Search found 72 matches

by MaanasO 1A
Tue Mar 12, 2019 9:13 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Converting
Replies: 2
Views: 54

Re: Converting

Ok so when you have a reaction at equilibrium, k[R]/k'[P] = 1 => k/k' = K (the equilibrium constant).

You can use this substitution when your rate determining step contains an intermediate.
by MaanasO 1A
Tue Mar 12, 2019 9:11 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equilibrium vs. steady-state
Replies: 4
Views: 67

Re: Pre-equilibrium vs. steady-state

You use pre-equilibrium when you have an intermediate listed in your slow step. You don't use steady state because it's super mathy and he never taught it to us in class.
by MaanasO 1A
Tue Mar 12, 2019 9:10 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and Heat
Replies: 1
Views: 180

Re: Entropy and Heat

Outside entropy decreases and interior entropy increases. The change should be greater outside because it has a lower temperature so q/T is greater outside than inside.
by MaanasO 1A
Wed Mar 06, 2019 8:02 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th Edition #6.O.3
Replies: 1
Views: 34

Re: 7th Edition #6.O.3

Nah because when you add the voltages, you flip the sign for the reaction that is oxidized. So for your example, you will have -0.42 + 1.18 > 0, so that means the overall reaction will be spontaneous.
by MaanasO 1A
Wed Mar 06, 2019 8:00 am
Forum: General Rate Laws
Topic: Unit for reaction rates
Replies: 4
Views: 85

Re: Unit for reaction rates

The reaction rate is based on change in M w/ respect to time, so you'll need M/s as the final units.
by MaanasO 1A
Wed Mar 06, 2019 6:43 am
Forum: General Rate Laws
Topic: Reaction Order
Replies: 4
Views: 79

Re: Reaction Order

The final output should have the units M/s. So if you have higher than a 1st order reaction, you'll have extra M multiplied together => the k will have multiple 1/M to cancel everything out.
by MaanasO 1A
Wed Feb 27, 2019 11:46 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G at boiling point
Replies: 2
Views: 92

Re: Delta G at boiling point

This is assuming constant temperature and pressure. Sooooooooooooooooo....:

del(S) = q/T = del(H)/T
T * del(S) = T * del(H)/T = del(H)
del(G) = del(H) - T * del(S) = del(H) - del(H) = 0

Hope that helps!
by MaanasO 1A
Wed Feb 27, 2019 11:43 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H half rxns
Replies: 1
Views: 47

Re: H half rxns

In this case, HCL completely dissolves into H+ and Cl-, so you can ignore the Cl- for the time being. That's why they only use H+.
by MaanasO 1A
Wed Feb 27, 2019 11:38 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Thermodynamic Stability
Replies: 2
Views: 60

Re: Thermodynamic Stability

Nah I think that stuff's outside the syllabus. We just have to be able to identify whether a molecule stable based on its Gf.
by MaanasO 1A
Wed Feb 20, 2019 5:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs concept
Replies: 7
Views: 138

Re: Gibbs concept

Danny Elias Dis 1E wrote:Can someone explain what is happening on a physical level when deltaG = 0 (the Gibbs free energy is at equilibrium)?


The reaction has reached equilibrium, so neither reaction is more favored over the other. Therefore no net energy is available to be used to drive the forward or reverse reaction.
by MaanasO 1A
Wed Feb 20, 2019 5:07 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibb's free energy Units
Replies: 4
Views: 70

Re: Gibb's free energy Units

When converted from G to K (equilibrium constant), make sure you deal with J not kJ. Both are fine as answers unless specified otherwise, but make sure to check whether the units cancel properly in calcs.
by MaanasO 1A
Wed Feb 20, 2019 5:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells
Replies: 7
Views: 94

Re: Galvanic Cells

Hi Dayna!

So the galvanic cell is that diagram Lavelle drew on the board. It's the basis for a battery. It's neither a biological cell or a pocket of space.

