Search found 112 matches

by chrisleung-2J
Fri Mar 13, 2020 8:10 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Endgame 12
Replies: 1
Views: 30

Re: Endgame 12

You can determine if a molecule is a catalyst by looking at how it appears throughout the steps of a reaction. If the species appears first as a reactant which is consumed and then in a later step reappears as a product, it would be considered a catalyst.
by chrisleung-2J
Fri Mar 13, 2020 8:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Final
Replies: 11
Views: 143

Re: Final

I believe that Professor Lavelle is still determining the exact amount of time to be alotted for us to complete the final, but from what I recall it is supposed to begin at the same time as the in-person exam would have (11:30 AM this Sunday) and last for 3-4 hours.
by chrisleung-2J
Fri Mar 13, 2020 8:08 pm
Forum: Student Social/Study Group
Topic: thoughtful poetry time + lavelle appreciation
Replies: 6
Views: 165

Re: thoughtful poetry time + lavelle appreciation

Thank you for all that you do, Professor Lavelle. We all greatly appreciate how communicative you have been with us throughout this difficult time and your willingness to make changes in order to accommodate this complex situation!
by chrisleung-2J
Fri Mar 13, 2020 8:07 pm
Forum: Administrative Questions and Class Announcements
Topic: take home FINAL DEADLINE
Replies: 15
Views: 305

Re: take home FINAL DEADLINE

I believe that the take-home final is supposed to be taken during the same time as the in-class one, which is this Sunday from 11:30AM - 2:30PM.
by chrisleung-2J
Fri Mar 13, 2020 8:05 pm
Forum: Environment, Ozone, CFCs
Topic: NO3
Replies: 4
Views: 55

Re: NO3

Yes, it is correct that because NO3 is a catalyst it would not be included in the overall rxn equation.
by chrisleung-2J
Tue Mar 10, 2020 9:45 am
Forum: Biological Examples
Topic: adsorbtion
Replies: 4
Views: 59

Re: adsorbtion

I believe so, as adsorption refers to the physical contact of reactants with the surface of a catalyst in a different state. If the catalyst were homogeneous I believe that we wouldn't consider the contact to be adsorption since there is no such contact between substances of different physical states.
by chrisleung-2J
Sun Mar 08, 2020 4:40 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate Laws
Replies: 3
Views: 32

Re: Rate Laws

I believe we would exclude H2O since it has a uniform concentration
by chrisleung-2J
Fri Mar 06, 2020 5:50 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert electrode
Replies: 9
Views: 79

Re: Inert electrode

Inert electrodes are necessary if either of the redox equations doesn't involve a conducting solid.
by chrisleung-2J
Fri Mar 06, 2020 5:45 pm
Forum: Balancing Redox Reactions
Topic: spontaneous redox reactions
Replies: 4
Views: 60

Re: spontaneous redox reactions

This is because if the reaction is nonspontaneous than work energy must be expended in order to drive the reaction, so the work released by the reaction is essentially negative.
by chrisleung-2J
Wed Mar 04, 2020 6:21 pm
Forum: Balancing Redox Reactions
Topic: Simplifying
Replies: 7
Views: 106

Re: Simplifying

I think that after adding the half-rxn equations to get the overall redox equation we should technically simplify it if possible. However, in most cases I don't think we need to do further simplification since both charge and the number of atoms of each element should already be balanced.
by chrisleung-2J
Wed Mar 04, 2020 12:53 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: adding Pt
Replies: 1
Views: 30

Re: adding Pt

I believe that we could not have a solid I2 electrode due to the fact that I2 is a nonmetal and is not a good conductor of electricity. As such, we would need another inert electrode to function as the conducting solid for this scenario
by chrisleung-2J
Tue Mar 03, 2020 2:50 pm
Forum: First Order Reactions
Topic: 1st, 2nd, and 0 Order Reactions
Replies: 2
Views: 58

Re: 1st, 2nd, and 0 Order Reactions

We did an example in class a few days ago showing how we can determine the order of individual reactants using a table of concentrations of each reactant and the resulting rate of reaction. The sum of the order of each individual reactant equals the overall order of the reaction.
by chrisleung-2J
Sun Mar 01, 2020 5:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs Electrolytic Cell
Replies: 1
Views: 31

