction Enaughts
Replies: 1
Views: 453

### Re: Calculating Enaught given half-reaction Enaughts

Remember that the Enaught is always the reduction voltage, so when you subtract the anode from the cathode, you're not rearranging the equations to make sure that the electrons balance on both sides. This may a be a little bit confusing so I prefer just writing the half equations and adding/subtract...
Mon Feb 03, 2014 8:41 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram
Replies: 4
Views: 619

### Re: cell diagram

The anode should be on the left and the cathode on the right.
Sat Jan 25, 2014 2:57 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: calculating change in molar entropy
Replies: 1
Views: 829

### Re: calculating change in molar entropy

You can set your own values for initial volume and final volume.

Vi = 1 L
Vf = 3 L

Then use the equation delta S = R ln(Vf/Vi)
Sat Jan 25, 2014 2:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 7.75 reactions
Replies: 2
Views: 440

### Re: 7.75 reactions

Benzene should be pretty easy to remember, since it is a model molecule for learning about resonance. I'm not too sure about methanol though.

I think that the table given says the names of certain molecules, so you will probably be fine without having memorized every possible organic molecule.
Sat Jan 25, 2014 2:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 7.45
Replies: 4
Views: 723

### Re: 7.45

I think that is just unnecessary information. You can use just the value of delta H = -5471 and multiply it with the rest of the equation and it will still yield the same result.
Thu Jan 23, 2014 12:31 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 7.53
Replies: 2
Views: 525

### Re: 7.53

Thank you. I think the answer book may have just put the negative inside the parenthesis for that one part instead of outside then.
Tue Jan 21, 2014 12:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 7.55 Answer
Replies: 1
Views: 373

### 7.55 Answer

For 7.55, the answer says 23.9x10^3 kJ/L. Even though I got this answer, I'm just wondering why the answer book didn't use standard scientific notation for this answer.

Thanks in advance!
Tue Jan 21, 2014 11:47 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 7.53
Replies: 2
Views: 525

### 7.53

Just a quick question. For the water's specific heat capacity, when do you know when to use -4.184 as opposed to 4.184? (Positive or negative)

Thanks!
Sun Dec 08, 2013 12:01 am
Forum: Polyprotic Acids & Bases
Topic: Overall Reaction for Polyprotic Species
Replies: 2
Views: 635

### Re: Overall Reaction for Polyprotic Species

You cannot use the overall equation because the ability of H2CO3 to lose one electron and then the other differs, and that is shown by the differing Ka values.
Sun Dec 08, 2013 12:00 am
Forum: Balancing Chemical Reactions
Topic: Fall 2009 Q 1 A
Replies: 2
Views: 611

### Re: Fall 2009 Q 1 A

Whenever something is aqueous, water is implied.
Sat Dec 07, 2013 11:58 pm
Forum: Empirical & Molecular Formulas
Topic: Fall 2009 Q 1 C
Replies: 2
Views: 582

### Re: Fall 2009 Q 1 C

You must find out how many grams are produced of C, H, and Cl to find the mass of O in the original sample.

Then you calculate the # of moles of C, H, Cl, and O to find the empirical formula for the compound, and multiply by the appropriate amount to match the molecular mass.
Sat Dec 07, 2013 11:56 pm
Forum: Empirical & Molecular Formulas
Topic: Fall 2010 Final 1 B
Replies: 1
Views: 437

### Re: Fall 2010 Final 1 B

You have to find out the molecular formula (real formula as it exists) of the substance, which can only be found by knowing the empirical formula and multiplying by the appropriate amount to reach a molar mass that they give you.
Fri Dec 06, 2013 11:47 am
Forum: *Titrations & Titration Calculations
Topic: rounding issue
Replies: 3
Views: 378

### Re: rounding issue

I think this might be because 1.8x10^(-5) is an approximation in itself.
Fri Dec 06, 2013 11:44 am
Forum: Bond Lengths & Energies
Topic: Bond Length and Resonance Structures
Replies: 3
Views: 6976

