Search found 96 matches

by Jialun Chen 4F
Fri Feb 28, 2020 10:29 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: electrolysis
Replies: 2
Views: 6

Re: electrolysis

Electrolysis or electrolytic cell has a negative Ecell potential overall, which makes it nonspontaneous. Examples would include the process of making gold and other metals, such as magnesium.
*According to my TA, the Galvanic cell (spontaneous) is what we should put more emphasis on.
by Jialun Chen 4F
Fri Feb 28, 2020 10:26 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Porous Disk and Salt Bridge
Replies: 10
Views: 274

Re: Porous Disk and Salt Bridge

I agree with the comments above. There's not a difference in efficiency between the two based on what I know of.
by Jialun Chen 4F
Fri Feb 28, 2020 10:23 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Calculating Standard Potentials
Replies: 4
Views: 31

Re: Calculating Standard Potentials

Use the equation ECathode - EAnode; in a Galvanic cell, the standard setup is having anode on the left (oxidation) and cathode on the right (reduction).
by Jialun Chen 4F
Fri Feb 28, 2020 10:21 pm
Forum: Balancing Redox Reactions
Topic: Test 2
Replies: 10
Views: 23

Re: Test 2

The second page of outline 4 (Thermodynamics) and all of the outline 5 (Electrochem).
by Jialun Chen 4F
Fri Feb 28, 2020 10:21 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneity
Replies: 10
Views: 15

Re: Spontaneity

In addition to the sign of Gibbs free energy, the sign of cell potential can also serve as an indicator: if Ecell is greater than zero, the reaction is spontaneous, vice versa.
by Jialun Chen 4F
Thu Feb 20, 2020 12:06 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Adding Inert Gas
Replies: 20
Views: 93

Re: Adding Inert Gas

Adding an inert gas (noble gases or gases that's not present in the reaction) increases the pressure of the system, but alters no concentration, thus having no effect on the overall reaction.
by Jialun Chen 4F
Thu Feb 20, 2020 12:04 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Midterm Q6B
Replies: 4
Views: 34

Re: Midterm Q6B

Since DeltaG=DeltaH-T*DeltaS, in order to have a nearly equivalent DeltaG and DeltaH means an insignificant DeltaS (disorder). Thus, A has 3 solids from reactant to 3 solids from the product, indicates DeltaS of the reaction is pretty much zero. Assuming constant temperature for the four reactions, ...
by Jialun Chen 4F
Wed Feb 19, 2020 11:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 23
Views: 96

Re: Spontaneous

DeltaG's sign determines spontaneity. If positive, not spontaneous; if negative, spontaneous; if =0, at equilibrium.
by Jialun Chen 4F
Wed Feb 19, 2020 11:58 pm
Forum: Administrative Questions and Class Announcements
Topic: Recommended Pathway for Chem Series
Replies: 12
Views: 91

Re: Recommended Pathway for Chem Series

It depends on your preference. Some choose to continue with 14C or taking 14C along with 14BL, but you can also choose to take the lab alone.
by Jialun Chen 4F
Wed Feb 19, 2020 11:56 pm
Forum: Balancing Redox Reactions
Topic: Test 2 [ENDORSED]
Replies: 12
Views: 89

Re: Test 2 [ENDORSED]

Test 2 is now week 9 during the discussion; it covers materials after midterm excluding kinetics.
by Jialun Chen 4F
Thu Feb 13, 2020 12:04 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 23
Views: 96

Re: Spontaneous

The sign of Gibb's free energy determines the spontaneity of a reaction.
by Jialun Chen 4F
Thu Feb 13, 2020 12:01 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy
Replies: 4
Views: 31

Re: Entropy

Since entropy is a measure of disorder, higher temperature means more disorder.
by Jialun Chen 4F
Wed Feb 12, 2020 11:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Irreversible Expansion
Replies: 7
Views: 50

Re: Irreversible Expansion

Irreversible expansion keeps the pressure constant. It is relatively faster than reversible expansion, yet less efficient because it does less work.
by Jialun Chen 4F
Wed Feb 12, 2020 11:35 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Significance of open, closed, isolated
Replies: 10
Views: 70

Re: Significance of open, closed, isolated

For a closed system, heat can be exchanged but volume remains constant. An open system has constant pressure yet a changing volume. An isolated system has no energy exchange whatsoever (eg. bomb calorimeter). So, in an isolated system, if it has no exchange of energy, can work be done? What would t...
by Jialun Chen 4F
Wed Feb 12, 2020 11:27 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Summary of Units
Replies: 3
Views: 36

Re: Summary of Units

LBacker_2E wrote:My TA said it is better to use kJ for ∆H, and J for the other values. Do you think this is really important, or is it just a preference?