Re: Galvanic vs Electrolytic Cell

I think we just need to memorize that a Galvanic cell has a negative anode and a positive cathode, while the charges are flipped for an electrolytic cell.
by chrisleung-2J
Sun Mar 01, 2020 5:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrochemical Series
Replies: 3
Views: 38

Re: Electrochemical Series

I believe that this refers to the list of reduction reactions and their potentials that we are provided. By "understanding them" I believe it just means knowing how to read them and use them.
by chrisleung-2J
Sun Mar 01, 2020 5:39 pm
Forum: Balancing Redox Reactions
Topic: Anode and Cathode
Replies: 8
Views: 65

Re: Anode and Cathode

The reduction reaction always occurs at the cathode, and the oxidation reaction is the anode.
by chrisleung-2J
Sun Mar 01, 2020 5:07 pm
Forum: Balancing Redox Reactions
Topic: reversible reactions
Replies: 2
Views: 37

Re: reversible reactions

I believe you'd use the oxidation and reduction equations that yield the highest overall positive Eº value
by chrisleung-2J
Sun Mar 01, 2020 1:04 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Flipping the sign
Replies: 10
Views: 82

Re: Flipping the sign

Yes, if you are given the reduction equation and reduction potential, you would flip the equation and the sign of Eº for the oxidation equation and oxidation potential.
by chrisleung-2J
Tue Feb 25, 2020 1:11 am
Forum: Balancing Redox Reactions
Topic: adding e-
Replies: 7
Views: 73

Re: adding e-

Once you determine the side electrons must go on for one of the half rxns, you can know to place the electrons on the opposite side of the other half rxn equation since the electrons must cancel as the equations are added.
by chrisleung-2J
Tue Feb 25, 2020 1:08 am
Forum: Administrative Questions and Class Announcements
Topic: midterm solutions
Replies: 4
Views: 91

Re: midterm solutions

If you have questions about MC portions of the midterm I'm sure you could get help with them on this platform as well!
by chrisleung-2J
Tue Feb 25, 2020 1:06 am
Forum: Balancing Redox Reactions
Topic: Reactions with compounds
Replies: 1
Views: 31

Re: Reactions with compounds

I believe all the still normal balancing rules still apply. A common one I've seen before is the reduction of Cr2O72- -> Cr+3
by chrisleung-2J
Tue Feb 25, 2020 1:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic/voltaic cell
Replies: 6
Views: 59

Re: Galvanic/voltaic cell

A galvanic cell has electron flow spontaneously, while an electrolytic cell requires an input of energy for the redox reaction to occur
by chrisleung-2J
Tue Feb 25, 2020 1:03 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 6
Views: 81

Re: Salt Bridge

I'm not sure what a biological example of a salt bridge would be, as the salt bridge usually just contains a salt with one positive and one negative ion
by chrisleung-2J
Thu Feb 13, 2020 4:49 pm
Forum: Phase Changes & Related Calculations
Topic: change in entropy
Replies: 7
Views: 204

Re: change in entropy

If delta S is less than zero, this means that the system is becoming more ordered through the process, thereby decreasing entropy.
by chrisleung-2J
Thu Feb 13, 2020 4:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm Curve
Replies: 45
Views: 504

Re: Midterm Curve

Yes, I don't believe individual exam scores are curved, but rather that the final grade boundaries are determined based on the overall performance of the class after the final.
by chrisleung-2J
Tue Feb 11, 2020 2:25 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Units for Heat Capacity & Specific Heat Capacity
Replies: 2
Views: 87

Units for Heat Capacity & Specific Heat Capacity

Is there a standard form of the units for calculations where we find a value for either of these? For example, could we leave the answer in kJ/°C or J/K for heat capacity, or would we always need to have it in the form J/°C?
by chrisleung-2J
Tue Feb 11, 2020 12:10 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Modeling Isobaric and Isochoric Systems
Replies: 1
Views: 34

