Search found 56 matches

by Ellen Amico 2L
Mon Jan 20, 2020 7:19 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Test 1 material
Replies: 3
Views: 23

Re: Test 1 material

I don't think so, considering it's not listed on Outline 2. If he doesn't mention it in class either I don't think it's something we need to know.
by Ellen Amico 2L
Mon Jan 20, 2020 7:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K
Replies: 5
Views: 14

Re: K

The only time K is changed is when the temperature is changed (endo/exothermic reactions). For changes in concentration or pressure, the reaction will adjust so it can eventually go back to equilibrium and therefore remain at the same K value.
by Ellen Amico 2L
Mon Jan 20, 2020 7:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Coverting Kp to Kc
Replies: 2
Views: 4

Re: Coverting Kp to Kc

It just depends on what units the data is given in. If it's concentrations, then you would denote that with Kc, but if you're given it in pressure, then denote it with Kp. If for some reason you need to convert between concentration and pressure, you can use PV=nRT.
by Ellen Amico 2L
Mon Jan 20, 2020 7:10 pm
Forum: Student Social/Study Group
Topic: Test 1
Replies: 8
Views: 33

Re: Test 1

There's no practice tests but if you do all the homework problems in the textbook and review your lecture notes you should be well prepared!
by Ellen Amico 2L
Mon Jan 20, 2020 7:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE table and X
Replies: 6
Views: 13

Re: ICE table and X

You can approximate when K is less than 10^-3 because the change in the initial concentration will be so small that x will be a negligible value.
by Ellen Amico 2L
Fri Jan 10, 2020 5:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Change in k
Replies: 11
Views: 40

Re: Change in k

Because of Le Chatelier's Principle. the reaction will adjust in order to keep the ratio of products to reactants the same. For example, if there's a higher concentration of reactants, the reaction will adjust to have a higher concentration of products. The actual concentrations will change, but the...
by Ellen Amico 2L
Fri Jan 10, 2020 5:27 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: HW 5J.5
Replies: 8
Views: 25

Re: HW 5J.5

The rule for changes in pressure applies to only moles of gas, so you don't consider the solid and therefore there are more moles of gas on the right, so the reaction shifts to the left and favors the reactants.
by Ellen Amico 2L
Fri Jan 10, 2020 5:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Alternative Forms [ENDORSED]
Replies: 2
Views: 25

Re: Alternative Forms [ENDORSED]

It just depends on what unit the the products and reactants are given in. If it's in molar concentration, then the equilibrium constant is denoted as Kc. If it's given in partial pressures, then it's denoted as Kp. They both mean the same thing, but it's just to differentiate between both.
by Ellen Amico 2L
Fri Jan 10, 2020 4:58 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Today's Lecture
Replies: 3
Views: 22

Re: Today's Lecture

The reasoning really comes from comparing Q (reaction quotient) to K. In the example he used, the concentration doubled due to the change in pressure, so Q < K and the reaction shifts right. There was more moles on the left, so this is consistent with the short reasoning. I wouldn't worry too much a...
by Ellen Amico 2L
Fri Jan 10, 2020 4:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure and Volume
Replies: 8
Views: 23

Re: Pressure and Volume

Changes in pressure or volume cause changes in concentration (due to PV=nRT), and changes in concentration don't affect K due to Le Chatelier's Principle, so that's why pressure and volume don't affect K, only temperature.
by Ellen Amico 2L
Sat Dec 07, 2019 10:40 am
Forum: Quantum Numbers and The H-Atom
Topic: Midterm Question 6A
Replies: 1
Views: 21

Midterm Question 6A

For 6A on the midterm, I thought the question was asking about the quantum number l because the question mentions subshells, but what are the correct values for this question?
by Ellen Amico 2L
Sat Dec 07, 2019 10:37 am
Forum: Photoelectric Effect
Topic: Midterm Question 2B
Replies: 2
Views: 28

Midterm Question 2B

I'm going over the midterm and I was wondering what the correct graph would look like for question 2B, and why?
by Ellen Amico 2L
Sat Dec 07, 2019 10:32 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka Kb on the Final
Replies: 2
Views: 34