To me, it seems to be a personal preference. Either would work.
by Jialun Chen 4F
Wed Feb 05, 2020 10:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp and Cv
Replies: 10
Views: 46

Re: Cp and Cv

There's no need to memorize the values. They'll be given if we even encounter related questions.
by Jialun Chen 4F
Wed Feb 05, 2020 10:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Significance of open, closed, isolated
Replies: 10
Views: 70

Re: Significance of open, closed, isolated

For a closed system, heat can be exchanged but volume remains constant. An open system has constant pressure yet a changing volume. An isolated system has no energy exchange whatsoever (eg. bomb calorimeter).
by Jialun Chen 4F
Wed Feb 05, 2020 10:29 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Topics on the Midterm
Replies: 22
Views: 101

Re: Topics on the Midterm

Everything for topics 1-4. I believe he said that he will begin and finish covering Gibbs free energy in the lecture this coming Wednesday and Friday. Does anyone know if we will be learning new things next week on Monday and Wednesday? I think Dr. Lavelle will go over past exam questions in class ...
by Jialun Chen 4F
Wed Feb 05, 2020 10:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 7
Views: 69

Re: Midterm

Andrew Liang 1I wrote:Are we expected to memorize any equations for the midterm or are they going to give all of them to us on the cover sheet?

I'm sure that all the formulas will be given on the cover sheet.
by Jialun Chen 4F
Wed Feb 05, 2020 10:26 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: Microstates
Replies: 7
Views: 41

Re: Microstates

My understanding is that the value is utilized to calculate entropy in the Boltzmann equation, which denotes as S=kblnW.
by Jialun Chen 4F
Tue Jan 28, 2020 1:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Thermochemistry Textbook HW
Replies: 4
Views: 33

Re: Thermochemistry Textbook HW

Personally I found 4D and 4E doable, but there might be more sections out there.
by Jialun Chen 4F
Tue Jan 28, 2020 1:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: qp vs qv
Replies: 6
Views: 28

Re: qp vs qv

I think what you stated is what constitutes the difference between those two q values.
by Jialun Chen 4F
Tue Jan 28, 2020 1:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 11
Views: 40

Re: Bond Enthalpies

I agree with McKenna. Due to the numbers given in the bond enthalpy chart being averages, this method is not as accurate relatively.
by Jialun Chen 4F
Tue Jan 28, 2020 1:09 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE BOX
Replies: 27
Views: 97

Re: ICE BOX

The cutoff is 10^-3. Yet in cases of weak acids and bases, one may want to check the % ionization to ensure the approximation is valid (i.e, the quadratic formula is still necessary if the final percentage is >5%).
by Jialun Chen 4F
Tue Jan 28, 2020 1:07 pm
Forum: Phase Changes & Related Calculations
Topic: Change in Temperature
Replies: 10
Views: 29

Re: Change in Temperature

Correct! Equilibrium constants change as the alteration of the temperature inside the system occurs.
by Jialun Chen 4F
Thu Jan 23, 2020 5:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Kw = (Ka)(Kb)
Replies: 4
Views: 24

Re: Kw = (Ka)(Kb)

Correct! 25 degree Celsius is the right temperature to assume.
by Jialun Chen 4F
Thu Jan 23, 2020 5:44 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: pKa/pKb and Ka/Kb
Replies: 5
Views: 25

Re: pKa/pKb and Ka/Kb

The relationship is analogous to that of pH/pOH and [H3O+]/[OH-].
Essentially,
10^-pKa=Ka (same applies for Kb)
pKa=-log(Ka) (same applies for Kb).
by Jialun Chen 4F
Thu Jan 23, 2020 5:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K value
Replies: 7
Views: 28

