Search found 80 matches

by chemboi
Mon Feb 17, 2020 10:08 pm
Forum: Balancing Redox Reactions
Topic: Same Molecule as Both Reducing and Oxidizing Agent
Replies: 1
Views: 23

Re: Same Molecule as Both Reducing and Oxidizing Agent

I recommend reading over "disproportionatoin reactions" from here: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Redox_Chemistry/Oxidation_State/Oxidation_States_II I don't know why this occurs, but it does :/ I th...
by chemboi
Mon Feb 17, 2020 9:58 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Exothermic rxns being spontaneous
Replies: 5
Views: 19

Re: Exothermic rxns being spontaneous

Spontaneity is determined by the sign of G, where G = H - T*S. For exothermic reactions., H is negative, so it is more common for G to be negative as well (S is positive, or negative T*S term is lower in absolute value than H)
by chemboi
Mon Feb 17, 2020 9:31 pm
Forum: Balancing Redox Reactions
Topic: 6K.1
Replies: 1
Views: 13

Re: 6K.1

Your final equation is balanced, and I really like how you did each step, made it easy to follow :) The e- are indeed on the correct side, because this is a reduction half reaction, not oxidation. Cr is 6+ in Cr2O7(2-) and ends up as 3+, so it has gained electrons and its oxidation number has... red...
by chemboi
Sun Feb 16, 2020 10:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Acids/Bases in non-neutral solutions
Replies: 2
Views: 8

Re: Acids/Bases in non-neutral solutions

To clarify the good previous response, make sure you have for your final division operation's numerator: [H+] minus the initial conc. from starting pH conditions
Using [H+] alone would overestimate the dissociation of the acid.
by chemboi
Sun Feb 16, 2020 10:20 pm
Forum: Balancing Redox Reactions
Topic: Oxygen and Hydrogen
Replies: 4
Views: 15

Re: Oxygen and Hydrogen

For hydrogen, it depends on what kind of atom the hydrogen is bonded to, could make the charge of H 1+ or 1-
Oxygen has lots of exception situations such as in peroxides.
by chemboi
Sun Feb 16, 2020 10:17 pm
Forum: Balancing Redox Reactions
Topic: easier to split?
Replies: 6
Views: 23

Re: easier to split?

To add on to previous responses, if you're given an unbalanced (stiochiometrically and unbalanced charge) starting equation, it's much easier to balance the half reactions individually than the net reaction right off the bat.
by chemboi
Sun Feb 16, 2020 10:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated Systems.
Replies: 5
Views: 15

Re: Isolated Systems.

Delta S should remain zero I think. W depends on what you've got in your system :) unless you've got atoms at abs. zero, W is likely >0
by chemboi
Sun Feb 16, 2020 10:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Curve
Replies: 45
Views: 246

Re: Midterm Curve

Individual tests aren't curved but the class grade distribution will be at the end of the quarter if the pre-curve average falls short of what he wants for the final average.
by chemboi
Thu Feb 06, 2020 5:23 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Enthalpy versus heat
Replies: 11
Views: 43

Re: Enthalpy versus heat

I think they equal each other when there is no work being done on the system. Enthalpy is the change in heat of a system at constant pressure, and yes it is a state function vs. heat which depends on the path of the reaction.
by chemboi
Thu Feb 06, 2020 5:18 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Changes
Replies: 2
Views: 7

Re: Entropy Changes

Whichever factor allows for more "free movement" of the atoms entails more entropy, because the atoms can exist in more states.
by chemboi
Thu Feb 06, 2020 5:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Energy Change
Replies: 4
Views: 16

Re: Energy Change

if its negative, it is spontaneous (will proceed forward as written)
by chemboi
Wed Feb 05, 2020 11:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: heat capacity at constant V and constant P
Replies: 2
Views: 17

Re: heat capacity at constant V and constant P

at constant volume, q = delta U because no work is being done in expansion, so w is zero. q+w = delta U, so only q is left over. If someone could clarify the second part, that would be great because I'm not sure :(
by chemboi
Wed Feb 05, 2020 11:23 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Heat capacity
Replies: 4
Views: 20