Modeling Isobaric and Isochoric Systems

How would we model an isobaric system? I understand that an isobaric system has constant pressure, but how would the volume be changing if the pressure is constant? In the case of a cylinder with the piston, does the constant pressure refer to the pressure exerted by the piston and would we be seein...
by chrisleung-2J
Sun Feb 09, 2020 8:29 pm
Forum: Ideal Gases
Topic: reversing reactions
Replies: 14
Views: 177

Re: reversing reactions

When a reaction is reversed, K -> 1/K
by chrisleung-2J
Sun Feb 09, 2020 8:08 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: Degeneracy
Replies: 5
Views: 57

Re: Degeneracy

I believe that this equation, as well as the one used to calculate degeneracy when given # of molecules and # of microstates, would be the main ways in which we might be expected to apply this concept.
by chrisleung-2J
Sat Feb 08, 2020 2:16 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Molar Entropy
Replies: 3
Views: 38

Re: Molar Entropy

I believe the degeneracy takes precedence over the molecular weight
by chrisleung-2J
Sat Feb 08, 2020 2:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeters
Replies: 17
Views: 365

Re: Calorimeters

A bomb calorimeter only maintains constant volume, causing no work to result from pressure or volume changes and thereby resulting in all measured heat directly correlating with the change in internal energy.
by chrisleung-2J
Sat Feb 08, 2020 2:07 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous rxns
Replies: 3
Views: 38

Re: Spontaneous rxns

I'm not sure if this is true for all cases, as I thought of the example of a solute dissolving in water which could be a spontaneous process with minimal to no measurable change in volume
by chrisleung-2J
Sat Feb 08, 2020 2:06 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy of ice and liquid water
Replies: 3
Views: 36

Re: Gibbs free energy of ice and liquid water

I believe that this is able to occur since Gibbs Free Energy is measured at constant temperature and pressure, and in this case I believe the constant temp would be 0º C causing the rate of ice melting to equal the rate of water freezing, causing no net change in entropy or enthalpy at equilibrium
by chrisleung-2J
Sun Feb 02, 2020 11:02 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous vs. Energetically Favorable
Replies: 3
Views: 24

Re: Spontaneous vs. Energetically Favorable

Energetically favorable reactions tend to be spontaneous, as having a negative delta H value and a positive delta S value results in a negative delta G value
by chrisleung-2J
Sun Feb 02, 2020 10:58 pm
Forum: Calculating Work of Expansion
Topic: Calculus in Chemistry
Replies: 1
Views: 22

Re: Calculus in Chemistry

I don't think we really need to apply deep concepts from calculus in this class. The only thing that has come up thus far is a definite integral, but I believe that was more for illustration purposes and not very necessary for application.
by chrisleung-2J
Sun Feb 02, 2020 10:55 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated system
Replies: 10
Views: 152

Re: Isolated system

I believe that realistically a hydroflask would be considered a closed system, but in question 4A.1 it was established that a "very-high-quality thermos bottle" is an isolated system
by chrisleung-2J
Sun Feb 02, 2020 10:53 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4A.1
Replies: 2
Views: 35

Re: 4A.1

Coolant in a refrigerator coil is a closed system but not isolated since it likely allows for some leakage of heat with the surroundings. Likewise, a plant can be considered an open system because it allows for the exchange of gases and heat with the surroundings.
by chrisleung-2J
Sun Feb 02, 2020 10:50 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous
Replies: 4
Views: 58

Re: Spontaneous

Reactions are favorable when they increase entropy and decrease enthalpy for the system, and favorable reactions tend to be spontaneous
by chrisleung-2J
Sun Feb 02, 2020 10:49 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4A.11
Replies: 1
Views: 30

Re: 4A.11

For this problem, we are calculating the heat capacity of the calorimeter, which essentially incorporating both the specific heat of the solution in it and the specific heat of the calorimeter itself. As such, we essentially solve for mc in q=mc(delta)T, and the units are J/g
by chrisleung-2J
Sat Jan 25, 2020 8:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: equilibrium
Replies: 3
Views: 39

Re: equilibrium

I believe that any reversible chemical reaction can theoretically establish equilibrium.
by chrisleung-2J
Sat Jan 25, 2020 8:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculation methods
Replies: 6
Views: 49

