Search found 115 matches

by Janet Nguy 2C
Tue Mar 17, 2020 6:16 pm
Forum: General Rate Laws
Topic: Knowing the rate of absorption
Replies: 3
Views: 22

Re: Knowing the rate of absorption

Refer to the Unique Rate in a chemical equation and it'll tell you how the rate of absorption for a reactant is related to the rate of formation of the product. It all depends on the stoichiometric coefficient.
by Janet Nguy 2C
Tue Mar 17, 2020 6:12 pm
Forum: Student Social/Study Group
Topic: Mental Health
Replies: 2
Views: 68

Re: Mental Health

We love to see it. Thank you for the reminder, take care!
by Janet Nguy 2C
Tue Mar 17, 2020 6:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Grading
Replies: 3
Views: 41

Re: Grading

Chem_Mod wrote:Class average will be high …
:-)


does this mean that less students will receive an A...?
by Janet Nguy 2C
Tue Mar 17, 2020 6:09 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: 4
Views: 27

Re: Microstates

Like what was said, degeneracy is related to microstates by the equation W = X^n; this is just because degeneracy describes all of the possible positions that a particle can exist in, so intuitively you would take the # of microstates to the power of the # of particles there are.
by Janet Nguy 2C
Tue Mar 17, 2020 6:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Grades
Replies: 6
Views: 70

Re: Final Grades

Since the final was multiple choice and all online, my guess is that it won't take too long to input grades.
by Janet Nguy 2C
Tue Mar 10, 2020 4:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemistry 14B Final
Replies: 9
Views: 125

Re: Chemistry 14B Final

I am also curious :')
by Janet Nguy 2C
Tue Mar 10, 2020 12:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Coronavirus Concern
Replies: 6
Views: 137

Coronavirus Concern

Hey everyone, Some other students and I are getting a little worried about the coronavirus and its spread. I myself am a little uncomfortable attending classes/attending all of these chem final review sessions. I'm especially uncomfortable because all of these rooms where the review sessions are hap...
by Janet Nguy 2C
Sun Mar 08, 2020 8:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Vertical lines vs commas
Replies: 7
Views: 19

Re: Vertical lines vs commas

Vertical lines in cell diagram represent a change in phase (if there's double vertical lines, then it indicates the presence of a salt bridge). Commas separate two species of the same phase, most of the time this will be ions in aqueous solution.
by Janet Nguy 2C
Sun Mar 08, 2020 8:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 10
Views: 27

Re: Platinum

You add platinum or another inert electrode when you don't have a solid electrode in the cell diagram.
by Janet Nguy 2C
Sat Mar 07, 2020 1:12 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert electrode
Replies: 9
Views: 52

Re: Inert electrode

Whenever you don't have any physical solid electrode you will add Pt or some other inert electrode.
by Janet Nguy 2C
Sat Mar 07, 2020 1:09 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining the cathode/anode
Replies: 9
Views: 69

Re: Determining the cathode/anode

The total Ecell should always be positive (unless the cell was powered by some non-spontaneous energy source). So if you have the standard E values for the half reactions (both in reduction form) you should flip the one that makes the total Ecell the most positive. The flipped half reaction is the o...
by Janet Nguy 2C
Tue Mar 03, 2020 11:33 am
Forum: Administrative Questions and Class Announcements
Topic: Solutions Manual Errors
Replies: 6
Views: 47

Solutions Manual Errors

I'm aware that Lavelle has a solutions manual errors page on his website. But I'm having a hard time believing that those are the only errors in the textbook... I've been seeing a lot of Chem Community posts on homework recently and a lot of them seem to point to several more errors in the solutions...
by Janet Nguy 2C
Sat Feb 29, 2020 4:15 pm
Forum: General Rate Laws
Topic: Rate Constant Units
Replies: 3
Views: 48

Rate Constant Units

How do you determine the units for the rate constant k?
The book says it changes if dealing with zeroth, first, or second order reactions, but why is this, and how can you tell?
by Janet Nguy 2C
Sat Feb 29, 2020 4:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt in cell diagrams
Replies: 3
Views: 20

Re: Pt in cell diagrams

Pt is kind of like an inert metal (you can think of it that way); it acts literally as a solid metal to be the physical electrode for the sides of the battery that don't already have a solid metal to do this.