Hope that helps!
by MaanasO 1A
Wed Feb 13, 2019 12:33 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: Positional (residual) entropy
Replies: 1
Views: 187

Re: Positional (residual) entropy

Hi Hailey!

Residual entropy is a property that arises based on the number of macrostates [that all have equal energies] that are possible in a given system. It is the value that's given by S = kb[ln(W)].

Hope that helps!
by MaanasO 1A
Wed Feb 13, 2019 12:32 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Heating water + cooling
Replies: 2
Views: 80

Re: Heating water + cooling

Hi Sarah! The heat gained by the ice [q(ice)] is equal to the heat LOST by the water [-q(water)]. If you add the negative sign to the heat of water, the q value comes out as positive (because of the double negative). Their magnitudes are the same, so it's not technically incorrect for your TA to wri...
by MaanasO 1A
Wed Feb 13, 2019 12:29 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Delta S equations
Replies: 3
Views: 115

Re: Delta S equations

Hi Katherine! dS = q/t when you're dealing with a reversible process. dS = nRln(Vf/Vi) when the process is isothermal. dS = nCln(Tf/Ti) when there's a change in temperature associated with the change in entropy. Your C value will change based on whether your volume (Cv) or pressure (Cp) are constant...
by MaanasO 1A
Fri Feb 08, 2019 9:16 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity
Replies: 1
Views: 39

Re: Heat capacity

Hi Madelyn!

Using just heat capacity would apply to a system like a calorimeter. Using specific capacity would apply to specific substances or elements.

Hope that helps!
by MaanasO 1A
Fri Feb 08, 2019 9:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction Enthalpies
Replies: 2
Views: 62

Re: Reaction Enthalpies

Hi Kristen! There are three different ways to calculate the enthalpy of the reaction. One is breaking down the reaction into steps (those steps will be given to you) and altering the heat output of each step based on scalar multiplication and flipping the reaction and then summing them up. The secon...
by MaanasO 1A
Fri Feb 08, 2019 9:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies
Replies: 1
Views: 54

Re: Standard Enthalpies

Nah I think all the enthalpies we need will be given to us. The only ones you have to know are the elements in their natural state (which is 0). So things likes O2(g), N2(g), C(s), etc all have standard enthalpies of formation of 0 J.

Hope that helps!
by MaanasO 1A
Sat Feb 02, 2019 11:31 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Self-test 4A.1A
Replies: 1
Views: 36

Re: Self-test 4A.1A

Hey Phillip! I've done the work (hehe) on my own and I get the same answer as you. I don't it's possible to do the reversible expansion formula since that applies to gases, and your units look accurate. Have you checked the errors in the soln manual on the class website? Maybe there's something in t...
by MaanasO 1A
Sat Feb 02, 2019 11:09 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Final Temperature at Constant Pressure, and then at Constant Volume
Replies: 2
Views: 107

Re: Final Temperature at Constant Pressure, and then at Constant Volume

Hi Mariah! I'm assuming that you mean T = 298 K and not V = 298 L. As such, the volume won't be constant, but the pressure will be. So I don't think you need to worry about there being a constant volume since we don't know if the gas does any work. We know that no work is done ON the gas, but by add...
by MaanasO 1A
Sat Feb 02, 2019 11:05 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy
Replies: 3
Views: 114

Re: Internal Energy

Hi Ashley!

This equation relates to the kinetic energy of gas molecules. The derivation is mathematically rigorous, but you can check out the derivation here: http://hyperphysics.phy-astr.gsu.edu/hb ... ke.html#c1

Hope that helps!
by MaanasO 1A
Thu Jan 24, 2019 4:56 pm
Forum: Phase Changes & Related Calculations
Topic: ΔH and ΔU
Replies: 2
Views: 58

Re: ΔH and ΔU

U refers to the potential energy of the system, and enthalpy (H) is one of the components that contributes to the overall U of a system.
by MaanasO 1A
Thu Jan 24, 2019 4:55 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible and Irreversible Process
Replies: 3
Views: 67