Re: Calculation methods

I believe that Method 3 and Method 4 above are essentially the same, and that Dr. Lavelle was using the example of ethanol formation to illustrate the formula stated as "Method 4"
by chrisleung-2J
Sat Jan 25, 2020 8:06 pm
Forum: Phase Changes & Related Calculations
Topic: Celsius and Kelvin
Replies: 11
Views: 86

Re: Celsius and Kelvin

Most formulas in chemistry employ temperature measured in Kelvin, which can be found using the formula K = C + 273
by chrisleung-2J
Sat Jan 25, 2020 8:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka of strong acid
Replies: 3
Views: 42

Re: Ka of strong acid

Strong acids have Ka values which are many times larger than 1. For comparing two acids, the one with the higher Ka value is the one which is more dissociated and is therefore relatively stronger.
by chrisleung-2J
Sat Jan 25, 2020 7:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy Method
Replies: 5
Views: 43

Re: Bond Enthalpy Method

This is because all bond enthalpies except those of diatomic molecules are averages from multiple molecule structures containing the bond, and thus may not be perfectly accurate reflections of the bond energy for a specific molecule which may have other species altering the bond in question.
by chrisleung-2J
Thu Jan 16, 2020 6:25 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: change in temp
Replies: 4
Views: 40

Re: change in temp

We can treat the heat term when written in the equation in a very similar manner as a standard product or reactant. If the reaction is endothermic, the heat term would be written on the reactants side of the forward reaction, and increasing the temperature has a similar effect as increasing the conc...
by chrisleung-2J
Thu Jan 16, 2020 5:05 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Product Yield
Replies: 6
Views: 57

Re: Product Yield

If it is an equilibrium system, removing some of the gas or aqueous product that has formed can cause the system to shift right and produce additional product.
by chrisleung-2J
Thu Jan 16, 2020 5:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endo/Exothermic Reactions
Replies: 6
Views: 73

Re: Endo/Exothermic Reactions

I believe that the heat change of a reaction is case-specific, but I believe that decomposition reactions such as this tend to be endothermic since energy is required to break bonds.
by chrisleung-2J
Thu Jan 16, 2020 5:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acids and Bases
Replies: 2
Views: 27

Re: Acids and Bases

pH is a measurement of the concentration of H+ ions. As [H+] increases, pH decreases, and vice versa.
by chrisleung-2J
Thu Jan 16, 2020 5:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert gas
Replies: 4
Views: 27

Re: Inert gas

An inert gas is any gas that doesn't react despite being present in the system. Noble gases are almost always inert.
by chrisleung-2J
Mon Jan 13, 2020 4:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Exam Conflict
Replies: 1
Views: 40

Midterm Exam Conflict

Is it possible for us to arrange to take the Midterm exam at a different date & time than the scheduled one if we have a conflict?
by chrisleung-2J
Sun Jan 12, 2020 5:53 pm
Forum: General Science Questions
Topic: Test 1 [ENDORSED]
Replies: 13
Views: 180

Re: Test 1 [ENDORSED]

I don't think it will be during Week 2, as Professor Lavelle hasn't mentioned it in lecture yet.
by chrisleung-2J
Sun Jan 12, 2020 5:50 pm
Forum: Ideal Gases
Topic: Review Ideal Gas
Replies: 1
Views: 27

Re: Review Ideal Gas

That may be a good idea, as I believe we cover kinetics sometime this quarter
by chrisleung-2J
Sun Jan 12, 2020 5:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 21
Views: 206

Re: Units for K

Neither K nor Q have units
by chrisleung-2J
Sun Jan 12, 2020 5:49 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K
Replies: 6
Views: 76

Re: Q and K

K is the equilibirum constant, calculated using the formula [Products]/[Reactants] when the concentrations of both are at equilibrium. Q is calculated using the same formula, but the concentrations of both the products and reactants do not necessarily need to be at equilibirum. We use Q and K to det...
by chrisleung-2J
Sun Jan 12, 2020 5:45 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Chatelier's Principle
Replies: 7
Views: 62

Re: Chatelier's Principle

Le Chatelier's Principle refers to the concept that equilibrium systems shift in order to partially counteract disturbances to the existing state of equilibrium.
by chrisleung-2J
Sun Dec 08, 2019 12:31 am
Forum: Hybridization
Topic: Lone Pair Hybridization
Replies: 3
Views: 141