Re: Ka Kb on the Final

I don't think this is something we need to know a lot about for the final. Ka and Kb were mentioned in a review session yesterday, so I would just know the formula for calculating them and know that they relate to weak acids/bases. However, I think that most of our calculations will have to do with ...
by Ellen Amico 2L
Sat Dec 07, 2019 10:30 am
Forum: Lewis Acids & Bases
Topic: About 6A.17
Replies: 1
Views: 21

Re: About 6A.17

Here's what my TA told me:
metals form basic oxides
nonmetals form acidic oxides
elements diagonally from Be to Po on periodic table and some d-block elements form amphoteric molecules.

so for example, SO2 would be acidic since S is a nonmetal.
by Ellen Amico 2L
Sat Dec 07, 2019 10:28 am
Forum: Lewis Acids & Bases
Topic: Acids and Bases Lists
Replies: 1
Views: 21

Re: Acids and Bases Lists

Yes!
Strong acids: HCl, HBr, HNO3, H2SO4, HClO4 and HI
Strong bases: oxides and hydroxides of group 1 and 2 metal cations (e.g. NaOH, CaO)
by Ellen Amico 2L
Sat Dec 07, 2019 10:25 am
Forum: Lewis Acids & Bases
Topic: formic acid
Replies: 1
Views: 16

Re: formic acid

The methyl group on acetic acid is electron donating and stabilizes the structure of the compound more, and this also destabilizes the negative charge on the conjugate base. If the conjugate base is less stable, then the corresponding acid is less acidic. Formic acid has a hydrogen attached rather t...
by Ellen Amico 2L
Sat Dec 07, 2019 10:10 am
Forum: Identifying Acidic & Basic Salts
Topic: Identifying Acidic and Basic Salts
Replies: 3
Views: 50

Re: Identifying Acidic and Basic Salts

You can also look at the ions and see if they're conjugate acids/bases of strong or weak acids/bases. For example, if the ions are the conjugate acid and base of a strong acid and a strong base, then you will know the salt is neutral.
by Ellen Amico 2L
Sat Dec 07, 2019 10:05 am
Forum: Lewis Acids & Bases
Topic: 6A.17
Replies: 1
Views: 12

Re: 6A.17

My TA told me these rules:
metals form basic oxides
nonmetals form acidic oxides
elements diagonally from Be to Po and some d-block elements form amphoteric molecules

so for example, SO2 is acidic because S is a nonmetal.
by Ellen Amico 2L
Sat Dec 07, 2019 10:03 am
Forum: Conjugate Acids & Bases
Topic: studying
Replies: 5
Views: 41

Re: studying

My TA told me our main focus should be strong acids and bases, but doing the homework problems and reading the textbook sections is what I'm doing to study.
by Ellen Amico 2L
Sat Dec 07, 2019 9:59 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 2oh- and oh-
Replies: 1
Views: 14

Re: 2oh- and oh-

Yeah it depends on the compound you're working with, so you have to think about how lone pairs or protons are being donated. For an oxide like CaO, you end up with 2 OH- because the oxygen takes a hydrogen from water so you form 2 OH-.
by Ellen Amico 2L
Sat Nov 16, 2019 1:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: All VSEPR structures or just ones from class?
Replies: 11
Views: 63

Re: All VSEPR structures or just ones from class?

I would remember all of them just to be safe. My TA sent a chart he made with the shapes and there's more variations on there then we went over in class.
by Ellen Amico 2L
Sat Nov 16, 2019 1:49 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Dipole Moments
Replies: 1
Views: 14

Re: Dipole Moments

You need to draw the arrow with the plus on one end, which the arrow pointing towards the more electronegative atom and the plus side towards the less electronegative atom. You can also draw the partial negatives and positives using a lowercase sigma. Do this for every bond on your structure and the...
by Ellen Amico 2L
Sat Nov 16, 2019 1:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Acids and Bases
Replies: 4
Views: 25

Re: Acids and Bases

I don't think this is something we need to know for Test 2, it's just going to cover anything after the midterm which includes Topic 3F (intermolecular forces) and VSEPR.
by Ellen Amico 2L
Sat Nov 16, 2019 1:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 9
Views: 48

Re: Bond Angles

Maya Pakulski 3D wrote:So we basically just have to memorize which bond angles go with which shapes?

