Search found 52 matches

by Aadil Rehan 1D
Sat Dec 07, 2019 7:05 pm
Forum: Photoelectric Effect
Topic: Dino Nuggets question 8b
Replies: 3
Views: 54

Re: Dino Nuggets question 8b

Unless you provide the formulas/conversions you used, it will be difficult to help, but in the meantime, here's a couple points to consider. Are all your units correct? You need to convert the work function of sodium to kJ/electron at the very least. Also, are you keeping in mind that the energy of ...
by Aadil Rehan 1D
Sat Dec 07, 2019 6:57 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Stoichiometric Point
Replies: 2
Views: 21

Re: Stoichiometric Point

Not entirely sure what the question is asking, as the stoichiometric point is when there is an equal number of moles of acid and base in a solution, which by definition means it is neutral. If the moles of acid equal the moles of base, the solution has a pH of 7.
by Aadil Rehan 1D
Sat Dec 07, 2019 6:54 pm
Forum: Hybridization
Topic: Marshmallows #17 - hybridization in pi bonds
Replies: 2
Views: 22

Re: Marshmallows #17 - hybridization in pi bonds

My guess is that it's a typo. Pi bonds result from the overlapping of p orbitals specifically (think of it like two infinity symbols, one on top of the other) so the pi bond should only have p character.
by Aadil Rehan 1D
Sat Dec 07, 2019 2:36 pm
Forum: General Science Questions
Topic: Tightly bound
Replies: 2
Views: 22

Re: Tightly bound

Smaller atoms are also usually more tightly bound, as the internuclear distance is smaller.
by Aadil Rehan 1D
Sat Dec 07, 2019 2:31 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 3778

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

For number 21) you need to essentially "give back" an electron pair to the ligands bonded to the central atom to find their formal charge. Does this apply to all ligands and coordination compounds? Like B12 for example? I would assume so, but for the dashed-line bonds. For B12, a few webs...
by Aadil Rehan 1D
Wed Nov 27, 2019 6:13 pm
Forum: Biological Examples
Topic: EDTA
Replies: 8
Views: 46

Re: EDTA

EDTA is also made into a buffer with Tris (tris(hydroxymethyl)aminomethane), which is then used to stabilize DNA in solution.
by Aadil Rehan 1D
Wed Nov 27, 2019 6:07 pm
Forum: Conjugate Acids & Bases
Topic: What are conjugates?
Replies: 3
Views: 24

Re: What are conjugates?

It's also important to note that the stability of the conjugate base is a good indicator of the strength of the acid. Cl-, Br-, I-, for example, are all relatively stable anions, so their conjugate acids (HCl, HBr, HI) are strong.
by Aadil Rehan 1D
Wed Nov 27, 2019 5:44 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds other than Be, Al, Ga, Sn, Pb, and Sb
Replies: 3
Views: 17

Re: Amphoteric Compounds other than Be, Al, Ga, Sn, Pb, and Sb

Good ways to check if something is amphoteric:
- Does it have at least 1 hydrogen to donate?
- Is it negative or neutral? (more likely to allow a hydrogen to bond)
- Does it have lone pairs / can it form another bond?
by Aadil Rehan 1D
Wed Nov 27, 2019 5:39 pm
Forum: Air Pollution & Acid Rain
Topic: other biological examples
Replies: 4
Views: 207

Re: other biological examples

Might also be important to know that carbonic acid is formed by the reaction of water and CO2, which happen to be the products of cellular respiration.
by Aadil Rehan 1D
Wed Nov 27, 2019 5:30 pm
Forum: Lewis Acids & Bases
Topic: oxides
Replies: 3
Views: 19

Re: oxides

Oxides are generally strong bases, the O2- anion is a pretty powerful proton acceptor.
by Aadil Rehan 1D
Sun Nov 24, 2019 11:47 pm
Forum: Industrial Examples
Topic: Difference between biological and industrial examples?
Replies: 3
Views: 41

Re: Difference between biological and industrial examples?