Re: Lone Pair Hybridization

you only write out the coefficient (the 2 in 2sp3) when involved in a bond where the quantum number involved in the bond is needed. lone pairs don't need the coefficient because they aren't involved in a bond where the quantum number needs to be specified. How would we know when the quantum number ...
by chrisleung-2J
Sun Dec 08, 2019 12:31 am
Forum: Hybridization
Topic: Lone Pair Hybridization
Replies: 3
Views: 141

Re: Lone Pair Hybridization

you only write out the coefficient (the 2 in 2sp3) when involved in a bond where the quantum number involved in the bond is needed. lone pairs don't need the coefficient because they aren't involved in a bond where the quantum number needs to be specified. How would we know when the quantum number ...
by chrisleung-2J
Sun Dec 08, 2019 12:02 am
Forum: Naming
Topic: naming
Replies: 2
Views: 55

Re: naming

The -ate suffix is added to the name for the transition metal when naming anionic ligands
by chrisleung-2J
Sun Dec 08, 2019 12:00 am
Forum: Hybridization
Topic: Lone Pair Hybridization
Replies: 3
Views: 141

Lone Pair Hybridization

When writing the hybridization for a lone pair, do we include a number for the energy level of the lone pair? For example, would we write the hybridization for a theoretical lone pair on an oxygen atom double-bonded to a carbon atom as Osp² or O2sp²?
by chrisleung-2J
Sat Dec 07, 2019 8:26 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: chelating ligands [ENDORSED]
Replies: 21
Views: 6227

Re: chelating ligands [ENDORSED]

Would it be correct, then, to say that “Ligand C is capable of chelating due to its atoms with lone pairs having an Ortho arrangement”?
by chrisleung-2J
Fri Dec 06, 2019 9:38 pm
Forum: Naming
Topic: How to find out the oxidation number?
Replies: 3
Views: 65

Re: How to find out the oxidation number?

Oxidation numbers can usually be determined by considering the oxidation number of known atoms to find those that are unknown. For example, O typically has an oxidation number of -2 and H typically has an oxidation number of +1, so in HNO3, which is neutral overall, we can use algebra to determine t...
by chrisleung-2J
Fri Dec 06, 2019 9:35 pm
Forum: Lewis Acids & Bases
Topic: 6.13
Replies: 1
Views: 36

Re: 6.13

Boron normally forms 3 bonds when it makes compounds. However, Lewis Acid-Base reacitons are the specific time when Boron is able to react and achieve a full octet by accepting two electrons from another atom or compound.
by chrisleung-2J
Fri Dec 06, 2019 9:34 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH in increasing temp
Replies: 2
Views: 45

Re: pH in increasing temp

I don't think this is really necessary to know for this course. However, I believe the answer is dependent on how the ionization of H2O is impacted by the changes in temp.
by chrisleung-2J
Fri Dec 06, 2019 9:33 pm
Forum: Lewis Acids & Bases
Topic: In a neutralization reaction, are there still lewis acids/bases?
Replies: 2
Views: 49

Re: In a neutralization reaction, are there still lewis acids/bases?

I think most Lewis Acid-Lewis Base rxns we have considered don't necessarily produce H2O since they involve the transfer of electrons to produce a final product.
by chrisleung-2J
Tue Dec 03, 2019 10:53 pm
Forum: Ionic & Covalent Bonds
Topic: polarity of shapes
Replies: 4
Views: 159

Re: polarity of shapes

I believe it would have the bond angles very similar or identical to an octahedron because the lone pairs are located above and below the plane in which the other four atoms are found.
by chrisleung-2J
Tue Dec 03, 2019 10:51 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 2
Views: 38

Re: Coordination Number

I believe that the coordination number only includes the number of ligands bonded to the central atom
by chrisleung-2J
Mon Dec 02, 2019 2:22 am
Forum: Conjugate Acids & Bases
Topic: Conjugate vs Bronsted acids/bases
Replies: 4
Views: 55