### Re: Bond Length and Resonance Structures

In terms of bond length, the bonds will be the average of all the bonds in the resonance structures. For example, in nitrite (NO2-), the resonance structures are... [::O=N-O:::] <-> [:::O-N=O::] with a lone pair on the nitrogen. However, this does not mean that there exists two forms of nitrite, wit...
Thu Dec 05, 2013 11:03 am
Forum: Polyprotic Acids & Bases
Topic: Fall 2008 Final Question 6D
Replies: 7
Views: 915

### Re: Fall 2008 Final Question 6D

Also, Ka3 becomes really small because the molecule itself becomes more negative as protons are removed, so it holds on to its remaining protons strongly.
Thu Dec 05, 2013 11:02 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Solution Manual Error?
Replies: 2
Views: 507

### Re: Solution Manual Error?

I got Kb=4.8x10^-4 as well. Should just be a typo.
Thu Dec 05, 2013 10:13 am
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Blood
Replies: 1
Views: 347

### Re: Blood

Our blood contains carbonic acid H2CO3, which has the reactions... H+ + HCO3- <-> H2CO3 <-> H2O + CO2 As CO2 is released by our body through breathing, Le Chatelier's principle will make sure that more CO2 is produced, thus lowering the amount of H+ in our system. This is why you must breathe harder...
Thu Dec 05, 2013 12:12 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Fall 2011 4e-Bond length
Replies: 2
Views: 337

### Re: Fall 2011 4e-Bond length

I think this is just a typo. It should be F2^(2-) > F2^(-) > F2 > F2^(+) with F2^(2-) demonstrating the longest bond.
Thu Dec 05, 2013 12:08 am
Forum: Polyprotic Acids & Bases
Topic: Fall 2008 Final Question 6D
Replies: 7
Views: 915

### Re: Fall 2008 Final Question 6D

What part are you confused about? This just says the question.

Ka2 means the second equilibrium constant for the reaction after one H+ has been removed. Hopefully this sets you on the right track!
Thu Dec 05, 2013 12:06 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Fall Final 2008 Question 6C
Replies: 1
Views: 368

### Re: Fall Final 2008 Question 6C

[HA] would only equal [H3O+] if all of HA dissociates in the reaction HA+H2O->H3O+ + A-. However, HA is a weak acid, so this is not the case.
Wed Dec 04, 2013 11:22 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 2007 Fall Final #5/6 A
Replies: 3
Views: 431

### Re: 2007 Fall Final #5/6 A

Would checking to see if our estimation is valid just replugging the numbers back in to find the K?
Wed Dec 04, 2013 8:44 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 2007 Fall Final #5/6 A
Replies: 3
Views: 431

### 2007 Fall Final #5/6 A

On this part of the question, the Kb is only 3.6 x 10^-4, yet the answer key approximates the 0.25M - x as 0.25M. Shouldn't this only be done when the K value is <10^-5?

Thanks.
Tue Dec 03, 2013 11:03 pm
Forum: Bronsted Acids & Bases
Topic: H2O + SO2 --> H2SO3
Replies: 10
Views: 12136

### Re: H2O + SO2 --> H2SO3

Chem_Mod, thanks for letting me know!
Tue Dec 03, 2013 10:47 pm
Forum: General Science Questions
Topic: Random question about the word "Base"
Replies: 3
Views: 1234

### Re: Random question about the word "Base"

Possibly :D But I think the fact that the world 'basin' and 'base' are so similar might be just a coincidence. Though it is a good mnemonic device.
Tue Dec 03, 2013 10:46 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 11.73
Replies: 1
Views: 239

### Re: 11.73

It doesn't work for b-d because those don't fully dissociate (they're not all strong acids). You have to use the PKa to find the concentration of H3O+ and then use that to calculate the pH.
Mon Dec 02, 2013 10:19 pm
Forum: Bronsted Acids & Bases
Topic: H2O + SO2 --> H2SO3
Replies: 10
Views: 12136

### Re: H2O + SO2 --> H2SO3

Question 2: When do products dissociate more? Do they only dissociate more if the products are strong acids/bases (i.e. sometimes conjugates of weak acids/bases) or if the products are aqueous salts? When you have a reaction that produces a strong acid/base, those will definitely dissociate. Otherw...
Mon Dec 02, 2013 10:14 pm
Forum: Bronsted Acids & Bases
Topic: H2O + SO2 --> H2SO3
Replies: 10
Views: 12136