Pt is used in cell diagrams if there's no solid metal in either the anode or cathode.
by Janet Nguy 2C
Sat Feb 29, 2020 4:03 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 3
Views: 26

Re: Balancing Redox Reactions

Here is a general flowchart for balancing redox reactions in acidic/basic solution: Both types of situations start the same way: 1. determine the oxidation and reduction half reactions. 2. Balance both half reactions: a) Balance elements other than H or O b) Balance O elements by adding H2O molecule...
by Janet Nguy 2C
Mon Feb 17, 2020 1:12 pm
Forum: Balancing Redox Reactions
Topic: Same Molecule as Both Reducing and Oxidizing Agent
Replies: 1
Views: 30

Same Molecule as Both Reducing and Oxidizing Agent

For 6K3 part d, it states that for the reaction,
Cl2 (g) ---> HClO (aq) + Cl2 (g)
Cl2 is both the oxidizing AND reducing agent. How can this be? Can someone explain what the half reactions would look like?
by Janet Nguy 2C
Sun Feb 16, 2020 8:49 pm
Forum: Balancing Redox Reactions
Topic: 6K5 part a (check my work?)
Replies: 1
Views: 42

6K5 part a (check my work?)

6K.5 Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction. a) O3 (aq) + Br- (aq) ---> O2 (g) + BrO3- (aq) Here is my work, I'm not sure if I d...
by Janet Nguy 2C
Sun Feb 16, 2020 8:07 pm
Forum: Balancing Redox Reactions
Topic: 6K3. part d
Replies: 1
Views: 22

6K3. part d

6K.3 Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in acidic solution. Identify the oxidizing agent and reducing agent in each reaction. d) Cl2 (g) --> HClO (aq) + Cl2 (g) What would the oxidation and reduction half rea...
by Janet Nguy 2C
Sun Feb 16, 2020 7:33 pm
Forum: Balancing Redox Reactions
Topic: Oxygen and Hydrogen
Replies: 4
Views: 24

Oxygen and Hydrogen

In the context of oxidation number:

Is Oxygen always 2- ?
Is Hydrogen always 1+ ?
Is it safe to assume that Oxygen and Hydrogen won't ever oxidize or reduce in a redox reaction?
by Janet Nguy 2C
Sun Feb 16, 2020 6:47 pm
Forum: Balancing Redox Reactions
Topic: Identifying Elements Undergoing Oxidation/Reduction
Replies: 5
Views: 23

Re: Identifying Elements Undergoing Oxidation/Reduction

You can also look at the element's oxidation number before and after the equation. Elements whose oxidation number increases are oxidized, and vice versa for reduced. For 6K1: Given H is typically +1 oxidation and oxygen is typically -2 oxidation number, we can tell that our two elements undergoing...
by Janet Nguy 2C
Sun Feb 16, 2020 6:34 pm
Forum: Balancing Redox Reactions
Topic: easier to split?
Replies: 6
Views: 33

Re: easier to split?

Because his example occurred under acidic conditions, the redox reaction becomes more complicated as ions from the aqueous solutions will interact with each other. This is why he separates them into 2 half-reactions, one for the oxidation reaction and one for the reduction reaction.
by Janet Nguy 2C
Sun Feb 16, 2020 6:32 pm
Forum: Balancing Redox Reactions
Topic: Identifying Elements Undergoing Oxidation/Reduction
Replies: 5
Views: 23

Identifying Elements Undergoing Oxidation/Reduction

How do you identify elements that undergo oxidation/reduction in a reaction? For example, in 6K1 part a, it asks: Identify elements undergoing oxidation/reduction and indicate their initial and final oxidation numbers for the equation H+ (aq) + Cr2O7 [2-] (aq) + C2H5OH (aq) -> Cr [3+] (aq) + C2H4O (...
by Janet Nguy 2C
Sun Feb 16, 2020 2:12 pm
Forum: Balancing Redox Reactions
Topic: oxidation vs reduction
Replies: 19
Views: 105

Re: oxidation vs reduction

How do you determine an elements oxidation number ? There's a few general rules for this: For any element, oxidation number is 0. (ex: He, O2) Oxygen is usually 2- Hydrogen is usually 1+ All charges must add up to the overall charge of the molecule (ex: for the MnO4- ion, the oxidation number for O...
by Janet Nguy 2C
Sun Feb 16, 2020 2:09 pm
Forum: Balancing Redox Reactions
Topic: oxidation vs reduction
Replies: 19
Views: 105

Re: oxidation vs reduction

You can think about reduction as a reduction of positive charge. (gain of electrons)
Oxidation would be adding positive charge. (losing electrons)
by Janet Nguy 2C
Sun Feb 16, 2020 1:33 pm
Forum: Administrative Questions and Class Announcements
Topic: about the Midterm...
Replies: 8
Views: 108

about the Midterm...