Re: Reversible and Irreversible Process

A reversible chemical reaction will be noted with two arrows and will have an equilibrium constant. Reactions that proceed completely from reactants to products are denoted with a one-way arrow and do not have equilibrium constants.
by MaanasO 1A
Thu Jan 24, 2019 9:21 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: predict solubility
Replies: 2
Views: 60

Re: predict solubility

I don't think you actually can use the equilibrium constant to predict solubility. They are related but they don't depend on each other I think.
by MaanasO 1A
Fri Jan 18, 2019 7:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Understanding Q
Replies: 9
Views: 137

Re: Understanding Q

Hi Cecilia!

So Q and K are calculated in the same way but with different concentrations. Think of K as the Q when the reaction is at equilibrium.

Hope that helps!
by MaanasO 1A
Thu Jan 17, 2019 5:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How Ka and Kb relate to each other
Replies: 1
Views: 38

Re: How Ka and Kb relate to each other

Hi Maayan! In the cases of Ka and Kb, we only deal with dissolving the acid or base in question in water. And the Ka and Kb aren't representative of opposite directions of the same reaction. Let's take NH3 (a weak base). The Kb for NH3 deals w/ the reaction that forms NH4+ and OH-. Ka for NH4+ deals...
by MaanasO 1A
Wed Jan 16, 2019 10:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Endothermic Reaction
Replies: 4
Views: 77

Re: Endothermic Reaction

Hi Emma!

So I'm assuming you mean just K when you mention Kw. Since endothermic reactions require heat, adding heat will shift the reaction to the products. K will change because thermodynamics (we'll learn this later).

Hope that helps!
by MaanasO 1A
Sun Jan 13, 2019 9:31 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in Partial Pressure
Replies: 5
Views: 101

Changes in Partial Pressure

Whenever we come across a problem that asks for the change in the system when the partial pressure of a gas changed, do we assume that the volume/concentration has changed and that temp is konstant?
by MaanasO 1A
Thu Jan 10, 2019 11:24 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Finding K in 5I.7
Replies: 3
Views: 61

Re: Finding K in 5I.7

No we're not supposed to know that stuff (yet). G refers to Gibbs Free Energy, and that's a central term in thermodynamics. We'll probably go over that later on in the quarter, but for now, we don't need to know it.
by MaanasO 1A
Thu Jan 10, 2019 11:23 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature Affecting K
Replies: 2
Views: 52

Re: Temperature Affecting K

Hello Stevin!

If the temperature increases, then more energy is provided. If the reaction is endothermic, then a higher temperature will support the forward reaction and shift the equilibrium to the right. If the reaction is exothermic, then the opposite will happen.

Hope that helps!
by MaanasO 1A
Tue Jan 08, 2019 5:03 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 11.13c (6th Edition)
Replies: 2
Views: 56

Re: 11.13c (6th Edition)

Hello Rimsha!

Yes your expression for the equilibrium constant looks accurate!
by MaanasO 1A
Tue Dec 04, 2018 5:14 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Dilution
Replies: 1
Views: 38

Re: Dilution

So you're simply using the dilution formula, where [H3O+] is the initial concentration, Vi is the initial volume, Vf is the final volume, and Cf is the final concentration.

[H3O+]Vi = CfVf => [H3O+]Vi/Vf = Cf

You then use the final concentration of H3O+ to figure out the pH.

Hope that helps!
by MaanasO 1A
Tue Dec 04, 2018 5:11 pm
Forum: General Science Questions
Topic: naming coordination compounds
Replies: 2
Views: 116

Re: naming coordination compounds

The order doesn't matter among the ligands themselves. They all just need to come before the metal cation in the naming and after in the chemical formula.
by MaanasO 1A
Tue Dec 04, 2018 5:10 pm
Forum: Naming
Topic: writing formulas
Replies: 2
Views: 29

Re: writing formulas

The order of the ligands in the coordination compound doesn't really matter; they just need to come after the metal they're all surrounding.
by MaanasO 1A
Tue Dec 04, 2018 5:02 pm
Forum: General Science Questions
Topic: aqua
Replies: 1
Views: 80