### Re: H2O + SO2 --> H2SO3

Question 1: I know that the SO2 is the lewis acid and the H2O is the lewis base; however, is SO2 also a bronsted acid?? Does it make a difference if it is aqueous or not because if it is aqueous, it will dissociate further into SO3^2- + 2 H3O+ To dissociate means it is aqueous. In 2H2O + H2SO3 --> ...
Mon Dec 02, 2013 10:09 pm
Forum: General Science Questions
Topic: Random question about the word "Base"
Replies: 3
Views: 1234

### Re: Random question about the word "Base"

I did a quick search about the etymology of the word base and here is what I found! http://h2g2.com/dna/h2g2/alabaster/A708257"onclick="window.open(this.href);return false; Bases were identified and categorised as the substances which are neutralising acids. For that reason, the progress in the char...
Mon Dec 02, 2013 6:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 2011 Final Question 3D
Replies: 2
Views: 360

### Re: 2011 Final Question 3D

You must know that diethylenetriamine is a tridentate. There are two of them, which makes 6 areas of electron density.

6 areas of electron density = octahedral.
Mon Dec 02, 2013 6:19 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number of Cation
Replies: 2
Views: 512

### Re: Oxidation Number of Cation

Do you mean the oxidation number for the metal cation within the coordination complex? This is determined by knowing the charge of the entire coordination complex as well as the charge of each individual polyatomic ion that makes up the coordination compound. For example, if you were given Diamminet...
Mon Dec 02, 2013 6:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between Q and K
Replies: 2
Views: 436

### Re: Difference between Q and K

What's the difference between Q and K if they are calculated the same way? When do you know which one to use? K is the equilibrium constant which will indicate the direction of the reaction at equilibrium only. Q, however, is a constant that indicates the direction of a reaction at any given concen...
Mon Dec 02, 2013 5:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Which x to use when calculated final Partial Pressure
Replies: 2
Views: 380

### Re: Which x to use when calculated final Partial Pressure

Usually there will be a positive x that is too large to subtract from one of the partial pressures, so you choose the other one.
Mon Dec 02, 2013 12:06 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and its relationship with how acidic something is
Replies: 3
Views: 33602

### Re: pKa and its relationship with how acidic something is

Generally. The pKa essentially tells you how much of the acid will actually dissociate. If the pKa is low, then more of the acid will dissociate, representative of a stronger acid.

At the halfway equivalence point, pH = pKa.
Tue Nov 19, 2013 10:25 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: module 59
Replies: 2
Views: 365

### Re: module 59

What part are you confused about?
Tue Nov 19, 2013 10:20 am
Forum: Naming
Topic: Do we only need to know the names in the chart?
Replies: 2
Views: 420

### Re: Do we only need to know the names in the chart?

I would start with Lavelle's chart and then read other things for supplemental information. For the atoms that are not halides or oxygen, you just have to imagine them with an -ide ending, which you would replace with -o. For example, Nitrogen -> ion form: Nitr ide -> coordination compound form: Nit...
Tue Nov 19, 2013 10:16 am
Forum: Naming
Topic: Is Carbonate bicarbonato or bis(carbonato) [ENDORSED]
Replies: 4
Views: 801

### Re: Is Carbonate bicarbonato or bis(carbonato)[ENDORSED]

When are there 2 carbonates, you say -dicarbonato-.

You only use bis- when there is already a di- or tri- in the molecule itself, such as ethylenediamine. To denote two of those, you would say bisethylenediamine to avoid confusion.
Tue Nov 19, 2013 10:14 am
Forum: Naming
Topic: What latin names should we know?
Replies: 1
Views: 409

### Re: What latin names should we know?

I would just start with knowing the ones that are on the homework problems about coordination compounds, as those are most likely to be on the quiz.
Mon Nov 18, 2013 6:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solving ICE Table Expressions
Replies: 2
Views: 583

### Re: Solving ICE Table Expressions

You would use the quadratic formula but instead of simple integers, you'll have numbers like 1.1x10^-3, etc to put in for a, b, and c.