Yes that's honestly the easiest way, but conceptually you should know that the reason the bond angles occur is due to repulsion between lone pairs and bonding pairs.
by Ellen Amico 2L
Sat Nov 16, 2019 1:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 24

Re: Bond Angles

You should know where the bond angles are in the structures if there's multiple. For example, in trigonal bipyramidal, you should know the 120 bond angles are between the 3 atoms in the same plane, the 90 degree angles are between the trigonal plane and the atoms above and below, and there's a 180 a...
by Ellen Amico 2L
Fri Nov 08, 2019 3:36 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: Dispersion forces
Replies: 6
Views: 34

Re: Dispersion forces

The dispersion depends on the polarizability because the the more polarizable an atom is, the more it'll affect the electron density and the more the electrons will be attracted to each other. Therefore, there will be a larger fluctuation in the dipoles and the potential energy of the interaction wi...
by Ellen Amico 2L
Fri Nov 08, 2019 3:07 pm
Forum: Resonance Structures
Topic: Formal Charge Question
Replies: 15
Views: 95

Re: Formal Charge Question

They should just sum up to the overall charge! For example if your structure is an ion that has a charge of -2, the formal charges should add up to that. But the formal charges on the atom for each resonance structure will vary because the bonds vary.
by Ellen Amico 2L
Fri Nov 08, 2019 3:02 pm
Forum: Lewis Structures
Topic: Midterm grades
Replies: 26
Views: 246

Re: Midterm grades

Lavelle said in lecture today that they'll be given back next Wednesday during lecture!
by Ellen Amico 2L
Fri Nov 08, 2019 3:00 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: Iterionic and Intermolecular force difference
Replies: 1
Views: 13

Re: Iterionic and Intermolecular force difference

Interionic forces are between ions, which are charged molecules, and intermolecular forces are between molecules, which are covalently bonded. The interionic forces are ion-ion and ion-dipole, and the IMFs are van der waals forces and hydrogen bonding.
by Ellen Amico 2L
Mon Nov 04, 2019 9:09 pm
Forum: Resonance Structures
Topic: 2B.15
Replies: 1
Views: 20

2B.15

The question is: Draw the Lewis structures that contribute to the resonance hybrid of nitryl chloride, ClNO2 (N is the central atom). I'm confused as to why there even needs to be resonance structures if both oxygens can have double bonds since nitrogen has enough electrons for it... is there a reas...
by Ellen Amico 2L
Thu Oct 31, 2019 7:20 pm
Forum: Student Social/Study Group
Topic: Midterm
Replies: 7
Views: 57

Re: Midterm

There's going to be 8 questions (with parts i'm assuming) and it covers up to Outline 3 topic 2D. I think the best way to get an idea of knowing what the questions will be like is looking at your discussion section questions and also going to Lavelle's review session of past exam questions.
by Ellen Amico 2L
Thu Oct 31, 2019 7:14 pm
Forum: Lewis Structures
Topic: Sulfur Dioxide
Replies: 2
Views: 23

Re: Sulfur Dioxide

I would always choose the structure that has the lowest formal charge, since that's what we were taught in lecture/discussion. Also, we wouldn't know what the experimental evidence is for a structure on the test so just go by the FC!
by Ellen Amico 2L
Thu Oct 31, 2019 7:10 pm
Forum: DeBroglie Equation
Topic: Question about Converting Units
Replies: 3
Views: 42

Re: Question about Converting Units

1 eV = 1.60e-19 J, so convert from keV to eV to joules (dimensional analysis is easiest).
by Ellen Amico 2L
Thu Oct 31, 2019 7:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 16
Views: 100

Re: Midterm

I'm planning on doing all the textbook questions in the syllabus for the review, quantum, and chemical bonds. This should cover everything!
by Ellen Amico 2L
Thu Oct 31, 2019 7:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 16
Views: 100