I feel a little lost. I felt like I had a decent understanding of the concepts for the midterm, and I could provide an answer to every statement on the learning outcome outlines. I went to Step-Ups weekly, I did the homework, I went to multiple review sessions, and I made sure I could do every Pizza...
by Janet Nguy 2C
Wed Feb 12, 2020 2:25 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Isochoric = Irreversible?
Replies: 2
Views: 46

Re: Isochoric = Irreversible?

Typo, sorry! i meant Isobaric.
by Janet Nguy 2C
Wed Feb 12, 2020 2:12 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Isochoric = Irreversible?
Replies: 2
Views: 46

Isochoric = Irreversible?

So my understanding of the different work equations is this: \small w=-p\Delta V for a system at constant pressure, i.e. isochoric process. \small w=-nRT\ln (\frac{V2}{V1}) for a reversible process not at constant pressure. So does isochoric necessarily mean that the system is undergoing an ...
by Janet Nguy 2C
Wed Feb 12, 2020 2:04 pm
Forum: Calculating Work of Expansion
Topic: work in reversible reaction
Replies: 4
Views: 49

Re: work in reversible reaction

dV is a way of representing change in volume (this would be dV, the derivative of V, like you said). V2 and V1 represent the final and initial volumes, respectively. They do not represent microstates; I think you are confusing w (work) with W (degeneracy).
by Janet Nguy 2C
Tue Feb 11, 2020 5:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Pizza Rolls REVIEW Session DOWNLOAD HERE
Replies: 67
Views: 2476

Re: Pizza Rolls REVIEW Session DOWNLOAD HERE

for number 7 I understand how to solve for q but how do you solve for w with so many missing variables from the pv=nrt equation? The general equation for work is w=-p\Delta V at a constant pressure. Because we are given the \Delta H value, we can assume that the reaction occurred under constant pre...
by Janet Nguy 2C
Tue Feb 11, 2020 5:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Pizza Rolls REVIEW Session DOWNLOAD HERE
Replies: 67
Views: 2476

Re: Pizza Rolls REVIEW Session DOWNLOAD HERE

For question 10 (25.0g ice at 0.00 Celcius dropped into 265 mL of water at 25.0 Celcius. What is Tf of the water?): Why can we assume that all 25 grams of ice melted into water? i.e. why is the m1 (mass for the ice undergoing phase change) equal to the m2 (mass of the ice that becomes water)? How do...
by Janet Nguy 2C
Sat Feb 08, 2020 1:07 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Equation for Cv and Cp
Replies: 3
Views: 28

Re: Equation for Cv and Cp

For diatomic molecules, Cv = 5/2R and Cp = 7/2R. I'm not sure about the other kind, though. But I don't think we would be asked something that's not monatomic or diatomic.
by Janet Nguy 2C
Tue Feb 04, 2020 10:08 pm
Forum: Calculating Work of Expansion
Topic: When to use different R values
Replies: 2
Views: 14

When to use different R values

So R = 8.3145 and R = 0.08206
Under what circumstances would we have to differentiate between these two values when problem solving? How do we know when to use either constant?
by Janet Nguy 2C
Tue Feb 04, 2020 8:49 pm
Forum: Calculating Work of Expansion
Topic: Isobaric Processes
Replies: 1
Views: 20

Isobaric Processes

If the pressure of a system is constant, how can the volume be changing? isn't volume proportional to pressure?
by Janet Nguy 2C
Tue Feb 04, 2020 8:20 pm
Forum: Calculating Work of Expansion
Topic: Isothermic Processes
Replies: 1
Views: 16

Isothermic Processes

If , then why in an isothermic processes is q = w? Shouldn't q = -w?

Does this have to do with whether or not it's work of expansion or work of compression?
by Janet Nguy 2C
Sun Feb 02, 2020 9:46 pm
Forum: Phase Changes & Related Calculations
Topic: Relevance of Phase Changes
Replies: 9
Views: 48

Re: Relevance of Phase Changes

Since the enthalpy value changes when a substances changes phases, it is necessary to calculate separately the phase change enthalpy and add it to the same-phase reaction enthalpy.
by Janet Nguy 2C
Sun Feb 02, 2020 9:41 pm
Forum: Administrative Questions and Class Announcements
Topic: HW 5
Replies: 3
Views: 22

Re: HW 5

I'd say you would be allowed to use Thermochemistry topics, but I would focus more heavily on Thermodynamics because we'll be learning that this week.
by Janet Nguy 2C
Sun Feb 02, 2020 9:38 pm
Forum: Administrative Questions and Class Announcements
Topic: slides
Replies: 8
Views: 66