Re: aqua

It's the same either way. OH2 just specifies that the Oxygen atom in the water molecule is the one donated the electron pair to the coordination compound. The di just comes from the outer subscript.
by MaanasO 1A
Tue Nov 27, 2018 5:19 pm
Forum: Dipole Moments
Topic: Size and IM interactions
Replies: 2
Views: 48

Re: Size and IM interactions

This is in reference to London Dispersion Forces (Induced-dipole-induced dipole or LDF). So molar mass and size aren't actually the reason why LDF strength increases. It's directly related to the number of electrons present. However, usually heavier molecules/atoms have more electrons, making them m...
by MaanasO 1A
Tue Nov 27, 2018 5:15 pm
Forum: Hybridization
Topic: Regions of Electron Desnity
Replies: 5
Views: 89

Re: Regions of Electron Desnity

Yes! When determining hybridization, you have to count the number of lone pairs and sigma bonds around the atom of interest.
by MaanasO 1A
Tue Nov 27, 2018 5:14 pm
Forum: Bond Lengths & Energies
Topic: SO2 and SO3 bond length
Replies: 2
Views: 734

Re: SO2 and SO3 bond length

Hi Isabel!

The bond lengths actually won't change based on the electron lone pairs. The bond ANGLES, however, will be slightly different due to the repulsion of lone pair electrons.

Hope that helps!
by MaanasO 1A
Tue Nov 27, 2018 5:13 pm
Forum: Electronegativity
Topic: Electronegativity values
Replies: 2
Views: 225

Re: Electronegativity values

Dr. Lavelle mentioned that we won't have to know the specific electronegativity values, but if for some reason we did, he'd give us the values.
by MaanasO 1A
Tue Nov 27, 2018 5:11 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: dipole-dipole and dipole-induced dipole
Replies: 2
Views: 67

Re: dipole-dipole and dipole-induced dipole

Hi Ashley! Short answer: Dipole-dipole involves 2 polar molecules, and dipole-induced dipole involves a polar and a nonpolar molecule. Dipole-dipole interactions take place between 2 molecules with net dipoles. These molecules don't even need to be the same. So SO2 is polar (because of its bent shap...
by MaanasO 1A
Wed Nov 21, 2018 8:00 am
Forum: Hybridization
Topic: hybridization with bonds
Replies: 2
Views: 54

Re: hybridization with bonds

If there is a single bond, it's always a sigma bond. If there are multiple bonds, one will be a sigma bond, and the remaining ones will be pi bonds. If you have a triple bond, then one will be a sigma bond and the other two will be pi bonds.
by MaanasO 1A
Wed Nov 21, 2018 7:57 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Organizing atoms around central atom
Replies: 1
Views: 24

Re: Organizing atoms around central atom

The O and Cl atoms can be arranged in any way around the S atom. It won't make a difference because it'll still maintain the same stability.
by MaanasO 1A
Wed Nov 21, 2018 7:56 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 5
Views: 85

Re: Molecular Shape

I think it would be better to understand how the shapes correspond to different AXE forms rather than simply memorize them. Some are nice, like trigonal planar. You know that if you have 3 regions of electron density around the central atom, then they all need to be equally spaced from each other (3...
by MaanasO 1A
Tue Nov 13, 2018 8:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecules with the same molecular formula
Replies: 1
Views: 33

Re: Molecules with the same molecular formula

Hi Ian! I believe this is more applicable to the realm of organic chemistry, but I think you can figure it out based on the way the formula is written. There are a bunch of naming conventions for these sorts of molecules. The link below has more information about this. http://www.chem.uiuc.edu/GenCh...
by MaanasO 1A
Tue Nov 13, 2018 8:47 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: dipole dipole and london forces
Replies: 2
Views: 57

Re: dipole dipole and london forces

Hi Lorena!

London forces exist in all molecules/compounds. Dipole-dipole interactions only occur among polar molecules.