Biological: used in living beings - animal cells, plant cells, and the like. Think hemoglobin, or vitamin B12.
Industrial: used in factories or by companies in marketed products. I think bismuth subsalicylate, or Pepto-Bismol, is an example of this.
by Aadil Rehan 1D
Sun Nov 24, 2019 11:40 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Example of Acetic Acid as a weak acid
Replies: 2
Views: 20

Re: Example of Acetic Acid as a weak acid

You can also think of as the acetate anion, CH3COO-, is not very stable, and prefers being the acid form, CH3COOH. Whereas the strong acids have a stable conjugate base.
by Aadil Rehan 1D
Sun Nov 24, 2019 11:35 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong acids vs weak acids
Replies: 8
Views: 31

Re: Strong acids vs weak acids

The mnemonic I use to remember strong acids for me is SPN IBC - Sulfuric Perchloric Nitric, then Hydroiodidic, Hydrobromic, Hydrochloric.
by Aadil Rehan 1D
Sun Nov 24, 2019 11:33 pm
Forum: Biological Examples
Topic: Transition Metals and Oxidation States
Replies: 1
Views: 22

Re: Transition Metals and Oxidation States

At least in the case of plant cells, metals with many oxidation states are located in the center of the photosystem complexes. This allows for electrons to be excited more easily and transfer energy to electron carriers during the light reactions.
by Aadil Rehan 1D
Sun Nov 24, 2019 11:28 pm
Forum: Naming
Topic: Di-, Tri-, Tetra- vs Bis-, Tris-, Tetrakis-
Replies: 11
Views: 49

Re: Di-, Tri-, Tetra- vs Bis-, Tris-, Tetrakis-

Ligands are the ones within the coordination sphere of the central atom.
by Aadil Rehan 1D
Sun Nov 17, 2019 1:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles in 2E.7
Replies: 1
Views: 16

Bond Angles in 2E.7

2E.7 asks for the shape and bond angles for the molecule SOCl 2 . Spoiler alert, it's trigonal pyramidal, and the answer key gives the bond angles as slightly less than 109.5 degrees. I understand that this is because of the repulsion of the lone pair in the axial position, but is it possible that t...
by Aadil Rehan 1D
Sat Nov 16, 2019 4:31 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 5
Views: 30

Re: Polarizability

Another thing to look out for is the presence of electronegative atoms in the molecule. The most common offenders are Fluorine, Oxygen, and Nitrogen, but most of the right side of the periodic table count. If a compound is all carbons and hydrogens, it's nonpolar.
by Aadil Rehan 1D
Sat Nov 16, 2019 4:29 pm
Forum: Dipole Moments
Topic: 2E.2 Determing strongest dipole moment between resonance structures
Replies: 2
Views: 16

Re: 2E.2 Determing strongest dipole moment between resonance structures

The more polar a molecule, the stronger the dipole moment. Dipoles moments arise from regions of high electron density, and when the chlorine atoms are close to each other, the electron density is higher. Thus, I believe that the 6-carbon ring with 2 Chlorine atoms attached to 2 directly adjacent ca...
by Aadil Rehan 1D
Sat Nov 16, 2019 4:26 pm
Forum: Bond Lengths & Energies
Topic: Bond Strengths
Replies: 3
Views: 19

Re: Bond Strengths

If I'm not mistaken, I think it means that bonds between two of a particular type of atom are about the same strength - for example, the C-C bond in ethane has the same strength as a C-C bond in butane. Thus, bond strengths are (approximately) transferrable.
by Aadil Rehan 1D
Sat Nov 16, 2019 3:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: How to study for VSEPR?
Replies: 9
Views: 78

Re: How to study for VSEPR?