Re: Heat capacity

These values, especially for gases, are likely to be given. However, the previous poster makes a good point that we could be expected to derive them for a given situation if other appropriate values are known. Could show up as more of a conceptual type question.
by chemboi
Wed Feb 05, 2020 11:22 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv
Replies: 4
Views: 22

Re: Cp and Cv

The subscript describes the conditions: Cp is for constant pressure, Cv is for constant volume.
by chemboi
Wed Feb 05, 2020 11:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.9
Replies: 3
Views: 40

Re: 4D.9

The 4 in front of the TNT molecule in the given equation indicates this.
by chemboi
Wed Feb 05, 2020 11:19 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 7
Views: 61

Re: Midterm

To expand on the previous response, Dr. Lavelle seems to be devoting lots of time to showing the related nature of the equations during the derivation process. This seems like prime material for a conceptual type question, so it may be prudent to understand the relation of the equations.
by chemboi
Wed Feb 05, 2020 11:18 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Decreasing, Temperature Increasing
Replies: 6
Views: 25

Re: Entropy Decreasing, Temperature Increasing

This ties in with the formula deltaS = (q reversible) / T , so with higher T the change in S is reduced.
by chemboi
Wed Feb 05, 2020 11:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4.33
Replies: 1
Views: 7

Re: 4.33

Typically if combustion enthalpies are given, it implies using the product-reactant sum formula.
by chemboi
Wed Feb 05, 2020 11:16 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv
Replies: 10
Views: 37

Re: Cp and Cv

We won't be expected to have these memorized. Perhaps only for water would it be expected that we know, but that's not a gas. So for your question, no :)
by chemboi
Wed Feb 05, 2020 11:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Potential Midterm Questions
Replies: 2
Views: 16

Re: Potential Midterm Questions

Perhaps knowing the structures is advantageous for knowing how many of which bond types are broken. It seems in relevant problems that the molecules are given in an expanded format, which implies the relevant bonds.
by chemboi
Sat Feb 01, 2020 8:25 pm
Forum: Calculating Work of Expansion
Topic: thermodynamic equations
Replies: 3
Views: 30

Re: thermodynamic equations

One important one to remember is that the w = -P(deltaV) equation only applies for constant external pressure situations.
by chemboi
Sat Feb 01, 2020 8:24 pm
Forum: Calculating Work of Expansion
Topic: integral
Replies: 3
Views: 20

Re: integral

integrals may be used for reversible changes of volume in a gas producing reaction. when you integrate from v1 to v2 of an external pressure, you get P*deltaV
by chemboi
Sat Feb 01, 2020 8:20 pm
Forum: Calculating Work of Expansion
Topic: 4A.3 (HW)
Replies: 2
Views: 37

Re: 4A.3 (HW)

for work, use w = -P(deltaV). Make sure to keep track of units: converting atm to pascals, and converting cm to meters, will give pascals*meters&3 which is joules. change in internal energy is w if no heat transfer occurs.
by chemboi
Sat Feb 01, 2020 8:18 pm
Forum: Calculating Work of Expansion
Topic: 4A.3
Replies: 2
Views: 30

Re: 4A.3

The basis of the question gets to the heart of w = -P deltaV, so I would think it's fair game.
by chemboi
Mon Jan 27, 2020 5:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Steam graph
Replies: 5
Views: 15

Re: Steam graph

While another poster may want to break it down super in depth, I think throughout interpretation of explanations you should keep in mind the differences between the heat energy of the water and its temperature. For steam, increasing temperature requires imparting more heat.
by chemboi
Thu Jan 23, 2020 3:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6 C.21 part b
Replies: 1
Views: 20

Re: 6 C.21 part b

I thought that the reasoning for formic acid being slightly weaker is the CH3 group in acetic acid does have that inductive behavior, but to the effect of donating electrons and decreasing the polarization of the total molecule.
by chemboi
Wed Jan 15, 2020 4:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sig Figs on HW 5H.1c
Replies: 4
Views: 22

Re: Sig Figs on HW 5H.1c

The given value of K = 41 has only 2 sig figs, so by the sig fig rules your answer must only have 2.
by chemboi
Wed Jan 15, 2020 4:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Significant figures for acid and base calculations
Replies: 3
Views: 16

