Search found 30 matches

by Andrew Lam 3B
Sat Dec 01, 2018 12:22 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 209
Views: 101141

Re: Saying Thank You to Dr. Lavelle

Thank you Dr. Lavelle for making your lectures informative and engaging. It has been easy to keep up with the material presented and I am looking forward to 14B next quarter.
by Andrew Lam 3B
Sat Dec 01, 2018 12:14 pm
Forum: Sigma & Pi Bonds
Topic: Number of Sigma and Pi Bonds
Replies: 6
Views: 330

Re: Number of Sigma and Pi Bonds

pi bonds form between p orbitals -- there are 3 of them per atom
by Andrew Lam 3B
Sat Dec 01, 2018 12:06 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Equilibrium Constants
Replies: 2
Views: 80

Re: Equilibrium Constants

Strong acids/base reactions go so far towards dissociation we assume they completely dissociate, so no equilibrium constant needs to be solved for. (There are basically no reactants left)
by Andrew Lam 3B
Tue Nov 27, 2018 10:31 am
Forum: Hybridization
Topic: Pi bonds
Replies: 3
Views: 90

Re: Pi bonds

Pi bonds bond above and below the molecule and lock the molecule in place, preventing rotation unlike sigma bonds who bond at one point in the center
by Andrew Lam 3B
Tue Nov 27, 2018 9:57 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Double Bonds as Regions of Electron Density
Replies: 5
Views: 79

Re: Double Bonds as Regions of Electron Density

Single, Double, Triple bonds all counts as one region of electron density.
by Andrew Lam 3B
Tue Nov 27, 2018 9:56 am
Forum: Hybridization
Topic: Just Kind of Confused
Replies: 13
Views: 216

Re: Just Kind of Confused

I think it's just more of a stylistic thing and personal preference.
by Andrew Lam 3B
Tue Nov 27, 2018 9:46 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw or Square Planar
Replies: 3
Views: 143

Re: Seesaw or Square Planar

AX4E is Seesaw (dsp3), AX4E2 is Square Planar (d2sp3)
by Andrew Lam 3B
Tue Nov 27, 2018 9:45 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: test #3
Replies: 14
Views: 505

Re: test #3

Dimagnetic elements have no unpaired electrons, while paramagnetic elements have at least 1.
by Andrew Lam 3B
Tue Nov 27, 2018 9:39 am
Forum: Hybridization
Topic: s-character
Replies: 6
Views: 446

Re: s-character

sp: 1/2
sp2: 1/3
sp3: 1/4
dsp3: 1/5
d2sp3: 1/6

It's the ratio of the orbitals.
by Andrew Lam 3B
Sun Nov 18, 2018 11:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles for H2O
Replies: 8
Views: 831

Re: Bond Angles for H2O

Lone pairs take up more space than bonding pairs, so instead of 109.5 for tetrahedral you get 104.5 and bent.
by Andrew Lam 3B
Sun Nov 18, 2018 11:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair influence on shape
Replies: 12
Views: 225

Re: lone pair influence on shape

Lone pairs take up more space than bonding pairs, depressing the bond angle.
by Andrew Lam 3B
Sun Nov 18, 2018 11:18 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 16
Views: 237

Re: Bond Angles

It would probably be safe to know the most common ones just in case they come up on a test.
by Andrew Lam 3B
Sun Nov 11, 2018 3:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Nonpolar Molecules
Replies: 4
Views: 114

Re: Polar and Nonpolar Molecules

The water molecules are more attracted to one another (dipoles) than to the oil molecules. The oil molecules are said to be hydrophobic and do not mix with water for this reason.
by Andrew Lam 3B
Sun Nov 11, 2018 3:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs on Neighboring Atoms
Replies: 2
Views: 59

Re: Lone Pairs on Neighboring Atoms

Lone pairs on neighboring atoms would repel one another because they are all negative (only electrons form lone pairs). This weakens the bond in question.
by Andrew Lam 3B
Sun Nov 11, 2018 12:45 pm
Forum: Bond Lengths & Energies
Topic: VSEPR Model for Water
Replies: 3
Views: 102

Re: VSEPR Model for Water

The oxygen molecule on water has 2 lone pairs that cause the bond angle to be slightly depressed to around 109.5; this is called a bent configuration.
by Andrew Lam 3B
Sun Nov 04, 2018 10:17 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and Lewis Structures
Replies: 5
Views: 132

Re: Formal Charge and Lewis Structures

Generally the most stable configuration is one where the formal charge is minimized on all the atoms involved. Usually you don't have to draw them but it can be helpful if a test question were to ask of the two lewis structures which one is favored.
by Andrew Lam 3B
Sun Nov 04, 2018 10:11 pm
Forum: Sigma & Pi Bonds
Topic: Midterm1
Replies: 10
Views: 331

Re: Midterm1

It shows up on a lot of old midterms but I'm guessing they had already gotten to hybridization by that point. I don't think it would show up on tomorrow's midterm (that would be a really unfair question)
by Andrew Lam 3B
Sun Nov 04, 2018 10:09 pm
Forum: Ionic & Covalent Bonds
Topic: Chem Midterm
Replies: 13
Views: 216