However, Lavelle said that if K is something to the 10^-5 or smaller, then the x's can be justifiably be eliminated from the problem for simplicity.
Thu Nov 14, 2013 10:36 am
Forum: Naming
Topic: -ate ending
Replies: 2
Views: 490

### Re: -ate ending

It seems that the metals whose names are not derived from Latin do not change, such as cobalt and nickel.
Thu Nov 14, 2013 10:35 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Distinguishing monodentates vs bidentates vs tridentates etc
Replies: 2
Views: 495

### Re: Distinguishing monodentates vs bidentates vs tridentates

It depends on how many times they bond to the central metal atom. A monodentate only bonds once, etc.

I'm pretty sure tetradentates and pentadentates exist, even if they are not so common. I don't think anything over 6 bonds can exist, though.
Thu Nov 14, 2013 10:32 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination number 4, square planar or tetrahedral?
Replies: 1
Views: 493

### Re: Coordination number 4, square planar or tetrahedral?

Usually, square planar complexes are with d8 configured transition metals, with a couple of exceptions. Otherwise, it's mostly tetrahedral.
Thu Nov 14, 2013 10:29 am
Forum: Naming
Topic: Problem from textbook ch.16, 16.29 d
Replies: 3
Views: 632

### Re: Problem from textbook ch.16, 16.29 d

I'm assuming that the bis-, tris-, etc prefixes have precedence over the others.
Thu Nov 14, 2013 10:28 am
Forum: Naming
Topic: Transition metals and alphabetical order when naming.
Replies: 2
Views: 475

### Re: Transition metals and alphabetical order when naming.

Yeah, that appears to be the case.
Thu Nov 14, 2013 10:28 am
Forum: Naming
Topic: Water as H2O or OH2?
Replies: 2
Views: 23744

### Re: Water as H2O or OH2?

It depends. You can write H2O for simplicity, but sometimes it is better to write OH2 to indicate that the oxygen is the one binding to the metal of the ligand, rather than hydrogen.
Thu Nov 14, 2013 10:27 am
Forum: Naming
Topic: Changing endings of molecules
Replies: 1
Views: 372

### Re: Changing endings of molecules

If the overall ligand charge is negative, the metal in the ligand will probably be positive so it will change to metal-ate, which some exceptions such as cobalt and nickel that just stay the way they are.

For your chloride question, if it is a Cl- inside the ligand, it will definitely be chloro-.
Thu Nov 14, 2013 10:25 am
Forum: Naming
Topic: Naming Cl2 inside ligand vs Cl2 outside of ligand
Replies: 1
Views: 643

### Re: Naming Cl2 inside ligand vs Cl2 outside of ligand

When it is outside the ligand it forms a bond ionic in character. When naming these bonds, you don't put the prefixes for number, such as in Magnesium Chloride, MgCl 2 . However, you would mention the number if the bond were more covalent in nature, such as Oxygen Dichloride, OCl 2 . Hope this helped!
Sat Nov 09, 2013 11:33 pm
Forum: Naming
Topic: Latin Names
Replies: 6
Views: 973

### Re: Latin Names

There's a list in the course reader; I would definitely take a look at those for sure. As for the others, I'm not sure if knowing them is required but they would be useful anyway, so why not?
Wed Nov 06, 2013 1:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: Number of orbitals
Replies: 3
Views: 688

### Re: Number of orbitals

Yes, but keep in mind that if they ask for specific elements, not all of these orbitals may be filled.
Wed Nov 06, 2013 11:21 am
Forum: Lewis Structures
Topic: accounting for charges on lewis structures
Replies: 1
Views: 425

### Re: accounting for charges on lewis structures

A bracket indicates that the charge is present somewhere in the molecule. In the molecule you mentioned, the negative charge is most likely on that oxygen which has a negative formal charge, so they put it there. But, you can still draw brackets around the whole thing and mark it as -1. Edit: Simpli...
Wed Nov 06, 2013 11:19 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Quick Question about Li (subscript 2)
Replies: 1
Views: 414

### Re: Quick Question about Li (subscript 2)

I think it's arbitrary, but just to demonstrate that there are many possible orbitals above the structure that are unfilled. (While lithium can have a p orbital, hydrogen cannot.) However, electrons do not fill already existing orbitals, they form the orbitals when they are at that energy state.
Wed Nov 06, 2013 11:16 am
Forum: Hybridization
Topic: Bond Composition
Replies: 1
Views: 349