Re: K value

If K is less than 10^-3, you can drop the x in the denominator. I usually do a double-check afterwards by calculating the % ionization; if the % ionization is less than 5, you're good, otherwise, you would have to use the quadratic formula.
by Jialun Chen 4F
Thu Jan 23, 2020 5:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Delta H
Replies: 10
Views: 47

Re: Delta H

I agree with Caroline's answer. If positive Delta H, endothermic; if negative Delta H, exothermic.
by Jialun Chen 4F
Thu Jan 23, 2020 5:34 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: pKa/Pkb vs pH/pOH
Replies: 3
Views: 21

Re: pKa/Pkb vs pH/pOH

Though both pKa+pKb and pH+pOH equal to 14, Ka and Kb are constants indicating how well an acid or base dissociates, while [H+] and [OH-] represents the concentration of hydronium and hydroxide ions.
by Jialun Chen 4F
Thu Jan 16, 2020 10:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units in ICE Table
Replies: 8
Views: 40

Re: Units in ICE Table

I'm quite sure that all values inputted in ICE Table have to be converted into molarity (mol*L^-1).
by Jialun Chen 4F
Thu Jan 16, 2020 9:58 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier overview
Replies: 3
Views: 21

Re: Le Chatelier overview

All three aforementioned aspects. I recall that K remains unchanged when altering concentration and partial pressure, but when to increase or decrease the temperature, K changes.
by Jialun Chen 4F
Thu Jan 16, 2020 9:54 am
Forum: Ideal Gases
Topic: bars vs atm
Replies: 8
Views: 43

Re: bars vs atm

They are both units for measuring pressure. I think as long as your units in one question remain consistent, you're all set.
by Jialun Chen 4F
Thu Jan 16, 2020 9:53 am
Forum: Ideal Gases
Topic: Topics for Test 1
Replies: 17
Views: 110

Re: Topics for Test 1

The first two outlines should be the focus. Doing all/most of the homework problems, especially the focus questions, would definitely help a lot. Also, go back to read the textbook for any concepts that seem vague.
by Jialun Chen 4F
Thu Jan 16, 2020 9:50 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent Ionization
Replies: 11
Views: 69

Re: Percent Ionization

That is correct! And I believe that in homework problems the % ionization is under 5% excluding certain outliers.
by Jialun Chen 4F
Thu Jan 09, 2020 9:59 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Are Both L and Aq Excluded From Equilibrium Constant Expressions?
Replies: 4
Views: 34

Re: Are Both L and Aq Excluded From Equilibrium Constant Expressions?

Aqueous solutions should be included in the equilibrium expression. Only solid (s) and liquid (q) are excluded.
by Jialun Chen 4F
Thu Jan 09, 2020 9:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: units of K
Replies: 10
Views: 41

Re: units of K

Since it's a constant, not a variable, K does not have a unit. We can also think of this by perceiving the molarity units of products and reactant cancels.
by Jialun Chen 4F
Thu Jan 09, 2020 9:55 am
Forum: Ideal Gases
Topic: Understanding Q
Replies: 19
Views: 86

Re: Understanding Q

Correct. We perform the same calculation procedure when solving for Q and K.
by Jialun Chen 4F
Thu Jan 09, 2020 9:54 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changing Kc [ENDORSED]
Replies: 4
Views: 41

Re: Changing Kc [ENDORSED]

I think the equilibrium constant Kc does not change for the same reaction under the same temperature no matter what masses of reactants one uses.
by Jialun Chen 4F
Thu Jan 09, 2020 9:52 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solvents
Replies: 5
Views: 33

Re: Solvents

Since the change in concentration of the solvent is negligible, we don't include them in the equilibrium expression.
by Jialun Chen 4F
Tue Dec 03, 2019 12:06 am
Forum: General Science Questions
Topic: 50 post grade
Replies: 25
Views: 366

Re: 50 post grade

As long as you did 5 posts weekly and make sure changed our username to your legal name plus your discussion, I think you'll be fine.
by Jialun Chen 4F
Mon Dec 02, 2019 11:47 pm
Forum: Biological Examples
Topic: cisplatin
Replies: 5
Views: 93

Re: cisplatin

I agree with the answer above. It's also one of the biological examples Dr. Lavelle expects us to memorize.
by Jialun Chen 4F
Mon Dec 02, 2019 11:44 pm
Forum: Quantum Numbers and The H-Atom
Topic: Rydberg equation
Replies: 9
Views: 90