Re: Chem Midterm

Do you guys know how many points total you can get taken off of the midterm if you miss sig figs and units, but get all of the math/concepts right? Looking at previous midterms, you usually lose 1 or 2 points per problem for sig figs or units if you mess either up. So for a question say Q4A, Q4B, a...
by Andrew Lam 3B
Tue Oct 23, 2018 2:03 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Exercise 2.29
Replies: 10
Views: 1184

Re: Exercise 2.29

For Problem 2.49 "Predict the number of valence electrons present in each of the following atoms (include the outermost d-electrons: (a) N; (b) Ag; (c) Nb; (d) W." What trend are we expected to see in order to identify the number of valence electrons? The atomic number? Is there also some...
by Andrew Lam 3B
Tue Oct 23, 2018 2:00 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Exercise 2.29
Replies: 10
Views: 1184

Re: Exercise 2.29

In 2.29 part c), I don't understand why the maximum number of electrons is 8 if n=2. Can someone please explain? At energy level 2, there are two possible subshells: s and p. (Remember that 2d and 2f do not exist). The s subshell can hold 2 electrons, while the 3 p orbitals combined hold 6 electron...
by Andrew Lam 3B
Tue Oct 23, 2018 1:59 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Exercise 2.29
Replies: 10
Views: 1184

Re: Exercise 2.29

For Exercise 2.29 (Chapter 2 The Quantum Mechanics in Action: Atoms) How many electrons can have the following quantum numbers in an atom: a) n = 2, l = 1 b) n = 4, l = 2, ml = -2 c) n = 2 d) n = 3, l = 2, ml = +1 Does anyone know how to solve this problem? Thank you in advance The question varies i...
by Andrew Lam 3B
Sat Oct 20, 2018 2:43 pm
Forum: DeBroglie Equation
Topic: Wave properties of large particles
Replies: 3
Views: 88

Re: Wave properties of large particles

The wave properties do exist for relatively large objects, but those wavelengths are so small we do not have equipment that can detect waves in the 10^-35 spectrum.
by Andrew Lam 3B
Sat Oct 20, 2018 2:41 pm
Forum: Quantum Numbers and The H-Atom
Topic: ml Quantum Number
Replies: 4
Views: 121

Re: ml Quantum Number

ml is used to describe the individual orbital within a subshell.

For l = 0 (s orbital), then the only ml possible is 0 (there is only one s orbital).
For l = 1 (p orbital), you can have ml = -1 (px), 0 (py), or 1 (pz), and so forth for other orbitals.
by Andrew Lam 3B
Sat Oct 20, 2018 2:39 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shielding [ENDORSED]
Replies: 15
Views: 711

Re: Shielding [ENDORSED]

The p-orbital experiences less pull from the nucleus because some of the repulsion from s-orbital electrons are also affecting it. Thus, we need something called effective nuclear charge to describe the binding strength of electrons. They are the same energy level (in the case of 2s and 2p) but are ...
by Andrew Lam 3B
Sat Oct 13, 2018 8:54 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: diatomic elements
Replies: 12
Views: 813

Re: diatomic elements

Diatomics exist to share electrons covalently and achieve a lower energy state.

HOFBrINCl is a metonym to remember the diatomics:
H- Hydrogen
O- Oxygen
F- Fluorine
Br- Bromine
I- Iodine
N- Nitrogen
Cl- Chlorine
by Andrew Lam 3B
Sat Oct 13, 2018 8:52 pm
Forum: Trends in The Periodic Table
Topic: electron affinity [ENDORSED]
Replies: 15
Views: 501

Re: electron affinity [ENDORSED]

Atoms with low electron affinity (i.e. alkali metals) lose electrons far more easily to have a full valence shell whereas it is far easier for a halogen (say Fluorine) to pick up an electron and fill its valence shell. Thus, we say halogens have a high electron affinity.
by Andrew Lam 3B
Mon Oct 08, 2018 4:27 pm
Forum: Properties of Light
Topic: Quanta & Photons
Replies: 5
Views: 112

Re: Quanta & Photons

In essence, you can never have light that strikes in 1.2 photons, 5.64 photons, etc. The particle nature of light only travels in whole number of "packets".
by Andrew Lam 3B
Sun Sep 30, 2018 4:21 pm
Forum: Molarity, Solutions, Dilutions
Topic: Question E16 - Transition Metal Charge
Replies: 4
Views: 128

Re: Question E16 - Transition Metal Charge

Silver generally is found in the +1 oxidation state.

Other ones of note are Iron being +2 or +3, copper being +1, etc.
by Andrew Lam 3B
Sun Sep 30, 2018 12:18 pm
Forum: Molarity, Solutions, Dilutions
Topic: Study Module Post-assessment Question
Replies: 5
Views: 173

Re: Study Module Post-assessment Question

MinitialVinitial = MfinalVfinak

Minitial = 0.2109 M
Vinitial = 0.02 L (Only 20.0 mL is transferred)
Vfinal = 0.250 L

Solve for Mfinal, which should be 1.69 x 10-2 M
by Andrew Lam 3B
Sun Sep 30, 2018 12:09 pm
Forum: Empirical & Molecular Formulas
Topic: Mutiplying by a number
Replies: 3
Views: 111

Re: Mutiplying by a number

If it looks like or is close to a fraction, multiply by its inverse to clear a fraction
(e.g. x.3333 multiply by 3, x.25 multiply by 4, x.2 multiply by 5, x.5 multiply by 2, x.75 multiply by 4/3)

If its close to a whole number, just round up (x.9545 just round to the next number)

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