### Re: Bond Composition

How would you write the bond composition for triple bond? The second pi bond would use another one of the p orbitals at a different axis. You may want to specify that they are different axes using pi(O2px) and pi(O2py) for instance. Also, in the hybridization of lone pairs, do you list the principa...
Wed Nov 06, 2013 9:50 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Products and Reactants
Replies: 1
Views: 286

### Re: Products and Reactants

It is a combustion reaction so carbon dioxide and water must be released. The only thing left is nitrogen, which comes diatomically, so N2 would be the third product.
Wed Nov 06, 2013 9:47 am
Forum: Quantum Numbers and The H-Atom
Topic: Number of orbitals
Replies: 3
Views: 688

### Re: Number of orbitals

Yes essentially. The number of different mls represent the number of orbitals.
Wed Nov 06, 2013 9:44 am
Forum: General Science Questions
Topic: J/mol
Replies: 3
Views: 940

### Re: J/mol

It depends what you want to do. For example, if you need to find the Joules per photon, you would use Avogadro's number in stoichiometry to find the joules per photon.
Wed Nov 06, 2013 9:36 am
Forum: Properties of Light
Topic: Fall 2010, Q5A
Replies: 2
Views: 585

### Re: Fall 2010, Q5A

I think it's just a precaution to let people know it's at about room temperature and not under any abnormal conditions, so it is irrelevant to what we are finding here.
Wed Nov 06, 2013 9:32 am
Forum: Hybridization
Topic: Fall 201, Q6A
Replies: 1
Views: 407

### Re: Fall 201, Q6A

They're bonded to hydrogen and the atoms next to them. Even if you didn't know that, you would assume there are lone pairs which make up a sp3 hybridization.
Tue Nov 05, 2013 10:13 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: When drawing the molecular orbital for HF
Replies: 1
Views: 359

### Re: When drawing the molecular orbital for HF

I'm not sure about the reasoning, but here is a link that I found that shows an HF molecular orbital.
http://www.science.uwaterloo.ca/~cchieh ... hetro.html
Mon Nov 04, 2013 11:56 pm
Forum: Hybridization
Topic: Do we need to know how to do the hybridization of lone pairs
Replies: 2
Views: 537

### Re: Do we need to know how to do the hybridization of lone p

I think we do. The hybridization of the lone pairs is just the hybridization of the atom. For example, that oxygen has a double bond and 2 lone pairs. Therefore the lone pairs are Osp2, since they are not bonded to any other atom.
Mon Nov 04, 2013 10:00 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Spacing in MO Diagrams
Replies: 3
Views: 613

### Re: Spacing in MO Diagrams

I don't think we'll be asked to draw in the lines, but we may possibly have to understand why certain energy levels for electrons are lower.

I think we'll be fine as long as we can demonstrate we know the concept.
Mon Nov 04, 2013 9:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Fe2+
Replies: 4
Views: 2138

### Re: Electron Configuration of Fe2+

I don't think so. Transition metals tend to lose their s-shell electrons and retain their d's.
Mon Nov 04, 2013 5:25 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Writing Valence Electron Configurations
Replies: 1
Views: 340

### Re: Writing Valence Electron Configurations

I believe Lavelle said that either is acceptable. In the course reader, it's in the shortened form.
Sun Nov 03, 2013 4:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Specificity of Molecular Angles
Replies: 1
Views: 308

### Specificity of Molecular Angles

One of the things I encountered on the homework was NH3 which is trigonal pyramidal with a tetrahedral arrangement. I know the actual angle is about 107 degrees, but for these kind of questions, would <109.5 degrees be acceptable?
Sun Nov 03, 2013 3:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: 5C on fall 2008 midterm
Replies: 2
Views: 479

### Re: 5C on fall 2008 midterm

Are you asking why it can't be 0? I think it's because it's filled in the order of -1, 0, then 1, which means that 0 can never be filled last. If you are just asking about why those numbers would be chosen, it is because the p orbital has 3 orientations, so the numbers -1, 0, and 1 correspond to the...
Sun Nov 03, 2013 2:56 pm
Forum: Trends in The Periodic Table
Topic: Smallest Value?
Replies: 2
Views: 570