Re: Rydberg equation

You're allowed to use both, yet it depends on which one explains the concept better for you.
by Jialun Chen 4F
Mon Dec 02, 2019 11:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorization
Replies: 15
Views: 121

Re: Memorization

Yes, we do. I hypothesize the VSEPR questions on the final is going to resemble those from test 2.
by Jialun Chen 4F
Mon Dec 02, 2019 11:38 pm
Forum: Naming
Topic: Cyano vs. Cyanido
Replies: 2
Views: 26

Re: Cyano vs. Cyanido

There are two versions of naming, while the former is the older, the latter is the revised name.
by Jialun Chen 4F
Wed Nov 27, 2019 4:04 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: brackets
Replies: 13
Views: 72

Re: brackets

It means that everything inside the bracket is a part of the coordination compound.
by Jialun Chen 4F
Wed Nov 27, 2019 4:02 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Test #2 handback
Replies: 11
Views: 85

Re: Test #2 handback

It will be handed back during your discussion session. If your discussion is on Wed, Thurs, of Fri, you will probably get the physical copy back in your discussion session next week.
by Jialun Chen 4F
Wed Nov 27, 2019 4:00 am
Forum: Lewis Acids & Bases
Topic: Identifying Acids and Bases
Replies: 8
Views: 41

Re: Identifying Acids and Bases

I agree with Mashkinadze's answer. I personally just memorize the specific strong acids/bases.
by Jialun Chen 4F
Wed Nov 27, 2019 3:29 am
Forum: Hybridization
Topic: sigma or pi?
Replies: 20
Views: 115

Re: sigma or pi?

Just memorize:
single bond: one sigma bond
double bond: one sigma bond, one pi bond
triple bond: one sigma bond, 2 pi bonds
by Jialun Chen 4F
Wed Nov 27, 2019 3:27 am
Forum: Hybridization
Topic: Hybridization of PF5
Replies: 4
Views: 37

Re: Hybridization of PF5

Since F has 3 lone pairs and one bonded pairs, the electron density is thus tetrahedral, leads to hybridization of sp3.
by Jialun Chen 4F
Thu Nov 21, 2019 3:02 am
Forum: Hybridization
Topic: for test 2
Replies: 7
Views: 59

Re: for test 2

Hybridization is not gonna be on Test 2.
by Jialun Chen 4F
Thu Nov 21, 2019 3:01 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: cisplatin
Replies: 4
Views: 43

Re: cisplatin

The positions of the cl- ions are different between cisplatin and transplatin. For cis, the two cl- are on the same side, thus dipole moments doesn't cancel. The two Cl- thus bond with the N of the guanine base pair (forming two bonds).
by Jialun Chen 4F
Thu Nov 21, 2019 12:27 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 6
Views: 45

Re: Bond Angles

That is correct. For instance, compounds with AX4 (tetrahedral) formula would have bond angles of 120 degrees, while AX3E (trigonal pyramidal) would have bond angles of slightly less than 120 degrees due to the lone pair.
by Jialun Chen 4F
Thu Nov 21, 2019 12:22 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle of bent
Replies: 17
Views: 97

Re: Bond Angle of bent

Sorry, I should've clarified: for AX2E2, the bond angle is going to be slightly less than 109.5 degrees, while AX2E is less than 120 degrees. Both VSEPR formula represents bent/angular shape.
by Jialun Chen 4F
Thu Nov 21, 2019 12:18 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle of bent
Replies: 17
Views: 97

Re: Bond Angle of bent

It's gonna be less than 109.5 degrees because of the lone pair.
by Jialun Chen 4F
Thu Nov 21, 2019 12:15 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Melting Point
Replies: 3
Views: 42

Re: Melting Point

I think melting points share the same trend as boiling points. As atom size gets larger, more polarizable, thus stronger London forces leads to higher melting point.
by Jialun Chen 4F
Thu Nov 14, 2019 1:43 am
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 vs. Ion-Dipole
Replies: 2
Views: 38