I, personally, am making a chart with the format that Prof. Lavelle discussed in class (i.e. AXnEn), as well as the shape and the bond angles.
by Aadil Rehan 1D
Sat Nov 16, 2019 3:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining VSEPR Model
Replies: 3
Views: 19

Re: Determining VSEPR Model

A "proper" (i.e. lowest-energy) Lewis structure has the formal charges done correctly. The shape that the molecule assumes in nature will be that of lowest energy. So technically, yes, you should take formal charges into account when naming shape, but no more than you would for making a no...
by Aadil Rehan 1D
Fri Nov 08, 2019 7:02 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: Polarizability and States
Replies: 3
Views: 36

Re: Polarizability and States

I think gaseous atoms are the most polarizable, simply based on the fact that atoms and their electrons are most mobile in the gas state.
by Aadil Rehan 1D
Fri Nov 08, 2019 6:59 pm
Forum: Bond Lengths & Energies
Topic: Sigma Pi
Replies: 2
Views: 22

Re: Sigma Pi

According to Brilliant.org, "A sigma bond, σ, resembles a similar "s" atomic orbital, and a pi bond, π, has the same orbital symmetry of the p orbital (again, in both cases when viewed down the bond axis)." So I'd assume that's where the convention comes from.
by Aadil Rehan 1D
Fri Nov 08, 2019 6:57 pm
Forum: Dipole Moments
Topic: Fluctuating Dipoles
Replies: 2
Views: 16

Re: Fluctuating Dipoles

A negative charge can be thought of as a large concentration of negative charge clustered around a small area in the atom. As the distribution of electrons change, the charges will change as well. Some regions, by virtue of not having as high of electron density, will take on a partial positive char...
by Aadil Rehan 1D
Fri Nov 08, 2019 6:52 pm
Forum: Bond Lengths & Energies
Topic: negative Ep
Replies: 5
Views: 30

Re: negative Ep

I think it's just a matter of convention. From what I've read though, at least in the realm of electrostatics, potential energy is usually the work that must be done to move an object a certain distance. if the potential energy is negative, it's entirely possible that it means that no work has to be...
by Aadil Rehan 1D
Fri Nov 08, 2019 6:46 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Hydrogen bonding in DNA
Replies: 2
Views: 11

Re: Hydrogen bonding in DNA

C-G pairs have three hydrogen bonds as opposed to A-T's two. I think the relative strength has to do with the lone pair donors and how they vary between the nitrogenous bases.
by Aadil Rehan 1D
Sun Nov 03, 2019 11:50 pm
Forum: Resonance Structures
Topic: Bond lengths
Replies: 11
Views: 61

Re: Bond lengths

Resonant compounds have more delocalized electrons, so they're kind of swooshing around the bonds all the time. The bond length we have is an average of what is measured.
by Aadil Rehan 1D
Sun Nov 03, 2019 11:49 pm
Forum: Ionic & Covalent Bonds
Topic: Carbon Bonding
Replies: 5
Views: 31

Re: Carbon Bonding

In very rare situations, carbon forms 3 bonds and has a temporary positive charge. However, it's only in intermediates, and we probably won't see it for a while, if at all.
by Aadil Rehan 1D
Sun Nov 03, 2019 11:44 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds and unpaired electrons
Replies: 2
Views: 24

Re: Covalent Bonds and unpaired electrons

Good observation! It's usually because that number of bonds fills all the valence shells. Let's take Carbon as an example. It's 1s 2 2s 2 2p 2 . It "wants" 4 electrons to fill its outer valence shell, but it's not electronegative enough to form ionic bonds. It can get those electrons, howe...
by Aadil Rehan 1D
Sun Nov 03, 2019 11:36 pm
Forum: Electronegativity
Topic: Ionic or covalent?
Replies: 17
Views: 102

Re: Ionic or covalent?