Re: Significant figures for acid and base calculations

Preserve decimal points during intermediate steps, and only cut off decimals as part of adhering to sig fig rules for your final answer.
by chemboi
Fri Dec 06, 2019 5:30 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6D.11 part e and f
Replies: 1
Views: 17

Re: 6D.11 part e and f

Here, Cl- and NO3- anions are the conjugate bases of strong acids. Thus, they act as exceptionally weak bases in solution, and can be considered practically neutral ions in solution. Any change in pH will not come from these anions, but may come from the metal cations. We see that Al3+ and Cu2+ are ...
by chemboi
Fri Dec 06, 2019 5:27 pm
Forum: Naming
Topic: cyano v. cyanido
Replies: 4
Views: 34

Re: cyano v. cyanido

Both are valid, cyanido is in correspondence with new IUPAC naming conventions. Textbook uses this new convention, but in lecture Dr. Lavelle has used the old system. I guess whichever you choose to use, stay consistent with it.
by chemboi
Wed Dec 04, 2019 1:43 am
Forum: Lewis Acids & Bases
Topic: Examples of acids
Replies: 1
Views: 15

Re: Examples of acids

Depends on the strengths of the contributing acid, in this case citric vs. acetic acid.
by chemboi
Wed Dec 04, 2019 1:41 am
Forum: General Science Questions
Topic: Aqueous
Replies: 3
Views: 63

Re: Aqueous

Some molecules like HCl remain "intact" in other states liek gas phase, but in water (aqueous), they dissociate. It's an important distinction to keep track of.
by chemboi
Wed Dec 04, 2019 1:40 am
Forum: Hybridization
Topic: hybridization of lone pairs
Replies: 2
Views: 17

Re: hybridization of lone pairs

I believe that the hybridization of any region of electron density around the central atom can be described in terms of the central atom's hybridization. Oxygen is sp3 hybridized, so all bonds and lone pairs are also sp3 (lone pairs count as a region of electron density).
by chemboi
Wed Dec 04, 2019 1:36 am
Forum: Hybridization
Topic: hybridization
Replies: 3
Views: 24

Re: hybridization

I believe that electron promotion is not necessary for hybridization. For example, it does not occur in NH3, which has hybridization.
by chemboi
Wed Dec 04, 2019 1:35 am
Forum: Determining Molecular Shape (VSEPR)
Topic: vsepr formula
Replies: 7
Views: 50

Re: vsepr formula

My interpretation is the AXnEm form of central atom, # surrounding atoms, and # lone pairs. If anyone else knows for sure, that would be greatly appreciated!
by chemboi
Wed Dec 04, 2019 1:33 am
Forum: Naming
Topic: Oxidation numbers and charge
Replies: 1
Views: 20

Re: Oxidation numbers and charge

I found this resource (and teh associated part 2 page) very helpful for oxidation states: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Redox_Chemistry/Oxidation_State Knowing oxidation states lets you figure out the net cha...
by chemboi
Wed Dec 04, 2019 1:32 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate ligands
Replies: 1
Views: 21

Re: Polydentate ligands

If atoms with the lone pairs are separated by two "spacer" atoms and can rotate, or are in the same plane, then that is a configuration conducive to polydentate behavior.
by chemboi
Tue Dec 03, 2019 2:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Final
Replies: 2
Views: 28

Re: Final

I think that the extent of naming we have covered would be sufficient to justify a question that asks us to write out the formula of a compound such as EDTA given the expanded name.
by chemboi
Tue Dec 03, 2019 2:28 pm
Forum: Polyprotic Acids & Bases
Topic: box 6E.1
Replies: 1
Views: 22

Re: box 6E.1

I don't think the method to calculate such values has been covered explicitly so far in lecture
by chemboi
Sun Nov 17, 2019 4:34 pm
Forum: Electronegativity
Topic: determining electronegativity
Replies: 4
Views: 35

Re: determining electronegativity

I don't think we have learned how to calculate actual values. We should know relative values, however.
by chemboi
Sun Nov 17, 2019 4:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal planar vs trigonal pyramidal
Replies: 3
Views: 18

Re: trigonal planar vs trigonal pyramidal

The lewis structures should not look the same. trigonal planar lewis structure will have a central atom with 3 regions of electron density, whereas trigonal pyramidal has 4 regions: 3 bonds and 1 lone pair
by chemboi
Sun Nov 17, 2019 4:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook question 2.63
Replies: 1
Views: 13