Re: Dipole-Dipole vs. Ion-Dipole

For ion-dipole, you have an ion which carries a charge, thus it has to be considered when evaluating IMF, while dipole-dipole solely depends on dipole moment and size of the molecule.
by Jialun Chen 4F
Thu Nov 14, 2019 1:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorization
Replies: 15
Views: 121

Re: Memorization

Yup, I'm quite sure that's the majority content on Test 2.
by Jialun Chen 4F
Thu Nov 14, 2019 1:36 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Problem 3F.5
Replies: 3
Views: 50

Re: Problem 3F.5

The dominant force to be considered in 3F 5(c) is the dipole-dipole force, which depends on the size of the molecule; since Iodine is larger than Fluorine, Iodine experience higher diploe moment, which results in a stronger dipole-dipole force.
by Jialun Chen 4F
Wed Nov 13, 2019 9:37 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 22
Views: 275

Re: Test #2

CandiceNourian1J wrote:Do you think it will also have some information from the midterm as well? Or only new untested topics?

I don't think so, but we should know the basics from the past materials, such as drawing lewis structures.
by Jialun Chen 4F
Wed Nov 13, 2019 9:35 pm
Forum: Student Social/Study Group
Topic: Test 2
Replies: 7
Views: 77

Re: Test 2

The test will be in your discussion section next week. The topic covered is everything after the midterm, which includes IMFs and VSPER models/shapes.
by Jialun Chen 4F
Wed Nov 06, 2019 11:58 pm
Forum: Resonance Structures
Topic: resonance hybrid
Replies: 6
Views: 43

Re: resonance hybrid

I don't think it's necessary to know to draw a hybrid, but we are expected know the concept.
by Jialun Chen 4F
Wed Nov 06, 2019 11:54 pm
Forum: Bond Lengths & Energies
Topic: Bond lengths
Replies: 4
Views: 35

Re: Bond lengths

Bond strength increases from single bonds to triple bonds, and bond length is the opposite, which decreases from single bonds to triples bonds.
by Jialun Chen 4F
Wed Nov 06, 2019 11:49 pm
Forum: Quantum Numbers and The H-Atom
Topic: Rydberg equation
Replies: 9
Views: 90

Re: Rydberg equation

You can use that equation, but the energy version that's given by Dr. Lavelle explains the concept better for me.
by Jialun Chen 4F
Tue Nov 05, 2019 2:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Midterm review
Replies: 5
Views: 67

Re: Midterm review

You're very welcome, I am glad that helped. Good luck studying!
by Jialun Chen 4F
Tue Nov 05, 2019 2:20 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Midterm review
Replies: 5
Views: 67

Re: Midterm review

Personally, I write down the equations and concepts a notecard and I go back to them as I finish reviewing each section.
by Jialun Chen 4F
Thu Oct 31, 2019 1:43 am
Forum: Electronegativity
Topic: Electronegativity trends
Replies: 5
Views: 33

Re: Electronegativity trends

It's definitely a trend you need to remember along with the atomic radius, I.E., and electron affinity. Yet it's unnecessary to memorize all the values.
by Jialun Chen 4F
Thu Oct 31, 2019 1:41 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: What are the octet exceptions?
Replies: 11
Views: 76

Re: What are the octet exceptions?

The first four elements, which are H, He, Li, and Be, are the exceptions to the octet rule.
by Jialun Chen 4F
Thu Oct 31, 2019 1:37 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: D orbital
Replies: 5
Views: 40

Re: D orbital

That's correct. The d-orbital can hold 5 pairs of or 10 electrons.
by Jialun Chen 4F
Thu Oct 31, 2019 1:36 am
Forum: Ionic & Covalent Bonds
Topic: Midterm
Replies: 10
Views: 102

Re: Midterm

All you need to bring is a pen, a scientific calculator, and your ID. Depending on your last name, the location is gonna be different, check out Dr. Lavelle's website for details.
by Jialun Chen 4F
Thu Oct 31, 2019 1:32 am
Forum: Resonance Structures
Topic: Why do all of the bonds have the same length regardless of double/single bonds in a resonance structure?
Replies: 4
Views: 40

Re: Why do all of the bonds have the same length regardless of double/single bonds in a resonance structure?