Re: Conjugate vs Bronsted acids/bases

"Bronsted Acids & Bases" refers to acids and bases according to the Bronsted-Lowry definition, which states that any compound that can donate a proton to another is considered an "acid" and any compound that can accept a proton from another is considered a "base." C...
by chrisleung-2J
Mon Dec 02, 2019 2:20 am
Forum: Conjugate Acids & Bases
Topic: 6A.3
Replies: 2
Views: 59

Re: 6A.3

I believe that "proton transfer equilibria" refers to the fact that the conjugate acid has one more proton than the conjugate base, and since all these species are present in aqueous solutions we would include H2O/H3O+ in the equation as well.
by chrisleung-2J
Mon Dec 02, 2019 2:14 am
Forum: *Molecular Orbital Theory Applied To Transition Metals
Topic: naming
Replies: 1
Views: 104

Re: naming

I believe this refers to the naming conventions used for coordination compounds, such as the order of words in the name, prefixes, etc.
by chrisleung-2J
Mon Dec 02, 2019 2:13 am
Forum: Administrative Questions and Class Announcements
Topic: Curving in Chem 14A
Replies: 7
Views: 236

Re: Curving in Chem 14A

I believe that final grades are sometimes curved depending on the distribution for the class overall, but I don't think Professor Lavelle has confirmed anything.
by chrisleung-2J
Mon Dec 02, 2019 2:12 am
Forum: Administrative Questions and Class Announcements
Topic: Calculators on Final
Replies: 6
Views: 83

Re: Calculators on Final

I believe that the Final will be more like the Midterm in terms of the style, and that most likely calculator will be necessary.
by chrisleung-2J
Fri Nov 22, 2019 3:49 pm
Forum: Ionic & Covalent Bonds
Topic: Direction in anions increase in polarizability
Replies: 3
Views: 143

Re: Direction in anions increase in polarizability

The trend for increasing polarizing power for cations would be decreasing size and increasing charge, which is why Al+3 is a common example for a cation with very strong polarizing power. On the other hand, the trend for anions would be increasing polarizability moving down and to the right.
by chrisleung-2J
Fri Nov 22, 2019 3:47 pm
Forum: Hybridization
Topic: Homework 2.45
Replies: 1
Views: 41

Re: Homework 2.45

I think what the textbook was getting at was the fact that each lone pair counts as a region of electron density and therefore contributes to hybridization. For example, in NH3, the central N atom has a hybridization of sp3 because of this.
by chrisleung-2J
Fri Nov 22, 2019 3:45 pm
Forum: Lewis Structures
Topic: Cis- vs Trans- bonds
Replies: 5
Views: 98

Re: Cis- vs Trans- bonds

In addition, the Cis- and Trans- forms of molecules are able to exist when there is a double bond present between two atoms, separating each side of the molecule, due to each form having a distinct structure since the molecule cannot rotate about the central bond (usually a C=C bond).
by chrisleung-2J
Fri Nov 22, 2019 3:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Acids
Replies: 6
Views: 74

Re: Acids

A strong acid or base is one which readily dissociates completely in water, and common examples include HCl and NaOH. Weak acids or bases only partially dissociated in water and a majority of the molecule will remain in its associated form when placed in water.
by chrisleung-2J
Fri Nov 22, 2019 12:27 am
Forum: Determining Molecular Shape (VSEPR)
Topic: name?
Replies: 4
Views: 57

Re: name?

Yes, they are two names for the same geometry, for molecules with configuration AX2E or AX3E
by chrisleung-2J
Sat Nov 16, 2019 6:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion
Replies: 3
Views: 49

Re: Repulsion

I believe that the only types of repulsions that matter thus far are the ones between regions of electrons about the central atom, as in between bonds and lone pairs.
by chrisleung-2J
Sat Nov 16, 2019 6:05 pm
Forum: Octet Exceptions
Topic: Octet expansion
Replies: 6
Views: 179

Re: Octet expansion

We haven't explicitly learned this yet, but octet expansion can only result when electrons have additional orbitals to fill at a given principal energy level. The most common form of octet expansion occurs when atoms have their valence electron in the 3rd principal level or higher and are able to fo...
by chrisleung-2J
Sat Nov 16, 2019 6:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 8
Views: 84