Re: Midterm

I'm planning on doing all the textbook questions in the syllabus for the review, quantum, and chemical bonds. This should cover everything!
by Ellen Amico 2L
Thu Oct 31, 2019 1:20 pm
Forum: Molarity, Solutions, Dilutions
Topic: Help with Textbook problem G.7
Replies: 1
Views: 40

Help with Textbook problem G.7

Not sure why I'm having trouble with this but I need some help on 7 from the textbook:
You need to prepare 510. g of an aqueous solution containing 5.45% KNO3 by mass. Describe how you would prepare the solution and what mass of each component you would use.
by Ellen Amico 2L
Fri Oct 25, 2019 9:49 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: second quantum number
Replies: 2
Views: 17

Re: second quantum number

Yes the number matters here! The l = 0 always refers to the s-orbital, no matter what shell it's in. So l is always the same for each type of orbital.
by Ellen Amico 2L
Fri Oct 25, 2019 9:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D 15
Replies: 2
Views: 16

Re: 1D 15

The principal quantum number refers to the shell and the orbital angular momentum number refers to which orbital the electron is in.
So for this problem it would be:
a) 6p - n = 6, l = 1
b) 3d - n = 3, l = 2
c) 2p - n = 2, l = 1
d) 5f - n = 5, l = 3
by Ellen Amico 2L
Fri Oct 25, 2019 9:44 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Expanded Valence Shells
Replies: 5
Views: 34

Re: Expanded Valence Shells

They normally don't have electrons in the d-orbital, but because they have a n=3, the d-orbital exists and is available to them to fill up with more than 8 electrons, which allows them to have an expanded octet.
by Ellen Amico 2L
Fri Oct 25, 2019 9:42 pm
Forum: Ionic & Covalent Bonds
Topic: Meaning of Brackets
Replies: 7
Views: 56

Re: Meaning of Brackets

Instead of writing out the entire electron configuration starting at 1s for an element, using the brackets of the closest previous noble gas is a shortcut and the configuration for an element will continue from there.
by Ellen Amico 2L
Fri Oct 25, 2019 9:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Topics
Replies: 5
Views: 55

Midterm Topics

Does anyone know what topics the midterm will cover? Will the high school review content from test 1 be on it too?
by Ellen Amico 2L
Sat Oct 19, 2019 9:23 pm
Forum: Properties of Light
Topic: 1A. 15
Replies: 3
Views: 33

Re: 1A. 15

I started off by finding the frequency using the wavelength and then I used the equation: frequency = -R[1/(n1)^2- 1/(n2)^2] and solved for n1, which should get you a number close to 3. I figured out n2 because the question mentioned UV radiation, which equates to the Lyman series and n2 is always 1...
by Ellen Amico 2L
Sat Oct 19, 2019 9:17 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Spin
Replies: 4
Views: 46

Re: Magnetic Spin

I don't think it's something we really have to know for the test, since each electron has one of those spin numbers. Not totally sure on why it's +/- 1/2, but I think it's because of a theorem, which we definitely don't need to know. I would just remember that it exists and is a way of specifying a ...
by Ellen Amico 2L
Sat Oct 19, 2019 9:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Values of l
Replies: 2
Views: 42

Re: Values of l

It's not that l has multiple possible values, but ml does. l represents the different subshells in an energy level (e.g. l = 2 represents the d subshell). This mean the values of ml for the d subshell can be -2, -1, 0, 1, 2. These values represent the 5 different orbitals of the d subshell.
by Ellen Amico 2L
Sat Oct 19, 2019 9:12 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 1E.7
Replies: 3
Views: 39

Re: Homework 1E.7

Yes! This matters because it violates Hund's rule, which states not only that each orbital is occupied by a single electron first, but also that all the unpaired electrons need to have parallel spins (the same spin direction).
by Ellen Amico 2L
Sat Oct 19, 2019 9:09 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell, Subshell, Orbital Terminology
Replies: 8
Views: 89

Re: Shell, Subshell, Orbital Terminology

I was super confused about this in class at first too but this is really helpful! Thanks so much for the tip!
by Ellen Amico 2L
Fri Oct 11, 2019 10:40 pm
Forum: Einstein Equation
Topic: Variables in equations
Replies: 4
Views: 40