### Re: Smallest Value?

I was a little confused by this as well. Chem_Mod, please help.
Sun Nov 03, 2013 2:55 pm
Forum: Properties of Light
Topic: Fall 2008 Q2B
Replies: 1
Views: 445

### Re: Fall 2008 Q2B

The wavelength (lambda) equals Planck's constant divided by momentum. Momentum is denoted p and can become mass times velocity. So you have lambda = h/p lambda = h/mv Rearrange by multiply v to the top and dividing lambda to the bottom v = h/m*lambda Then you can enter your numbers to find the veloc...
Sun Nov 03, 2013 2:52 pm
Forum: Properties of Light
Topic: Fall 2009 Q4
Replies: 2
Views: 503

### Re: Fall 2009 Q4

I think it's just showing that the energy you need to eject an electron is the same as the ionization energy (as it should be because that is the definition!) Basically, the "energy to eject an electron," "ionization energy," and "work function" more or less refer to E(...
Sun Nov 03, 2013 2:41 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Equations Shortcut
Replies: 2
Views: 3777

### Re: Balancing Equations Shortcut

There are several techniques you can use to balance equations. First is the cross-over method that generally works when you have different amounts of the same element on both sides in molecules. (e.g. NH3 and H2). The 3 from NH3 will become the multiple of H2 and vice versa for 2NH3 and 3H2. These c...
Fri Nov 01, 2013 5:08 pm
Forum: Hybridization
Topic: Different Hybrid Orbital Bonds
Replies: 3
Views: 565

### Re: Different Hybrid Orbital Bonds

I'm not sure what you mean here. The hybridization of an atom, more or less, describes the bonds that it is making. For example, the Carbon in Methane (CH4) is sp3 hybridized because of its four bonds.
Fri Nov 01, 2013 5:03 pm
Forum: Administrative Questions and Class Announcements
Topic: Happy Halloween
Replies: 6
Views: 1313

### Re: Happy Halloween

That's not a yellow rabbit; that's Pikachu!

http://images1.wikia.nocookie.net/__cb2 ... ikachu.png
Mon Oct 28, 2013 3:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula
Replies: 3
Views: 634

### Re: VSEPR Formula

What do you mean by the VSEPR formula? If you're talking about hybridization, each unpaired electron counts as one area of electron density, I believe.
Mon Oct 28, 2013 3:22 pm
Forum: Dipole Moments
Topic: Are all molecules with lone pairs polar?
Replies: 7
Views: 18006

### Re: Are all molecules with lone pairs polar?

It also affects the symmetry of specific molecules. For example, NH3 is tetrahedral shaped and would be nonpolar if it were trigonal polar with H on all sides, but the lone pair does not allow the symmetry, turning it into a non-symmetrical tetrahedral arrangement.
Mon Oct 28, 2013 3:18 pm
Forum: Dipole Moments
Topic: Certain Structures and Polarity
Replies: 3
Views: 733

### Re: Certain Structures and Polarity

504047082 wrote:Are there any structures that are usually polar/non-polar? Are there any quick rules of thumb we should know that would help us quickly figure out the polarity?

Not really structures, but shapes that are symmetrical (that have the same atoms on each side as well) are generally nonpolar.
Sun Oct 27, 2013 3:30 pm
Forum: Hybridization
Topic: Hybridization of 3rd C in CH2CHCN
Replies: 2
Views: 3159

### Re: Hybridization of 3rd C in CH2CHCN

I think the carbon in question has a triple bond with the nitrogen, since the answer key says that nitrogen has only 1 lone pair. This would create a linear arrangement for the CCN:
Sun Oct 27, 2013 3:27 pm
Forum: Ionic & Covalent Bonds
Topic: Are we required to know all exceptions of the periodic table
Replies: 1
Views: 438

### Re: Are we required to know all exceptions of the periodic t

Probably not, for now. I think the important thing is probably to understand the concepts behind the exceptions that we learned.
Sun Oct 27, 2013 3:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Chapter 2 #57a
Replies: 1
Views: 325