Re: Textbook question 2.63

The nitrogen is sp2 hybridized, with trigonal planar geometry which has bond angles of 120 degrees.
by chemboi
Sun Nov 17, 2019 4:27 pm
Forum: Ionic & Covalent Bonds
Topic: Hydrogen Bonds
Replies: 6
Views: 30

Re: Hydrogen Bonds

NOF bound to H
by chemboi
Sun Nov 17, 2019 4:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Bond Angles?
Replies: 3
Views: 22

Re: Determining Bond Angles?

Bond angles of certain configurations you must memorize, ie 90, 120, 109.5 and as lone pairs come into play, you should be able to reason that the electron repulsion from the lone pairs would cause the bond angles to decrease slightly relative to their normal angle.
by chemboi
Sun Nov 17, 2019 4:24 pm
Forum: Sigma & Pi Bonds
Topic: Sigma V Pi
Replies: 5
Views: 35

Re: Sigma V Pi

I found this website very helpful in pointing out their differences: https://www.majordifferences.com/2014/1 ... -bond.html
by chemboi
Sun Nov 17, 2019 4:23 pm
Forum: Sigma & Pi Bonds
Topic: explanation
Replies: 2
Views: 21

Re: explanation

by chemboi
Sun Nov 17, 2019 4:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XeF2
Replies: 5
Views: 43

Re: XeF2

XeF2 is nonpolar. The three lone pairs are in the equatorial plane, while the two F form the :poles" at 180 degrees from each other.
by chemboi
Sun Nov 17, 2019 4:21 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 10
Views: 65

Re: Bond Length

They are experimentally determined.
by chemboi
Fri Nov 15, 2019 4:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR and Lewis Structures
Replies: 2
Views: 17

Re: VSEPR and Lewis Structures

To elaborate on the previous response, a valid lewis structure for NH3 would have the 3 H drawn perpendicularly to eachother.
by chemboi
Fri Nov 15, 2019 4:31 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-induced dipole bond
Replies: 5
Views: 24

Re: Dipole-induced dipole bond

That follows the general convention of cutoffs of 0.4 and 1.7 electronegativity differences to determine if a bond is nonpolar (0-0.4), polar (0.4-1.7), or ionic (1.7+)
by chemboi
Fri Nov 15, 2019 4:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: How to tell polar or non polar from lewis structure?
Replies: 9
Views: 61

Re: How to tell polar or non polar from lewis structure?

Presence of asymmetric lone pairs, and asymmetric distribution of atoms with electronegativity differences are indicators of polarity
by chemboi
Thu Nov 07, 2019 4:38 pm
Forum: Lewis Structures
Topic: 12 in Dino nuggets
Replies: 2
Views: 36

Re: 12 in Dino nuggets

Also keep in mind which atoms must obey the octet rule, and which can support an expanded octet. These considerations will help guide you to a valid structure.
by chemboi
Thu Nov 07, 2019 4:35 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 4
Views: 24

Re: Lewis Structure

To elaborate on step 2, the central atoms is usually the one with the lowest ionization energy. Additionally, keep in mind situations in which an expanded octet is valid.
by chemboi
Thu Nov 07, 2019 4:34 pm
Forum: Lewis Structures
Topic: Lewis structure
Replies: 5
Views: 32

Re: Lewis structure

What is the reasoning behind only having one double bond, instead of two or three?
by chemboi
Thu Nov 07, 2019 4:26 pm
Forum: Ionic & Covalent Bonds
Topic: Solubility
Replies: 3
Views: 25

Re: Solubility

To clarify the previous response, many covalent compounds are polar. For example, H2O and NH3 possess covalent bonds but are polar and thus soluble in water.
by chemboi
Thu Nov 07, 2019 4:24 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent character and ionic character
Replies: 5
Views: 28

Re: Covalent character and ionic character

To expand on the first response, we refer to bonds as being on a spectrum between covalent and ionic character because a given bond may not be perfectly covalent nor ionic; while a bond with an electronegativity difference of 0.1 has high covalent character, it nonetheless is not a perfectly equal s...
by chemboi
Thu Nov 07, 2019 4:18 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: Comparing forces of attraction
Replies: 4
Views: 22