Re: Variables in equations

The "v" for frequency isn't really a v but a greek letter, so I think of it more like a 'wavy' v and try to make it clear in my work. It's also helpful to know which equations use frequency and which use velocity off the top of your head.
by Ellen Amico 2L
Fri Oct 11, 2019 10:36 pm
Forum: Properties of Electrons
Topic: Clarification on particle vs wave properties
Replies: 3
Views: 27

Clarification on particle vs wave properties

Can someone clarify or give examples of what the particle properties of an electron are and what its wavelike properties are? I feel like there are certain experiments that show each but I'm confused on what these properties are.
by Ellen Amico 2L
Fri Oct 11, 2019 10:33 pm
Forum: Properties of Electrons
Topic: Wave Properties of Electrons
Replies: 4
Views: 32

Re: Wave Properties of Electrons

Destructive interference refers to when two waves collide "out-of-phase" in that the peak of one wave interacts with the trough of another, resulting in a smaller, weaker wave. Basically you can think of two waves that don't line up.
by Ellen Amico 2L
Fri Oct 11, 2019 10:30 pm
Forum: Properties of Electrons
Topic: Energy levels
Replies: 3
Views: 27

Re: Energy levels

I find that it's not really necessary since the question usually just involves the numbers. Just make sure to keep track of which energy level is the final one and which one is the initial, so a diagram might help you in that aspect.
by Ellen Amico 2L
Tue Oct 08, 2019 3:38 pm
Forum: Molarity, Solutions, Dilutions
Topic: Help with Textbook problem G.21
Replies: 2
Views: 50

Help with Textbook problem G.21

The question is: "A solution is prepared by dissolving 0.500 g of KCl, 0.500 g of K2S, and 0.500 g of K3PO4 in 500. mL of water. What is the concentration in the final solution of (a) potassium ions; (b) sulfide ions?" I calculated the molarity of the solution, but how do I find the concen...
by Ellen Amico 2L
Wed Oct 02, 2019 11:19 am
Forum: SI Units, Unit Conversions
Topic: Question about Showing Work
Replies: 22
Views: 204

Re: Question about Showing Work

I asked my TA specifically about balancing equations and he said you don't have to show it step by step if you just can see it and know how to balance it. Some questions have parts that make you go step by step, but I think you should just show as much work as you personally need. He did emphasize t...
by Ellen Amico 2L
Wed Oct 02, 2019 11:17 am
Forum: Administrative Questions and Class Announcements
Topic: First Test in Discussion
Replies: 13
Views: 183

Re: First Test in Discussion

The first test has to do with the modules that review high school chem.
So the topics are:
Empirical and Molecular Formulas

Balancing Chemical Equations

Limiting Reactant Calculations

Molarity and Dilution of a Solution
by Ellen Amico 2L
Wed Oct 02, 2019 11:15 am
Forum: Empirical & Molecular Formulas
Topic: Homework problem E1
Replies: 9
Views: 84

Re: Homework problem E1

Basically it's asking the for the length of a chain of 1 mol of atoms strung together. Since there's 6.02 x 10^23 atoms in a mol (avogadro's number), you would multiply the radius of one Ag atom by the number of atoms in 1 mol, which gives you the total length.
by Ellen Amico 2L
Wed Oct 02, 2019 11:12 am
Forum: Administrative Questions and Class Announcements
Topic: Tips for Tests [ENDORSED]
Replies: 4
Views: 69

Tips for Tests [ENDORSED]

Hi, just wondering if anyone has tips for studying for Lavelle's tests? I know there are plenty of practice problems in the textbook, but is there anything else/other resources people recommend doing? Thanks!
by Ellen Amico 2L
Mon Sep 30, 2019 3:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice on Homework
Replies: 13
Views: 147

Advice on Homework

Hi everyone, I was wondering if we have to do ALL the textbook questions listed in the syllabus or if we just pick 5 and do those... I just did 5 for the first assignment, but is it helpful to do more? Thanks!

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