Re: slides

Dr. Lavelle does not post his slides or lectures, but he has full video lectures of the Equilibrium topic on his website. But that is the only one he offers.
by Janet Nguy 2C
Sun Feb 02, 2020 9:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess’ Law
Replies: 10
Views: 53

Re: Hess’ Law

To add on to what everyone said above, Hess's law can be useful for finding the total enthalpy for a reaction if you are given multiple sub-reactions. You then manipulate all the sub-reactions to obtain the one they ask for, and then calculate the total enthalpy by adding all the enthalpies of the s...
by Janet Nguy 2C
Sun Feb 02, 2020 9:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm dates
Replies: 11
Views: 50

Re: Midterm dates

The midterm will be cumulative. Specifically, Dr. Lavelle says that the midterm will cover Equilibrium, Acids & Bases, Thermochemistry, and Thermodynamicsm.
by Janet Nguy 2C
Sun Feb 02, 2020 9:35 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 3
Views: 33

Re: Phase changes

You need to account for phase changes in enthalpy problems because the value will be different when the phase changes. This is why you need to calculate separately the enthalpy change from different phases and then add together the enthalpy change from the same phase reaction.
by Janet Nguy 2C
Sun Feb 02, 2020 9:32 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy
Replies: 7
Views: 32

Re: Enthalpy

q = enthalpy when the pressure is constant, such as in an open system.
by Janet Nguy 2C
Mon Jan 20, 2020 7:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: parts of salts that don't affect pH
Replies: 4
Views: 28

parts of salts that don't affect pH

Which parts of salts aren't included in the equilibrium concentration? I know that Na+ and Cl- don't affect the pH because they are stable in aqueous solution, but what other cations/anions should I know about?
by Janet Nguy 2C
Mon Jan 20, 2020 4:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: "Quick Way" for predicting response to changes in volume/pressure
Replies: 3
Views: 23

"Quick Way" for predicting response to changes in volume/pressure

Hi guys, Dr. Lavelle summarized the 'quick way' for predicting the response of chemical equilibria to changes in volume as follows: -if you decrease the volume and there's more moles of gas on the left, then the reaction shifts right. -if you decrease the volume and there's more moles of gas on the ...
by Janet Nguy 2C
Mon Jan 20, 2020 3:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Salt Solutions
Replies: 3
Views: 39

Salt Solutions

First of all, what exactly is a salt and how can you identify it within a reaction?

Secondly, how is calculating the pH of a salt solution going to be different than calculating the pH of acid/base solutions?
by Janet Nguy 2C
Sun Jan 19, 2020 9:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exo/Endo-thermic Rxns
Replies: 5
Views: 26

Re: Exo/Endo-thermic Rxns

If the topic of exothermic/endothermic reactions were to come up in a test question, it would probably either tell you explicitly if the reaction was exo/endothermic OR it'll give you the delta H value (aka change in enthalpy), and from there you could decide if it was exothermic or endothermic. If ...
by Janet Nguy 2C
Sun Jan 19, 2020 9:08 pm
Forum: General Science Questions
Topic: Acids
Replies: 3
Views: 23

Re: Acids

Lewis Acids: acids are electron acceptors, bases are electron donors.
Bronsted-Lowry: acids are proton donors, bases are proton acceptors.
by Janet Nguy 2C
Sun Jan 19, 2020 9:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Q
Replies: 14
Views: 51

Re: K vs Q

Q is calculated the same way as K, but Q is used to calculate the compositions for reactants and products at ANY TIME during the reaction, not just at equilibrium. You can compare Q to K to see if the reaction is at equilibrium, shifted to the left, or shifted to the right.
by Janet Nguy 2C
Sun Jan 19, 2020 9:00 pm
Forum: Ideal Gases
Topic: When to use PV=nRT
Replies: 5
Views: 35

Re: When to use PV=nRT

pV = nRT is used to convert between concentrations and partial pressures. Basically it means that you can express K for gases as either their molar concentrations or their partial pressures.
by Janet Nguy 2C
Sun Jan 19, 2020 8:57 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic vs. endothermic
Replies: 2
Views: 14

Re: Exothermic vs. endothermic

An endothermic reaction requires heat while forming product, so heating would favor product formation.
You can think about this as R + heat -> P

An exothermic reaction gives off heat while forming product, so heating would favor reactant formation.
You can think about this as R -> P + heat
by Janet Nguy 2C
Sun Jan 19, 2020 8:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Use of buffers
Replies: 2
Views: 18