Re: Comparing forces of attraction

To elaborate on the previous answer, it is useful and clear to think of the strengths of dipoles as proportional to the electronegativity differences of involved atoms.
by chemboi
Thu Nov 07, 2019 4:16 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: Instantaneous dipole moment
Replies: 5
Views: 36

Re: Instantaneous dipole moment

In my searching I haven't found much more than a description of the duration as "an instant". Probably an arbitrarily brief moment of time that does not bear relevance for topics covered in this class.
by chemboi
Tue Nov 05, 2019 12:29 am
Forum: Lewis Structures
Topic: Valence Electrons in D Subshell
Replies: 5
Views: 36

Re: Valence Electrons in D Subshell

As this (https://www.quora.com/Why-does-titanium-have-4-valence-electrons-if-it-is-in-group-3) answer to a similar question explains, even though the 3d electrons are not in the n=4 level, their energy is so close to that of the 4s electrons that all are considered valence electrons that can partici...
by chemboi
Tue Nov 05, 2019 12:27 am
Forum: Lewis Structures
Topic: Valence Electrons in D Subshell
Replies: 5
Views: 36

Re: Valence Electrons in D Subshell

Valence electrons includes all e- not part of the "noble gas core", so you count the 5 ei in the d state in addition to the 2 e- in the s state.
by chemboi
Tue Nov 05, 2019 12:24 am
Forum: Properties of Electrons
Topic: Ionization energy
Replies: 3
Views: 44

Re: Ionization energy

So far it seems that questions deal with first ionization energy. Perhaps it is good to keep in mind that the second IE will always be greater than the first. Also, the difference between 1st IE and second IE may be drastically different between elements: the difference is much more pronounced in Al...
by chemboi
Mon Oct 28, 2019 12:29 am
Forum: Photoelectric Effect
Topic: photoelectric effect book example
Replies: 2
Views: 20

Re: photoelectric effect book example

It's a known value, likely to be provided on a test.
by chemboi
Mon Oct 28, 2019 12:28 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Electromagnetic Spectrum
Replies: 3
Views: 35

Re: Electromagnetic Spectrum

I think the spirit of this questions is enforcing the concept that the Balmer series is visible spectrum, and Lyman is UV.
by chemboi
Mon Oct 28, 2019 12:27 am
Forum: *Shrodinger Equation
Topic: wave function
Replies: 3
Views: 44

Re: wave function

I don't believe we are expected to know the equations that are the wave functions. Worth checking with your TA though.
by chemboi
Mon Oct 28, 2019 12:24 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: S and D Oribitals
Replies: 1
Views: 23

Re: S and D Oribitals

The half filling or ful filling (5 or 10 electrons) of 3d orbital is a lower energy state for the electrons to be in, with 4s having 1 electron, than 4s2 and 3d4 or 3d9. see here for explanation: https://chemistry.stackexchange.com/questions/53246/why-are-full-and-half-filled-orbitals-the-most-stabl...
by chemboi
Sat Oct 26, 2019 2:57 pm
Forum: Quantum Numbers and The H-Atom
Topic: Determining Element
Replies: 4
Views: 41

Re: Determining Element

I don't think its possible to pin down individual elements if you are only given n, l, m. Rather, these describe orbitals in elements of that n
by chemboi
Sun Oct 20, 2019 10:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ordering for different orbitals
Replies: 3
Views: 22

Re: Ordering for different orbitals

I think Dr. Lavelle said that it's arbitrary. Worth clarifying with him or your TA. Also, wouldn't that number of electrons correspond to oxygen?
by chemboi
Sun Oct 20, 2019 10:54 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Tungsten
Replies: 1
Views: 26

Re: Electron Configuration of Tungsten

It's a weird exception which intuition cannot help you out with very much as far as I know. Some rare earth metals are similarly bizarre. See this article for the in depth explanation: http://www.madsci.org/posts/archives/2000-02/951518136.Ch.r.html Points 3 and 4 explain tungsten: "As you go d...
by chemboi
Sun Oct 20, 2019 10:49 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions to the rules
Replies: 3
Views: 34