Re: Bond Angles

^This is true. You can't really calculate the bond angles, they must be measured in a lab.
by chrisleung-2J
Thu Nov 14, 2019 10:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T-shaped vs Trigonal Bipyramidal
Replies: 2
Views: 38

Re: T-shaped vs Trigonal Bipyramidal

Trigonal bipyramidal refers to a molecule with electrons in five bonding locations about the central atom, while T-Shaped is a derivative of Trigonal Bipyramidal in which there are 3 bonded electron pairs and 2 lone pairs about the central atom
by chrisleung-2J
Thu Nov 14, 2019 10:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E1 - Molecules with bent geometry
Replies: 7
Views: 77

Re: 2E1 - Molecules with bent geometry

Yes, although most molecules in which the central atom has lone pairs of electrons have a dipole moment, there are some exceptions in which the dipole moments caused by the lone pairs of electrons cancel out. One example of this is the configuration AX2E3, which is linear due to the three lone pairs...
by chrisleung-2J
Sun Nov 10, 2019 9:40 pm
Forum: Dipole Moments
Topic: Hydrogen Bonding
Replies: 6
Views: 63

Re: Hydrogen Bonding

Covalent and Ionic bonds are intramolecular forces, meaning that they occur between atoms within a molecule. On the other hand, Van Der Waals Forces, Dipole-Dipole Forces, and Hydrogen Bonding are intermolecular forces, meaning that they occur between molecules.
by chrisleung-2J
Sun Nov 10, 2019 9:38 pm
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 4
Views: 50

Re: Hydrogen Bonds

N, O, & F can form hydrogen bonds with H, provided that the H is bonded to an N, O, or F atom which causes the H to adopt a partial positive charge.
by chrisleung-2J
Sun Nov 10, 2019 9:37 pm
Forum: Sigma & Pi Bonds
Topic: Sigma vs pi bond
Replies: 3
Views: 55

Re: Sigma vs pi bond

Sigma bonds are the first bond that forms between two atoms, while any subsequent bonds that form are classified as π bonds.
by chrisleung-2J
Sun Nov 10, 2019 9:34 pm
Forum: Dipole Moments
Topic: London Interaction
Replies: 4
Views: 41

Re: London Interaction

London Dispersion Forces result from Induced Dipole-Induced Dipole, during which electrons on two nearby atoms of different molecules are temporarily located in a given portion of the atom causing that atom to adopt a temporary positive or negative charge, with this positive or negative charge leadi...
by chrisleung-2J
Tue Nov 05, 2019 2:13 am
Forum: Resonance Structures
Topic: Resonance Structure for 2B.15
Replies: 3
Views: 63

Resonance Structure for 2B.15

Question 2B.15 asks for the Lewis structures of the resonance hybrid ClNO2, and I understand how to find each structure. However, if we are simply asked for the Lewis structure on the exam, would the correct answer be

Cl
|
N = O
||
O

since we must account for formal charge?
by chrisleung-2J
Sun Nov 03, 2019 1:10 am
Forum: Sigma & Pi Bonds
Topic: What is the difference and why is it important?
Replies: 2
Views: 62

Re: What is the difference and why is it important?

Sigma bonds are always the first bonds to form between atoms, and all the successive bonds are π bonds. I don't know if we'll cover it in this course, but π bonds are important due to how they form (they result from overlapping p orbitals) and their implications for atoms which can engage in this fo...
by chrisleung-2J
Sun Nov 03, 2019 1:05 am
Forum: Dipole Moments
Topic: Definition
Replies: 5
Views: 98

Re: Definition

Dipole Moment refers to the momentary positive or negative charge which exists on an atom when the electrons are temporarily located at a given position on it. It is represented by an arrow placed between the partial positive and partial negative charges on two atoms, with the arrow pointing toward ...
by chrisleung-2J
Sun Nov 03, 2019 12:59 am
Forum: Formal Charge and Oxidation Numbers
Topic: When to calculate formal charge
Replies: 7
Views: 96