Re: Use of buffers

A buffer is a solution that resists a change of pH because it contains both an acid and its conjugate base (or a base and its conjugate acid). It's especially helpful in biological situations (for example, the blood needs to maintain a pH of about 7.4 otherwise it will lose the ability to perform ma...
by Janet Nguy 2C
Sun Jan 19, 2020 7:21 pm
Forum: Ideal Gases
Topic: homework #3
Replies: 16
Views: 133

Re: homework #3

Usually we're supposed to do HW problems based on what we learned in that week, so I would focus on Acid-Base Equilibria
by Janet Nguy 2C
Sun Jan 19, 2020 6:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Conjugate Seesaw
Replies: 5
Views: 29

Re: Conjugate Seesaw

The Conjugate Seesaw is basically is the term for the following phenomenon: -The stronger an acid, the weaker its conjugate base -The stronger a base, the weaker its conjugate acid This is kind of intuitive, because it comes from the equation Ka x Kb = Kw, where Kw is a constant (1.0 * 10^-14) at 25...
by Janet Nguy 2C
Sun Jan 19, 2020 3:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6B. 3
Replies: 2
Views: 32

6B. 3

6B.3 A careless laboratory technician wants to prepare 200.0 mL of a 0.025 m HCl(aq) solution but uses a volumetric flask of vol- ume 250.0 mL by mistake. (a) What would the pH of the desired solution have been? (b) What will be the actual pH of the solution as prepared? I did this problem but I don...
by Janet Nguy 2C
Wed Jan 15, 2020 11:38 am
Forum: Administrative Questions and Class Announcements
Topic: Test 1 Topics
Replies: 4
Views: 46

Test 1 Topics

Hi!
I know test 1 is coming up next week; what topics/what kind of questions should I be prepared for? And to what extent are acids/bases going to be on the test?
by Janet Nguy 2C
Sun Jan 12, 2020 1:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I. 19
Replies: 3
Views: 23

5I. 19

Hello! for question 5I19, how do you go about incorporating the "60% of H2 reacted at equilibrium" in the calculations for K? Here is the full problem: 5I.19 A reaction mixture that consisted of 0.400 mol H2 and 1.60 mol I2 was introduced into a flask of volume 3.00 L and heated. At equili...
by Janet Nguy 2C
Sun Jan 12, 2020 12:36 pm
Forum: Ideal Gases
Topic: Bars vs atmospheres
Replies: 13
Views: 52

Re: Bars vs atmospheres

I believe that both are used because they are both units of pressure.
by Janet Nguy 2C
Fri Jan 10, 2020 12:38 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and relation of [R] to [P]
Replies: 5
Views: 47

Re: Q and relation of [R] to [P]

For Q<K, why is [R]>[P] and for Q>K, why is [P]>[R]? If Q is less than K, this implies that the reaction is proceeding in the forward direction, where reactants are being transformed into products. This means that there will be a higher concentration of reactants to products. If Q is greater than K...
by Janet Nguy 2C
Thu Jan 09, 2020 9:46 pm
Forum: Ideal Gases
Topic: eq constant
Replies: 4
Views: 25

Re: eq constant

My TA said that the activity of solids and liquids are essentially equal to 1, so when calculating the equilibrium constant solids and liquids do not matter because all the units are essentially dealing with the activity of a species.
by Janet Nguy 2C
Thu Jan 09, 2020 8:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Catalysts
Replies: 7
Views: 40

Catalysts

Can someone define a catalyst with examples and explain how it affects a reaction?
by Janet Nguy 2C
Thu Jan 09, 2020 8:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Clarification on equilibrium
Replies: 3
Views: 20

Re: Clarification on equilibrium

"Favoring" a side just means that the reaction either has a higher concentration of reactants or products. If a reaction "favors" the left, then it favors reactants; if a reaction "favors" the right, then there will be more product at equilibrium.
by Janet Nguy 2C
Fri Dec 06, 2019 2:05 am
Forum: Polyprotic Acids & Bases
Topic: Electron withdrawing
Replies: 1
Views: 24

Re: Electron withdrawing

When you have multiple highly electronegative atoms bonded to a central atom in the resulting anion of an acid-base reaction, the electronegative atoms will pull electron density towards it, thereby diffusing the negative charge across the entire molecule and thus making it more stable. This "e...
by Janet Nguy 2C
Tue Dec 03, 2019 5:07 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra
Replies: 3
Views: 57

Re: Atomic Spectra

Just to add on, here is something to remember when doing these kinds of calculations:

The change in energy will be POSITIVE if the electron jumps from a lower energy to a higher energy.
The change in energy will be NEGATIVE if the electron jumps from a higher energy to a lower energy.
by Janet Nguy 2C
Tue Dec 03, 2019 5:03 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Where to minimize formal charge
Replies: 4
Views: 48

Re: Where to minimize formal charge

If you absolutely can't have zero formal charge, be sure to put the negative charge on the most electronegative atom and the positive charge on the most electropositive atoms. Usually if you see Oxygen it will have a negative formal charge because typically it is more electronegative than other atoms.
by Janet Nguy 2C
Tue Dec 03, 2019 11:58 am
Forum: Bond Lengths & Energies
Topic: Boiling Point and bonds
Replies: 5
Views: 59

Re: Boiling Point and bonds

For LDFs, the higher molecular weight results in a higher boiling point (ie HI has a higher boiling point than HCl) For dipole-dipole interactions, the greater difference in electronegativity has a higher boiling point Why does a higher molecular weight result in a higher boiling point? And why doe...
by Janet Nguy 2C
Tue Dec 03, 2019 11:55 am
Forum: Naming
Topic: Iron vs Ferrate
Replies: 5
Views: 32

Re: Iron vs Ferrate

Hi! If the iron in the compound has a negative charge/is an anion then it will be ferrate. Any other time it’ll be iron.
by Janet Nguy 2C
Tue Dec 03, 2019 11:53 am
Forum: Amphoteric Compounds
Topic: Amphoteric, Amphiprotic, Polyprotic
Replies: 2
Views: 50

Amphoteric, Amphiprotic, Polyprotic

Hi! On the marshmallow review it asks us to determine if a molecule is amphoteric, ionic, amphiprotic and/or polyprotic.

Can someone define the difference between all of these and outline how to determine each condition? Thanks!
by Janet Nguy 2C
Sun Dec 01, 2019 9:48 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 5
Views: 43

Re: Polydentate

Andrew Pfeiffer 1J wrote:The molecule in question is a polydentate when

a.) the ligand has at least 2 molecules that have lone pairs and

b.) the atoms have a geometry that enables the transition metal cation to be bound in more than one place at the same time.


what kind of geometries would allow for this?
by Janet Nguy 2C
Sun Dec 01, 2019 9:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 6
Views: 28

Re: Strong Acids

This has to do with the bond length as the longer the bond, the more easily it is broken. This means that if the bond is longer, then it would be considered a stronger acid in comparisons such as HF and HI as in this case HI bond is longer making it easier to lose the H+. How do you tell if it has ...
by Janet Nguy 2C
Sun Dec 01, 2019 9:00 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 6
Views: 28

Re: Strong Acids

This has to do with the bond length as the longer the bond, the more easily it is broken. This means that if the bond is longer, then it would be considered a stronger acid in comparisons such as HF and HI as in this case HI bond is longer making it easier to lose the H+. How do you tell if it has ...
by Janet Nguy 2C
Sun Dec 01, 2019 9:00 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 6
Views: 28

Re: Strong Acids

This has to do with the bond length as the longer the bond, the more easily it is broken. This means that if the bond is longer, then it would be considered a stronger acid in comparisons such as HF and HI as in this case HI bond is longer making it easier to lose the H+. How do you tell if it has ...
by Janet Nguy 2C
Sun Dec 01, 2019 8:41 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 9C.5
Replies: 2
Views: 27

Re: HW 9C.5

Thank you so much, that was very helpful!

Does anyone have an explanation for when you deal with resonance?
by Janet Nguy 2C
Sun Dec 01, 2019 5:00 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 9C.7
Replies: 1
Views: 24

HW 9C.7

9C.7 Which of the following isomers of diaminobenzene can form chelating complexes? Explain your reasoning. I couldn't attach the pictures of the isomers here, sorry! Can someone explain to me what it means for a compound to be "chelating," and how to determine what kinds of compounds can ...
by Janet Nguy 2C
Sun Dec 01, 2019 4:56 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 9C.5
Replies: 2
Views: 27

HW 9C.5

Hi! Problem 9C.5 on the homework is this: Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2CH2NH2)2; (b) CO3 22; (c) H2O; (d) oxalate. Can someone expl...
by Janet Nguy 2C
Sat Nov 30, 2019 6:31 pm
Forum: Naming
Topic: Ligands
Replies: 6
Views: 55

Ligands

How do you know just by looking at a coordination compound that the ligand attached to the TM atom is neutral or has a charge? Or are we just supposed to memorize the list of ligands that Dr. Lavelle sent us?
by Janet Nguy 2C
Sat Nov 30, 2019 12:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: When VSEPR doesn't work
Replies: 4
Views: 45