Re: Exceptions to the rules

In the cases of these atoms, a lower energy configuration is for each of the five 3d orbitals to be half-filled (Cr) or filled (Cu) and the 4s to have 1 electron rather than 2. I believe these energy level differences are quite small, so it is difficult to have an intuition for these exceptions beyo...
by chemboi
Sun Oct 20, 2019 10:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Hund's Rule
Replies: 5
Views: 48

Re: Hund's Rule

I believe that single electrons parallel spins occupying empty orbitals is a lower energy (more favorable) than pairing first. I'm not 100% sure why pairing-first filling is not favorable, but I think it has to do with the involved electron-electron repulsion in such a scenario.
by chemboi
Sun Oct 20, 2019 10:41 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Stern and Gerlach Experiment: Electron Spin
Replies: 3
Views: 19

Re: Stern and Gerlach Experiment: Electron Spin

I believe the setup for the experiment was using silver atoms, passed through a magnetic field. These neutral silver atoms have an unpaired electron, in the 5s state I believe. If there was no spin on the electrons to interact with the magnetic field, one would expect a majority of the silver atoms ...
by chemboi
Sat Oct 12, 2019 5:00 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H-Atom
Replies: 3
Views: 51

Re: H-Atom

To add on to the first response, the Bohr model works for atoms or ions with only one electron, so hydrogen or a rare C 5+ ion or He+ ion.
by chemboi
Sat Oct 12, 2019 4:54 pm
Forum: Photoelectric Effect
Topic: Question about the application of the effect
Replies: 2
Views: 49

Re: Question about the application of the effect

To add on to the previous response, as far as theoretical applications, the photoelectric experiment also indicated that the wave model of light alone could not explain all observed behaviors (such as the photoelectric effect).
by chemboi
Sat Oct 12, 2019 4:51 pm
Forum: Photoelectric Effect
Topic: work function clarification
Replies: 4
Views: 34

Re: work function clarification

Yes!
by chemboi
Sat Oct 12, 2019 4:48 pm
Forum: Properties of Light
Topic: Electromagnetic Radiation
Replies: 1
Views: 21

Re: Electromagnetic Radiation

Im not sure what the greatest observed wavelength is, but https://en.wikipedia.org/wiki/Extremely_low_frequency lists some EM waves as having wavelengths in the ballpark of 100,000 km!
by chemboi
Sat Oct 12, 2019 4:45 pm
Forum: Photoelectric Effect
Topic: Molecular Spectroscopy
Replies: 3
Views: 45

Re: Molecular Spectroscopy

To elaborate on the previous answer, the differential wavelength absorption of different elements leads to different atomic spectra (that rainbow spectrum looking rectangle with black lines) which is what molecular spectroscopy deals with
by chemboi
Thu Oct 03, 2019 8:56 pm
Forum: Significant Figures
Topic: clarificaition of sig figs
Replies: 3
Views: 33

Re: clarificaition of sig figs

From http://chemistry.bd.psu.edu/jircitano/sigfigs.html

"Non-zero digits are always significant.
Any zeros between two significant digits are significant.
A final zero or trailing zeros in the decimal portion ONLY are significant"
by chemboi
Thu Oct 03, 2019 8:55 pm
Forum: SI Units, Unit Conversions
Topic: unit conersations
Replies: 7
Views: 80

Re: unit conersations

Some calculations, such as those regarding wavelength, operate with units of meters, so watch out for those. In that case, if you are given some measure in centimeters, convert that value to meters to then use in your calculation.
by chemboi
Thu Oct 03, 2019 8:48 pm
Forum: Significant Figures
Topic: Sig figs in intermediate steps??
Replies: 5
Views: 34

Re: Sig figs in intermediate steps??

Rather than rounding in intermediate steps, preserve your decimal precision. Once you have your final answer, perhaps with many decimal places, express it according to sig fig restrictions present in the original problem.
by chemboi
Thu Oct 03, 2019 8:44 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percentage Composition Rounding
Replies: 3
Views: 34

Re: Mass Percentage Composition Rounding

In general, for intermediate calculation steps preserve a high degree of accuracy (don't chop decimals). If you were around 1% off of 100%, then excess rounding during calculations may be responsible.

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