Re: When to calculate formal charge

I believe that at this level we would need to account for formal charge as we draw Lewis Structures, as formal charge allows us to determine which Lewis structure is the most correct one.
by chrisleung-2J
Sun Nov 03, 2019 12:57 am
Forum: Octet Exceptions
Topic: 2C.3
Replies: 3
Views: 69

Re: 2C.3

The structure which has the most favorable layout in terms of formal charge would be the correct one, I believe.
by chrisleung-2J
Sun Nov 03, 2019 12:56 am
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds question
Replies: 3
Views: 74

Re: sigma and pi bonds question

I don't believe we're going that in-depth into bonding, as we've only briefly touched upon the basics of this content, and I don't believe it will be on the midterm.
by chrisleung-2J
Sat Oct 26, 2019 8:18 pm
Forum: Resonance Structures
Topic: Expanded valence shells
Replies: 3
Views: 81

Re: Expanded valence shells

It's not just P, S, and Cl that can exist with expanded valence shells. I believe that any element which has its valence electrons in the 3rd principal level or higher can accommodate more than 8 electrons, as it gains access to d-orbitals which first exist at the 3rd principal level and can be fill...
by chrisleung-2J
Sat Oct 26, 2019 8:16 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 3
Views: 44

Re: Electron Configuration

You should always write the electron configuration in numerical order, with lower principal levels preceding higher ones.
by chrisleung-2J
Sat Oct 26, 2019 8:15 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework Problem 1E.13
Replies: 3
Views: 68

Re: Homework Problem 1E.13

The f-block is included in the configuration because f-orbitals first exist in the 4th principal level and begin filling after the 6s sublevel. The f-orbitals are those present throughout the Lanthanide and Actinide series, the two bars that are often placed below the period table on most periodic t...
by chrisleung-2J
Sat Oct 26, 2019 8:11 pm
Forum: Lewis Structures
Topic: Triple bonds
Replies: 1
Views: 34

Re: Triple bonds

I believe that this is just uncommon due to the fact that there aren't many that have a situation in which the triple bond would need to exist in multiple locations. In order for this to be possible, the central atom would need to have two or more double bonds already formed with other atoms in the ...
by chrisleung-2J
Sat Oct 26, 2019 8:04 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Factors In Multi-Electron Energy
Replies: 1
Views: 49

Re: Factors of Multi-Electron Energy

I believe that's everything!
by chrisleung-2J
Sat Oct 26, 2019 7:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 1
Views: 53

Re: Electron Configuration

You can determine electron configuration based on the position of the element in question on the periodic table. The period (horizontal row) indicates the principal energy level of the valence electrons for that element, and the groups (vertical columns) reveal the sublevel in which the valence elec...
by chrisleung-2J
Sat Oct 26, 2019 7:30 pm
Forum: Ionic & Covalent Bonds
Topic: Cation
Replies: 23
Views: 456

Re: Cation

Cations are ions with a positive charge, and can exist when atoms lose electrons. On the other hand, anions are ions with a negative charge, and can be formed when atoms lose electrons. They are probably most important to understand in the context of ionic bonds, which form between anions and cations.
by chrisleung-2J
Sat Oct 26, 2019 6:12 pm
Forum: Ionic & Covalent Bonds
Topic: Does the Octet Rule apply to Boron?
Replies: 14
Views: 146

Re: Does the Octet Rule apply to Boron?

Al can also violate the octet rule by having only 6 electrons.
by chrisleung-2J
Sat Oct 26, 2019 6:11 pm
Forum: Trends in The Periodic Table
Topic: Ionization energy
Replies: 12
Views: 199

Re: Ionization energy

I'm not sure if we'll get into it during this course, but there are some exceptions to the general trend. For example, the elements in group 16 tend to have lower 1st ionization energies than the elements in group 15 due to the fact that group 16 elements have a filled orbital which leads to greater...
by chrisleung-2J
Sat Oct 26, 2019 6:04 pm
Forum: Ionic & Covalent Bonds
Topic: Resonance (all bonds are a hybrid of different bonds)
Replies: 10
Views: 145

Re: Resonance (all bonds are a hybrid of different bonds)

If there are multiple structures with the same formal charges for each atom, I believe that you would draw all of the possible structures and put the two-headed arrow between them to indicate they're all equally possible.

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