Hope that helps!
by MaanasO 1A
Tue Nov 13, 2018 8:45 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 3
Views: 86

Re: Lewis Structure

Hi Rachel! Yes, the compound in question could theoretically have a triple bond between C and Cl and a single bond between C and N. The Cl atom would have 1 lone pair (giving it a formal charge of 7-(2+3) = +2) and the N atom would have 3 lone pairs (giving it a formal charge of 5 - (6+1) = -2). The...
by MaanasO 1A
Sat Nov 10, 2018 4:57 pm
Forum: Trends in The Periodic Table
Topic: Atomic radius
Replies: 3
Views: 199

Re: Atomic radius

As you go the right across a period, more protons are added to the nucleus => the nucleus has a greater positive charge => it has a tighter pull on the electrons. Down a group however, because the quantum number n increases, the electrons are significantly further away, which causes the atomic radiu...
by MaanasO 1A
Sat Nov 10, 2018 4:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test
Replies: 2
Views: 57

Re: Test

It's after Thanksgiving, so no need to worry about weird timings.
by MaanasO 1A
Sat Nov 10, 2018 4:54 pm
Forum: Lewis Structures
Topic: 6th edition ch3 3.103
Replies: 1
Views: 89

Re: 6th edition ch3 3.103

Hey Jeremiah! A) Just make sure that the carbon atoms have SINGLE bonds to the oxygen, giving each O atom 3 lone pairs and 1 bonding pair. The C-C bonds alternate double and single around the chain, and the H atoms are added to those C atoms that need the full octet. B) The oxygen atoms each will ha...
by MaanasO 1A
Sat Nov 10, 2018 4:35 pm
Forum: Electronegativity
Topic: Electron Affinity
Replies: 3
Views: 115

Re: Electron Affinity

The K+ ion would more likely to have the higher electron affinity value. The ion has a full valence shell, so a lot more energy would be required to break that stable state that it would be to add another electron to a neutral K ion (which then would have a filled 4s orbital).
by MaanasO 1A
Tue Oct 30, 2018 4:16 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 14
Views: 353

Re: Drawing Lewis Structures

Hi Saachi! So Lewis diagrams are based on how many atoms are bonded to a certain atom. CH4 has 4 hydrogen atoms bonded to the same carbon atom, so they'll look like a plus sign. We haven't done VSEPR models, so these diagrams don't actually represent how the molecule looks; they're just drawn that w...
by MaanasO 1A
Tue Oct 30, 2018 4:13 pm
Forum: Octet Exceptions
Topic: Expanded Octet Circumstances
Replies: 1
Views: 113

Re: Expanded Octet Circumstances

Hi Jasmine! Anything that's period 3 and down can have expanded octets. Every element with n >= 3 can store electrons in the d subshell (and if n >= 4, this applies to the f subshell as well), so sulfur can conceivably store more than just 8. The circumstances just depend on the polyatomic ion/molec...
by MaanasO 1A
Tue Oct 30, 2018 4:09 pm
Forum: Quantum Numbers and The H-Atom
Topic: degeneracy
Replies: 2
Views: 134

Re: degeneracy

Hi! So degeneracy refers to the same energy level, BUT this is not the same as the principal quantum number N. Remember Prof Lavelle's drawing of the orbitals in lecture? He drew 1s, then a line for 2s, and then 3 lines for 2p. All of the orbitals in the same subshell (s, p, d, f) are expected to ha...
by MaanasO 1A
Tue Oct 30, 2018 4:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d and 4s: filling and energy
Replies: 1
Views: 84

Re: 3d and 4s: filling and energy

Hi Jasmine! So apparently the reasons are extremely complicated, but once we cross Calcium, because the # of protons in the nucleus changes, the 3d state requires slightly less energy than the 4s state. The 4s electrons have greater penetrating power (this means that the electrons can be found right...
by MaanasO 1A
Wed Oct 24, 2018 1:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Quantum Number L
Replies: 3
Views: 82

Re: Quantum Number L

Hi Phoebe! Yes so for any n, L will range from 0 to (n-1). So if n = 5, then L can be 0, 1, 2, 3, 4. Also, L doesn't determine the orbital shape necessarily. The quantum number n gives you the energy level. Each energy level will contain certain subshells (these are s, p, d, and f). We are doing a s...
by MaanasO 1A
Wed Oct 24, 2018 1:46 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 2
Views: 49

Re: Electron Affinity

Hi Jerome!