It's because the resonance hybrid is the actual representation of the structure, which has the same length. While the "alternatives" have different length in double/single bonds, but those are not actual structures.
by Jialun Chen 4F
Thu Oct 24, 2019 12:02 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: ground state
Replies: 6
Views: 62

Re: ground state

There's one difference I noted when Dr. Lavelle talked about the periodic trends. He lectured about electron affinity but didn't mention electronegativity; I searched them up and found out they're different concepts: electron affinity is the energy released when electrons are added to gas-phase atom...
by Jialun Chen 4F
Wed Oct 23, 2019 10:55 pm
Forum: Ionic & Covalent Bonds
Topic: Octet Rule
Replies: 6
Views: 57

Re: Octet Rule

They don't have enough electrons to complete an octet if I recalled correctly.
by Jialun Chen 4F
Wed Oct 23, 2019 10:42 pm
Forum: Resonance Structures
Topic: defintion
Replies: 7
Views: 75

Re: defintion

That's correct. Resonance refers to lewis structure have multiple bonds in different equivalent locations.
by Jialun Chen 4F
Wed Oct 23, 2019 10:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: ground state
Replies: 6
Views: 62

Re: ground state

The ground state is the stabilized state, the opposite of excited state. I always use the noble/inert gas to represent the inner electrons and write out the valence electrons. For example, the electron configuration for Chlorine is [Ne]3s2 3p6.
by Jialun Chen 4F
Wed Oct 23, 2019 10:34 pm
Forum: Ionic & Covalent Bonds
Topic: What topic are we on?
Replies: 11
Views: 116

Re: What topic are we on?

I'm pretty sure that you will be fine to submit problems from either quantum or chemical bonding section, or both.
by Jialun Chen 4F
Tue Oct 15, 2019 10:11 pm
Forum: Einstein Equation
Topic: E=hv
Replies: 43
Views: 2323

Re: E=hv

E=hv is the incoming energy of electromagnetic radiation (photon). The energy needed to remove electron is the work function (represented by a greek alphabet).
by Jialun Chen 4F
Tue Oct 15, 2019 10:08 pm
Forum: DeBroglie Equation
Topic: Calculating Wavelength
Replies: 5
Views: 65

Re: Calculating Wavelength

I got the same conclusion/answer as AArmellini did. There is no difference when I used 3 sig.figs in that problem.
by Jialun Chen 4F
Tue Oct 15, 2019 10:04 pm
Forum: Properties of Light
Topic: Variables and what they mean
Replies: 9
Views: 76

Re: Variables and what they mean

Lambda represents wavelength and v (squiggly) stands for frequency. It's kind easy to mix up frequency and velocity (velocity's variable is lower-case v).
by Jialun Chen 4F
Tue Oct 15, 2019 10:01 pm
Forum: Einstein Equation
Topic: Einstein Equation
Replies: 3
Views: 22

Re: Einstein Equation

I agree with the answer above that E=hv is the equation used to calculate energy per photon. h is Planck's constant and v is frequency.
by Jialun Chen 4F
Tue Oct 15, 2019 9:58 pm
Forum: Photoelectric Effect
Topic: Speed of Light
Replies: 29
Views: 210

Re: Speed of Light

The speed of light is in fact a constant. I used to use 2.9979*10^8 more often but figured 2.998*10^8 is more commonly applied in this class.
by Jialun Chen 4F
Thu Oct 10, 2019 2:23 am
Forum: Limiting Reactant Calculations
Topic: Net Ionic Equation
Replies: 6
Views: 93

Re: Net Ionic Equation

For that' you might want to review the solubility of substances and review the definition of a spectator ion.
by Jialun Chen 4F
Thu Oct 10, 2019 2:20 am
Forum: SI Units, Unit Conversions
Topic: Angstrom
Replies: 16
Views: 214

Re: Angstrom

I would recommend familiarizing yourself with all the units to play it safe. An Angstrom is simply a measurement that is equivalent to 10^-10m (or 0.1 nm if you prefer).
by Jialun Chen 4F
Wed Oct 09, 2019 9:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals G
Replies: 4
Views: 52

Re: Fundamentals G

I personally use the mole to mole conversion: 1 mole of CuSO4.5H2O contains 5 moles of H2O.
by Jialun Chen 4F
Wed Oct 09, 2019 9:38 pm
Forum: Empirical & Molecular Formulas
Topic: How to format formulas
Replies: 4
Views: 86