### Re: Chapter 2 #57a

I'm not too sure about the properties of radicals and their formal charges, but my theory is that since oxygen is more electronegative than chlorine, ClO exists without a balanced formal charge.
Sun Oct 27, 2013 3:23 pm
Forum: Resonance Structures
Topic: Answer to resonance structures of anthracene incorrect?
Replies: 2
Views: 1129

### Re: Answer to resonance structures of anthracene incorrect?

Looks like an error to me. Carbon cannot have an expanded octet.
Sun Oct 27, 2013 3:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 3.19 and determining position of electrons
Replies: 2
Views: 592

### Re: 3.19 and determining position of electrons

In a molecule that is a tetrahedral arrangement, there is no "across from" for the chlorines. No matter where you put the chlorines, they will be next to another chlorine.
Sun Oct 27, 2013 3:14 pm
Forum: Formal Charge and Oxidation Numbers
Topic: d block element charges
Replies: 1
Views: 487

### Re: d block element charges

D-block elements usually have a +2 charge because their valence electrons are just the s-orbital electrons.
Fri Oct 25, 2013 5:21 pm
Forum: Resonance Structures
Topic: Number of Resonance Structures?
Replies: 2
Views: 493

### Re: Number of Resonance Structures?

I think there may be a mathematical way, but there would be too many combinations to memorize with all the different groups of elements, etc. Generally, we'll probably be asked to draw resonance for something that just has 2 or 3 different structures.
Fri Oct 25, 2013 11:48 am
Forum: Electronegativity
Topic: Polarity of Compound with different terminal atoms
Replies: 2
Views: 1025

### Re: Polarity of Compound with different terminal atoms

Even if the difference isn't very great, there will still be a small, however slight, dipole moment on some of these molecules. Generally, non-symmetric linear molecules, or tetrahedral molecules that have 3 of the same terminal atoms and 1 different one will be polar.
Fri Oct 25, 2013 11:46 am
Forum: Ionic & Covalent Bonds
Topic: In what order do electrons get removed?
Replies: 7
Views: 17736

### Re: In what order do electrons get removed?

Electrons are typically removed from the valence shells, which are the highest s and p orbitals. Also, Hund's rule still applies here, but backwards. Electrons will be removed from their orbitals until all of them are unpaired, and then the unpaired ones will be removed.
Fri Oct 25, 2013 11:44 am
Forum: Ionic & Covalent Bonds
Topic: How do you bracket Ionic Bonds
Replies: 1
Views: 1263

### Re: How do you bracket Ionic Bonds

Usually, brackets go around Lewis structures that have an overall charge. The simplest would be something like [H]+ [::F::]- as a Lewis structure.
Fri Oct 25, 2013 11:42 am
Forum: Hybridization
Topic: Hybridization of central atom in O3
Replies: 4
Views: 14613

### Re: Hybridization of central atom in O3

That is correct. Double and triple bonds all count as one area of electron density.
Thu Oct 24, 2013 5:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 3.11 d) N2O
Replies: 2
Views: 829

### Re: 3.11 d) N2O

It is more important to satisfy octets rather than the formal charge, I believe.

For N2O, I have :N:::N:O::: so that oxygen has a formal charge of -1 and nitrogen has a formal charge of +1, which makes sense because oxygen has higher electronegativity. This way an octet can be filled
Wed Oct 23, 2013 3:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Should we put the molecular shape or arrangement?
Replies: 1
Views: 328

### Should we put the molecular shape or arrangement?

Some questions ask for the geometry of a specific molecule. If the molecule is SF4, which shows a seesaw shape and a trigonal bipyramidal arrangement, what should we write for the geometry when asked? (My TA said we should write both but specify which is which)
Mon Oct 21, 2013 9:30 am
Forum: Lewis Structures
Topic: Single/Double bond convention
Replies: 4
Views: 600

### Re: Single/Double bond convention

Edit: My answer was incorrect.
Tue Oct 15, 2013 3:58 pm
Forum: SI Units, Unit Conversions
Topic: Why is g mol written with a negative 1 (g mol^-1)
Replies: 4
Views: 12032

### Re: Why is g mol written with a negative 1 (g mol^-1)

Is there a particular reason that one is preferable toward the other? For instance, when would we use g/mol rather than g*mol^-1 and vice versa?

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