When VSEPR doesn't work

When is VSEPR theory not helpful in determining shape? I know it works well for certain elements but not others. Why?
by Janet Nguy 2C
Thu Nov 21, 2019 6:17 pm
Forum: General Science Questions
Topic: Test 2: IMF
Replies: 4
Views: 87

Re: Test 2: IMF

You might also need to know how IMF relate to relative boiling points of molecules.
by Janet Nguy 2C
Thu Nov 21, 2019 6:12 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: Strongest force
Replies: 6
Views: 40

Re: Strongest force

I agree with everyone before me, but to add on: Hydrogen-bonding is the third strongest intermolecular force because when Hydrogen reacts with a highly electronegative atom (N, O, F) it will act as a very strong dipole and will be stronger than the average dipole-dipole interaction.
by Janet Nguy 2C
Thu Nov 21, 2019 6:09 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: in need of test 2 practice problems
Replies: 5
Views: 76

Re: in need of test 2 practice problems

I would practice drawing Lewis structures as you will need to have those mastered in order to do the VSEPR questions.
by Janet Nguy 2C
Thu Nov 21, 2019 6:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Class Next Wednesday?
Replies: 3
Views: 66

Re: Class Next Wednesday?

There will be class next Wednesday because we're a little behind due to the fires.
by Janet Nguy 2C
Thu Nov 21, 2019 6:01 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds
Replies: 3
Views: 29

Re: sigma and pi bonds

If you see a single bond, it will be a sigma bond. Pi bonds occur whenever there's a p-orbital interacting with another p-orbital, so when there's a double bond, one will be a pi bond and the other will be a sigma bond (because if you have 2 pi bonds the bond will break).
by Janet Nguy 2C
Thu Nov 21, 2019 5:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: XA2E2
Replies: 9
Views: 67

Re: XA2E2

Because the tetrahedral shape is unique, you can remove any 2 atoms and replace them with lone pairs and you would end up with a bent shape.
by Janet Nguy 2C
Thu Nov 21, 2019 5:55 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Hydrogen Bonding Rules
Replies: 6
Views: 62

Re: Hydrogen Bonding Rules

Each lone pair is considered a single Hydrogen bonding site; so if you have an Oxygen atom with 2 lone pairs attached to it, that would be considered two H-bonding sites.
by Janet Nguy 2C
Sat Nov 16, 2019 11:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion
Replies: 3
Views: 42

Re: Repulsion

You should know the relative repulsion strengths just in case he asks for you to comment on the bond angles of a molecule (because it most likely isn't exactly the value expected in the VSEPR model)
by Janet Nguy 2C
Sat Nov 16, 2019 10:53 pm
Forum: Bond Lengths & Energies
Topic: Quiz for Next week dashes/wedges
Replies: 11
Views: 104

Re: Quiz for Next week dashes/wedges

I don't think we will ever have to draw a diagram with dashes and wedges; we would just have to name the molecular shape. But if you were asked to do so, the wedged bond would be the bond closest to you while the dashed bond is the one behind it.
by Janet Nguy 2C
Sat Nov 16, 2019 10:48 pm
Forum: Hybridization
Topic: test 2
Replies: 8
Views: 75

Re: test 2

pauline 1L wrote:does anyone know if this test is cumulative? are we gonna be tested on some info from before the midterm

According to my TA, the test is not cumulative. We will only be tested on everything after the midterm minus hybridization and other new stuff.
by Janet Nguy 2C
Sat Nov 16, 2019 10:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar or non polar?
Replies: 7
Views: 48

Re: polar or non polar?

You can tell from the Lewis structure if a molecule is polar or nonpolar by looking at the dipole moments (which you can discern using electronegativity trends). If they cancel (meaning the dipole moments point in opposite directions) then it will be nonpolar. Additionally, a molecule will be nonpol...
by Janet Nguy 2C
Tue Nov 05, 2019 11:29 pm
Forum: Lewis Structures
Topic: Lowest Energy on Formal Charge
Replies: 3
Views: 40

Re: Lowest Energy on Formal Charge

The lowest energy lewis structure is the one with the least formal charge (i.e. closest to zero). We move bonds around so that we can achieve this; it all depends on the # of valence electrons in the element and how many electrons (shared or lone pairs) surround the element in the structure. Creati...
by Janet Nguy 2C
Tue Nov 05, 2019 11:24 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Strength of Cations
Replies: 8
Views: 56