Re: How to format formulas

There's actually something called the hill system that states C atoms and H atoms should be placed first, and others follow in alphabetical order.
by Jialun Chen 4F
Wed Oct 09, 2019 9:31 pm
Forum: SI Units, Unit Conversions
Topic: Test 1
Replies: 9
Views: 148

Re: Test 1

The test covers materials from the Review of Chemical & Physical Principles, which are some of the fundamental sections, so I believe the dilution equation is a subject that's likely to be tested.
by Jialun Chen 4F
Sun Oct 06, 2019 8:27 pm
Forum: SI Units, Unit Conversions
Topic: 50 Min test
Replies: 4
Views: 50

Re: 50 Min test

It's during your discussion. So if you have discussion on Tuesday, the test is gonna be on the same day. I recommend doing problems from the assigned homework list to prepare.
by Jialun Chen 4F
Thu Oct 03, 2019 11:55 pm
Forum: General Science Questions
Topic: Chem 17 vs. Chem 14A
Replies: 1
Views: 19

Re: Chem 17 vs. Chem 14A

It depends on the content your high school teacher covered in honors chem because unlike AP chem, honors chem can be very distinct from school to school. If you are familiar with most of the content in the fundamental section, you are probably in good shape; if not, you might want to spend a decent ...
by Jialun Chen 4F
Tue Oct 01, 2019 12:19 am
Forum: Significant Figures
Topic: Significant Figures usage confusion
Replies: 6
Views: 70

Re: Significant Figures usage confusion

You are very welcome! I am glad that helped.
by Jialun Chen 4F
Tue Oct 01, 2019 12:07 am
Forum: Significant Figures
Topic: Significant Figures usage confusion
Replies: 6
Views: 70

Re: Significant Figures usage confusion

Addition and subtraction have a slightly different rule: you utilize the smallest decimal places instead of the smallest sig figs.
by Jialun Chen 4F
Tue Oct 01, 2019 12:00 am
Forum: Significant Figures
Topic: Significant Figures usage confusion
Replies: 6
Views: 70

Re: Significant Figures usage confusion

For multiplication and division, the answer should have the same significant figure as the smaller number. For e.g., 2.0 mol/2.00L= 1.0M.
by Jialun Chen 4F
Sun Sep 29, 2019 11:57 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Accuracy vs Precision
Replies: 10
Views: 134

Re: Accuracy vs Precision

Precision is how close to each other the measurements are. You can have high precision but still got a bad lab trial because of both data are flawed. Accuracy is how close measurements are to the correct value.
by Jialun Chen 4F
Sun Sep 29, 2019 8:30 pm
Forum: Significant Figures
Topic: Question About Significant Figures and Rounding
Replies: 22
Views: 336

Question About Significant Figures and Rounding

I remain a little ambiguous when it comes to applying sig figs. Can someone clarify when is it appropriate to round, when do we keep the entire digit, and when are we supposed to use sig figs?
by Jialun Chen 4F
Sun Sep 29, 2019 3:59 pm
Forum: Administrative Questions and Class Announcements
Topic: Formatting homework
Replies: 12
Views: 161

Re: Formatting homework

I am doing mine on binder papers. And after I finished all my works, I plan to choose five problems and rewrite them on a separate sheet to turn in for credit. I also have a tiny folder for this class specifically to keep all my papers.
by Jialun Chen 4F
Sat Sep 28, 2019 5:28 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Avogradro's Number [ENDORSED]
Replies: 5
Views: 181

Re: Avogradro's Number [ENDORSED]

Try to think 1 mole as 1 dozen. Just as one dozen refers to 12 of some object, 1 mole refers to 6.022*10^23 of something. Avogadro's number is simply 6.022*10^23. Hope this can help.
by Jialun Chen 4F
Fri Sep 27, 2019 7:05 pm
Forum: Empirical & Molecular Formulas
Topic: Formulas
Replies: 10
Views: 893

Re: Formulas

To find the molecular formula, you have to find the molar mass empirical formula first. Then, use the molar mass of the molecular formula to divide the molar mass of the empirical formula, that would give you a whole number (or nearly). Finally, use the whole number to multiply the # of atoms in emp...

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