They are similar. Electronegativity refers to how well an atom can attract an electron. Electron affinity is the actual amount of energy released when an atom gains an electron. They are similar ideas, but they aren't the exact same thing.

Hope that helps!
by MaanasO 1A
Wed Oct 24, 2018 1:43 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shielding effect
Replies: 6
Views: 221

Re: Shielding effect

Hi Deepika! Shielding refers to the electron-electron repulsion forces that counter the attractive forces between the nucleus and the individual electrons. When you have electrons that are closer to the nucleus on average, they provide repulsion forces that greatly reduce the effective nuclear charg...
by MaanasO 1A
Tue Oct 23, 2018 5:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Number
Replies: 5
Views: 178

Re: Magnetic Quantum Number

Hi Sarah!

I believe we don't need to understand how each of the orbitals line up with the axes. S-orbitals are spheres, but d and f orbitals are very much complicated and are beyond the scope of our class.

Hope that helps!
by MaanasO 1A
Mon Oct 15, 2018 6:36 pm
Forum: Properties of Electrons
Topic: Photon Momentum
Replies: 1
Views: 80

Re: Photon Momentum

Hi Courtney! This is a question with a rather weird answer. Photons have mass... technically. If you remember from lecture, Professor Lavelle used a term: "rest mass." This is mass in the traditional sense, the way we're used to thinking about it. Photons do not have a rest mass, but they ...
by MaanasO 1A
Mon Oct 15, 2018 6:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Quantum Number L
Replies: 3
Views: 82

Re: Quantum Number L

Hi Phoebe! L is not actually (n-1). The quantum number is given by 0 <= l <= (n-1). The range of L tells you how many subshells, or different types of orbitals, can be found within a given shell. Let's take n = 2. This corresponds to the 2nd period on the Period Table (Lithium to Neon). If n = 2, th...
by MaanasO 1A
Mon Oct 15, 2018 6:12 pm
Forum: DeBroglie Equation
Topic: Electrons as Waves
Replies: 1
Views: 54

Re: Electrons as Waves

Hi Max! The short answer: Yes (more or less). The long answer: What we saw in lecture was a 2-D representation of what the wave looks like. In the 3-D, the presence of two electrons would result in some electron-electron repulsion that may cause a difference in momentum, since negative charges exert...
by MaanasO 1A
Sat Oct 13, 2018 12:58 pm
Forum: *Shrodinger Equation
Topic: Shrodinger Equation Meaning
Replies: 3
Views: 134

Re: Shrodinger Equation Meaning

Hi Hannah! So Schrodinger's Equation is applicable to any individual electron. It's insanely complicated, involving fancy linear algebra and multivariable calculus concepts, but the basic idea is that it helps you understand where an electron is likely to be relative to a nucleus. The solution for S...
by MaanasO 1A
Sat Oct 13, 2018 12:51 pm
Forum: DeBroglie Equation
Topic: DeBroglie Wavelength
Replies: 1
Views: 68

Re: DeBroglie Wavelength

Hi Divya! de Broglie's wavelength formula was designed to be a generalized extension of Einstein's Wave-Particle Duality of Light. When this formula is applied to particles with small masses, we can see that its relatively significant values show that small particles have large wavelengths relative ...
by MaanasO 1A
Sat Oct 13, 2018 12:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1.25
Replies: 1
Views: 95