Re: Polarizing Strength of Cations

From my understanding, a smaller ionic radius means that the electrons are pulled more closely to the positively charged nucleus. This means that a smaller cation will have more polarizing power over an anion, especially when dealing with a large anion, whose electrons will be further from the nucle...
by Janet Nguy 2C
Tue Nov 05, 2019 11:16 pm
Forum: Lewis Structures
Topic: Lowest Energy on Formal Charge
Replies: 3
Views: 40

Re: Lowest Energy on Formal Charge

The lowest energy lewis structure is the one with the least formal charge (i.e. closest to zero). We move bonds around so that we can achieve this; it all depends on the # of valence electrons in the element and how many electrons (shared or lone pairs) surround the element in the structure. Creatin...
by Janet Nguy 2C
Tue Nov 05, 2019 1:07 am
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 2
Views: 44

Re: Resonance Structures

If a question asks you to draw a resonance structure for something, assume that they mean to draw the lowest energy one. But you CAN draw resonance structures for things that aren't the lowest energy.
by Janet Nguy 2C
Sun Nov 03, 2019 2:08 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Purpose of Formal Charge
Replies: 6
Views: 32

Re: Purpose of Formal Charge

Assigning formal charge allows you to determine the most stable and accurate lewis structure for the compound. There can be multiple valid/correct ways to draw a Lewis structure for something, but the lowest energy model (which you use formal charges to find) will be a better representation of what ...
by Janet Nguy 2C
Fri Nov 01, 2019 11:23 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy (10d on Midterm Review)
Replies: 3
Views: 33

Ionization Energy (10d on Midterm Review)

10. d) Rank the following in order of increasing ionization energies: C N O F This was one of the questions on the midterm review packet: the answer is C < O < N < F, but I'm still confused on why, since I thought that ionization energy increases across a period. They mentioned that N's half-filled ...
by Janet Nguy 2C
Fri Nov 01, 2019 11:09 pm
Forum: Properties of Light
Topic: when not to use the light equation?
Replies: 4
Views: 40

Re: when not to use the light equation?

You can only use the equation c = frequency * wavelength if it's a problem dealing with light/electromagnetic radiation/photons.
by Janet Nguy 2C
Fri Nov 01, 2019 11:02 pm
Forum: Trends in The Periodic Table
Topic: Periodic Table & Formulas
Replies: 2
Views: 24

Re: Periodic Table & Formulas

I think it will be the same!
by Janet Nguy 2C
Fri Nov 01, 2019 8:26 pm
Forum: Administrative Questions and Class Announcements
Topic: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
Replies: 52
Views: 4529

Re: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]

Does anyone know if the midterm will include our most recent topics like Lewis Acids/Bases, Dipole moments, etc.? Or is the cutoff for drawing lewis structures?
by Janet Nguy 2C
Sat Oct 26, 2019 6:31 pm
Forum: Ionic & Covalent Bonds
Topic: Resonance (all bonds are a hybrid of different bonds)
Replies: 10
Views: 99

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

A better representation would be to draw the resonance hybrid (in benzene's case, it is just the hexagon with a circle in the middle to denote that the double bonds could be in either of the two positions)
by Janet Nguy 2C
Sat Oct 26, 2019 6:27 pm
Forum: Ionic & Covalent Bonds
Topic: lewis structures for diff bonds
Replies: 5
Views: 73

Re: lewis structures for diff bonds

We draw lewis structures for covalent bonds with the line to signify that they share their electrons; ionic bonds would be written with a bracket and their charge. An example of a lewis structure with an ionic bond is ammonium sulfate (NH4)2SO4 which Dr. Lavelle drew as an example last week.
by Janet Nguy 2C
Sat Oct 26, 2019 6:18 pm
Forum: Ionic & Covalent Bonds
Topic: Expanded Valence Shells
Replies: 4
Views: 47

Re: Expanded Valence Shells

The elements that are in period 3 or higher have a d orbital that can accommodate for expanded valence shells; we know this because when n=3, l can be 0,1,2 and therefore they have a d orbital that can fill more than the octet for the s&p orbitals.
by Janet Nguy 2C
Sat Oct 26, 2019 6:16 pm
Forum: Ionic & Covalent Bonds
Topic: "Delocalized" Electrons
Replies: 5
Views: 58

"Delocalized" Electrons

Can someone explain to me what it means for electrons to be "delocalized?" And why electrons are delocalized in resonance structures?
by Janet Nguy 2C
Sat Oct 26, 2019 2:12 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity and electron affinity
Replies: 3
Views: 26

Re: Electronegativity and electron affinity

I believe electronegativity is a measure of how well an atom pulls binding/shared electrons to itself, whereas electron affinity is a measure of how willing an atom is to accept an electron.

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