If a compound is made from a metal and a non-metal, its bonding will usually be ionic and if it’s made from two non-metals, its bonding should be covalent how do metalloids play into that, though? good question, from what I've read metalloids have external properties of a metal (or can be induced t...
by Aadil Rehan 1D
Sun Nov 03, 2019 11:26 pm
Forum: Bond Lengths & Energies
Topic: Bonding
Replies: 7
Views: 48

Re: Bonding

Not an exception to the octet rule, but to the typical electron configuration pattern - chromium and copper. They're [Ar]3d54s1 and [Ar]3d104s1 respectively, you just have to know that a half-filled or full d is more stable than a full s subshell.
by Aadil Rehan 1D
Sun Oct 27, 2019 11:59 pm
Forum: Resonance Structures
Topic: Stability from Resonance Structures
Replies: 2
Views: 19

Re: Stability from Resonance Structures

Resonant molecules are in general more stable.
by Aadil Rehan 1D
Sun Oct 27, 2019 11:59 pm
Forum: Electronegativity
Topic: Radius
Replies: 13
Views: 429

Re: Radius

More shielding = greater radius but also less electronegativity, due to the weaker nuclear pull.
by Aadil Rehan 1D
Sun Oct 27, 2019 11:58 pm
Forum: Sigma & Pi Bonds
Topic: Single vs. Double bonds
Replies: 15
Views: 77

Re: Single vs. Double bonds

Fun fact: the shorter double bonds means that the stereochemistry (shape chemistry) is also greatly simplified.
by Aadil Rehan 1D
Sun Oct 27, 2019 11:57 pm
Forum: Sigma & Pi Bonds
Topic: Which bond would break first.
Replies: 15
Views: 575

Re: Which bond would break first.

jlinwashington1B wrote:How would we be able to distinguish between the two? I know pie bonds show polarity, but I need a bit more clarification of sigma bonds>


Probably based on the length and energy of the bonds.
by Aadil Rehan 1D
Sun Oct 27, 2019 11:56 pm
Forum: Resonance Structures
Topic: Formal Charge
Replies: 5
Views: 33

Re: Formal Charge

Nope, "formal" is just a formality, if you will, to refer to the charge of the atom within the molecule.
by Aadil Rehan 1D
Sun Oct 20, 2019 11:45 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Minimum Uncertainty
Replies: 2
Views: 30

Re: Minimum Uncertainty

Nope, just means to solve the problem normally. The uncertainty we usually calculate is a minimum value anyway - it can be higher.
by Aadil Rehan 1D
Sun Oct 20, 2019 11:44 pm
Forum: *Shrodinger Equation
Topic: wavefunctions & orbitals relationship?
Replies: 5
Views: 53

Re: wavefunctions & orbitals relationship?

Simply put, wave functions describe behavior within an orbital.
by Aadil Rehan 1D
Sun Oct 20, 2019 11:26 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1F.19
Replies: 3
Views: 21

Re: 1F.19

To elaborate, the lower ionization energy is partially because the valence electrons are further from the nucleus, meaning the attraction is less.
by Aadil Rehan 1D
Sun Oct 20, 2019 11:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: electron spin
Replies: 4
Views: 35

Re: electron spin

As far as I'm aware, varying spins can be understood as phase-shifts in the sinusoidal wavefunction for electrons.
by Aadil Rehan 1D
Sun Oct 20, 2019 11:09 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 8
Views: 69

Re: Ionization Energy

Yeah, think of it as the shielding of the electron cloud decreasing, and thus the positive nucleus is able to exert a stronger force.
by Aadil Rehan 1D
Mon Oct 14, 2019 12:02 am
Forum: Properties of Light
Topic: What is Threshold Energy?
Replies: 9
Views: 46

Re: What is Threshold Energy?