Re: 1.25

Hi Adrian! So for this question, we want to use Heisenberg's Uncertainty equation. We know that the equation is (dx)(dp) >= h/(4pi), where dx is uncertainty in position and dp is uncertainty in momentum. p = mv. So it stands to reason to say dp = d(mv). HOWEVER, we know the position of a hydrogen at...
by MaanasO 1A
Tue Oct 09, 2018 9:09 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity
Replies: 4
Views: 325

Re: Molarity

Hi! For the molar mass of KMnO4, I got (39.10) + (54.94) + 16.00(4) = 158.0 g/mol. This means the moles of KMnO4 is 5.00/158.0 = 0.0316 moles. The concentration of this initial solution is 0.0316/.150 = 0.211 M. MiVi = MfVf => Mf = MiVi/Vf = (0.211)*(0.150)/0.250 = 0.127 M. This is final concentrati...
by MaanasO 1A
Tue Oct 09, 2018 9:03 pm
Forum: Administrative Questions and Class Announcements
Topic: 7 Questions Handin Date
Replies: 2
Views: 140

Re: 7 Questions Handin Date

We turn them in during discussions from this week onwards. I had discussion this afternoon, and we turned in our homework after the exam.
by MaanasO 1A
Tue Oct 09, 2018 9:02 pm
Forum: Molarity, Solutions, Dilutions
Topic: Problem G25
Replies: 2
Views: 275

Re: Problem G25

Hi Alex! This problem is an interesting one. We start with 10 mL of 0.10 M solution. But we double the volume 90 times. The volumes changes from 10 -> 20 -> 40 -> 80 ->... so on and so forth. The math for this turns out to be: 10 mL -> 0.01L * 0.10 M = 0.001 moles The volume is 0.01 L * 2^90 (becaus...
by MaanasO 1A
Tue Oct 09, 2018 8:56 pm
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 2
Views: 33

Re: Photoelectric Effect

Hi! From what I understand, the photoelectric effect wasn't tested through an experiment to prove its existence. A group of scientists attempted to observe incandescence, the phenomenon of an object glowing when it's really hot. Because classical physics could not yield equations that could explain ...
by MaanasO 1A
Wed Oct 03, 2018 7:51 pm
Forum: SI Units, Unit Conversions
Topic: HW Question E1, when do we convert units?
Replies: 1
Views: 89

Re: HW Question E1, when do we convert units?

Hi! So in this question, it doesn't explicitly say what unit of distance was expected. SI says distance is in meters, so that would be your safest bet if the units weren't specified. I suppose km makes more sense because it's such a large distance, but I don't think your answer's wrong. As long as y...
by MaanasO 1A
Wed Oct 03, 2018 6:54 pm
Forum: Limiting Reactant Calculations
Topic: Limiting reactants product of moles
Replies: 4
Views: 104

Re: Limiting reactants product of moles

Hi Ames! So the molar mass of calcium carbonate (CaCO3) is 100.0869 g/mol. Multiplying 1 kg by 1000 gives you 1000g of CaCO3. Converting from mass to moles means 1000 g CaCO3 * 1 mol CaCO3/100.1 g CaCO3 = 10 mol CaCO3. To answer this question, we can assume that CaCO3 is the limiting reactant and we...
by MaanasO 1A
Wed Oct 03, 2018 6:32 pm
Forum: Limiting Reactant Calculations
Topic: This question from the post assessment
Replies: 2
Views: 118

Re: This question from the post assessment

So Andre's answer is correct, in theory. To your question, Ames, no, 14 g of product cannot be formed. HOWEVER, 12 g of product will not always be formed in the reaction. Firstly, the reactants may or may not completely react with one other (limiting reactants). Secondly, because of side reactions a...
by MaanasO 1A
Fri Sep 28, 2018 6:45 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Visualizing Orbitals in Atoms
Replies: 3
Views: 112

Re: Visualizing Orbitals in Atoms

Hi Ashley! So from my understanding of orbitals, they represent the probable region of locations an electron can be found at a given time. Electrons with lower energies move a smaller distance away from the nucleus. So as the energy increases, the size of the orbital as well, since the electron has ...

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