Ionization energy refers to the energy needed to remove an electron from a gas, vs. threshold energy for a solid.
by Aadil Rehan 1D
Sun Oct 13, 2019 10:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1A.11
Replies: 2
Views: 19

Re: 1A.11

I realize that was kind of vague so here's my attempt at a more concrete explanation. Let's say we have a hydrogen atom that is currently at the energy state n = 2. It drops to energy state n = 1, emitting 50 joules. (this number, and the following, were randomly selected and have no basis in fact.)...
by Aadil Rehan 1D
Sun Oct 13, 2019 9:59 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1A.11
Replies: 2
Views: 19

Re: 1A.11

This was difficult for me to understand too. As far as I understand, each series represents a series of emission lines as an H atom goes from an arbitrary larger quantum number to a specific, smaller quantum number. For example, the Lyman series represents an H atom going from energy level n = 2,3,4...
by Aadil Rehan 1D
Sun Oct 13, 2019 9:40 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 3
Views: 28

Re: Photoelectric Effect

To be exact, some semiconductors (i.e. silicon) have some properties of metal, and can thus also exhibit the photoelectric effect. Would probably take a lot more energy, though.
by Aadil Rehan 1D
Sun Oct 13, 2019 9:37 pm
Forum: Trends in The Periodic Table
Topic: electronegativity
Replies: 10
Views: 339

Re: electronegativity

I think you may be thinking of electron affinity, which refers to the amount of energy released when an electron is added to a neutral atom. Same trend, but not interchangeable.
by Aadil Rehan 1D
Wed Oct 02, 2019 11:53 pm
Forum: Balancing Chemical Reactions
Topic: Fundamental H5 D
Replies: 3
Views: 30

Re: Fundamental H5 D

I usually start by looking for the minimum coefficient that something has to be multiplied by - for example, since there's 4 phosphorus atoms on the right side, I know that Fe2P has to have a coefficient of at least 4. It can be reverse-solved from there, usually.
by Aadil Rehan 1D
Wed Oct 02, 2019 11:48 pm
Forum: Empirical & Molecular Formulas
Topic: Chapter F Problem 15
Replies: 4
Views: 50

Re: Chapter F Problem 15

You don't need molar mass to calculate the empirical, only the molecular. Assume a 100g sample to find empirical.
by Aadil Rehan 1D
Wed Oct 02, 2019 11:44 pm
Forum: Balancing Chemical Reactions
Topic: Naming ionic/ molecular compounds
Replies: 7
Views: 86

Re: Naming ionic/ molecular compounds

While I'm fairly sure we won't have to worry about that for most of 14A, might be a good call to take a look at some lists of polyatomic ions online and start to memorize them - it makes a lot of problems a lot quicker. I also like to make dumb mnemonics: for example: the carbonate ion is CO 3 , whi...
by Aadil Rehan 1D
Wed Oct 02, 2019 11:38 pm
Forum: Empirical & Molecular Formulas
Topic: Question about Theoretical Yield
Replies: 8
Views: 84

Re: Question about Theoretical Yield

I usually find it quicker to just solve to moles first, then convert to grams with the smaller amount. I think the comparison should be done in moles anyway, given that most ratio-comparison things are done with moles.
by Aadil Rehan 1D
Wed Oct 02, 2019 11:30 pm
Forum: Balancing Chemical Reactions
Topic: Figuring Out State Symbols
Replies: 3
Views: 50

Re: Figuring Out State Symbols

It's also good to keep the diatomic elements in mind - can be remembered with the abbreviation "HOFBrINCl" (Hydrogen, Oxygen, Fluorine, Bromine, Iodine, Nitrogen, Chlorine.) Apart from special cases of pressure and/or temperature, when you see a pure form of one of these elements, it shoul...
by Aadil Rehan 1D
Wed Oct 02, 2019 11:27 pm
Forum: Limiting Reactant Calculations
Topic: Cases in which actual product is greater than theoretical?
Replies: 3
Views: 49

Cases in which actual product is greater than theoretical?

I was curious if there are any situations under which the actual product you get from an experiment is greater than the theoretical yield (which would give you over 100% yield.) I've read that this can be the case if a product is still damp when weighed. Can you guys think of any others?

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