Search found 128 matches

by Cecilia Cisneros 1F
Sat Jan 23, 2021 7:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids in Ice Tables
Replies: 11
Views: 23

Solids in Ice Tables

If we are given the concentration of a solid would we include this in our equilibrium table? I know it does not affect the equilibrium constant. Does that mean we do not include it in the table? Thanks!
by Cecilia Cisneros 1F
Thu Jan 21, 2021 8:04 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Approx K<10^-4 for Cubic
Replies: 3
Views: 14

Approx K<10^-4 for Cubic

When we approximate K^-4 for cubic reactions we do not have to check that our solution is valid with the 5% rule right? That only pertains to acid/base equilibria?
by Cecilia Cisneros 1F
Wed Jan 20, 2021 10:46 am
Forum: General Science Questions
Topic: Polyprotic Acids
Replies: 6
Views: 24

Polyprotic Acids

In the textbook their are problems where we are solving for the pH of a polyprotic acid and it is advised to ignore the 2nd deprotanation of weak polyprotic acids because Ka2 is significantly less than Ka1. The only instance where we looked at the second deprotonation was for H2SO4 because it is a s...
by Cecilia Cisneros 1F
Wed Jan 20, 2021 10:41 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Calculating the pH and percentage deprotonation of a weak acid
Replies: 8
Views: 27

Re: Calculating the pH and percentage deprotonation of a weak acid

To be safe I would approximate when the K is < 10^-4, as Dr. Lavelle had mentioned in lecture. Once you have solved for x, you would have to check the % ionized and make sure your percentage is less than 5% in order to confirm that your approximation is valid. However, If your percentage is greater ...
by Cecilia Cisneros 1F
Mon Jan 18, 2021 7:52 pm
Forum: Ideal Gases
Topic: reversing reactions
Replies: 83
Views: 398

Re: reversing reactions

For a reverse reaction, you should take the inverse of the original K in order to find the equilibrium constant (AKA: new K value)
by Cecilia Cisneros 1F
Mon Jan 18, 2021 7:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Moles vs Concentrations in ICE Box
Replies: 21
Views: 49

Re: Moles vs Concentrations in ICE Box

I tend to just use concentrations because it makes it much easier to be able to solve for equilibrium constants. I would say that is the safer bet (to use concentrations over moles) because there is a chance that you may forget to convert moles to concentration when finding equilibrium constants.
by Cecilia Cisneros 1F
Mon Jan 18, 2021 7:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K
Replies: 46
Views: 157

Re: Q and K

Essentially, yes. Q is measured at any point in the reaction that is not at equilibrium. However, K must be measured only at equilibrium.
by Cecilia Cisneros 1F
Sun Jan 17, 2021 7:52 am
Forum: General Science Questions
Topic: Matthew UA WS 2 #5
Replies: 2
Views: 37

Matthew UA WS 2 #5

5. “Acetic Acid (CH3COOH) is a common weak acid that gives vinegar its sour taste. At 25 degrees C the pKa=4.76. Suppose you titrate 100.mL of a 7.416 x 10 -3 M solution of acetic acid with an appropriate volume of 1.4682 x 10 -2 M NaOH to the equivalence point of 25 degrees C. What is the pH of the...
by Cecilia Cisneros 1F
Fri Jan 15, 2021 9:37 am
Forum: General Science Questions
Topic: Percent ionization
Replies: 2
Views: 32

Percent ionization

Does anyone know how to solve for percent ionization of an acid? I was using the formula:

% ionization = [H3O+]eq/[HA]0 x 100%

but my answer was not matching the correct answer. Thanks for your help!
by Cecilia Cisneros 1F
Thu Jan 14, 2021 10:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 6D.15 B)
Replies: 3
Views: 22

Re: Textbook 6D.15 B)

Vivian Hoang 1H wrote:

This will give you value of X, which you can then plug in to find pH.


Where did you get the 1.4x10-5?
by Cecilia Cisneros 1F
Thu Jan 14, 2021 9:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 6D.15 B)
Replies: 3
Views: 22

Textbook 6D.15 B)

This question asks to find the pH of 0.055M AlCl3. However, I am not sure where to find the Ka value in order to solve for x using the ice table. I did not see a Ka value for this in the table that I used for part 1. Does anyone know where to find it?
by Cecilia Cisneros 1F
Tue Jan 12, 2021 8:38 pm
Forum: General Science Questions
Topic: Textbook Problem 6A.19 c)
Replies: 1
Views: 32

Textbook Problem 6A.19 c)

Is the answer key or the textbook incorrect because the question acts to solve for [OH-] given [H3O+], but for part c) there it says that the molar concentration is 3.1mol*L-1 and the solutions manual says that the concentration is 3.1x10^-3 how do we know which one we are supposed to use for this q...
by Cecilia Cisneros 1F
Mon Jan 11, 2021 2:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant for water
Replies: 4
Views: 25

Re: Equilibrium constant for water

Given the fact that Kw does not change and is always equal to (10^14) and that [H3O+]=[OH-] there is only one value that could equal to Kw which is (10^-7). Also, we know that pH of water is neutral = 7 so when you solve for [H3O+] we find that it is equal to (10^-7).
by Cecilia Cisneros 1F
Mon Jan 11, 2021 2:10 pm
Forum: General Science Questions
Topic: Lecture Question [ENDORSED]
Replies: 5
Views: 38

Re: Lecture Question [ENDORSED]

You would find the -2x, -x, and +2x from the balanced chemical equation you are using for that specific problem. The easiest way to know by what factor the compounds "change" is to look at the compound that has an initial concentration and subtract from there AKA (0.482 mol of N2, you know...
by Cecilia Cisneros 1F
Mon Jan 11, 2021 2:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic Equations
Replies: 6
Views: 30

Re: Cubic Equations

So just to make sure, we only omit x when the Kc is smaller than 1.0x10^-3 right? (of course only omit the x's being subtracted and I would assume the ones being added also, but not the ones being multiplied). Also, does Kc need to be significantly less than 1.0x10^-3 or just less than 1.0x10^-3? T...
by Cecilia Cisneros 1F
Wed Jan 06, 2021 9:29 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.39 Textbook Problem
Replies: 3
Views: 71

Re: 5.39 Textbook Problem

So for part A, you begin by finding the Kc value of the equation we are looking at. From the equilibrium constant table, we see that Kc at 298 K for N2O4(g)----->2NO2(g) is equal to 6.1x10^23. We are looking at 2NO2(g)---->N2O4(g), so we want the reverse reaction, so the Kc of our reaction is 1/K o...
by Cecilia Cisneros 1F
Wed Jan 06, 2021 9:00 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Table 5G.2
Replies: 4
Views: 10

Textbook Table 5G.2

When we refer to the textbook table for the homework problems how do we know which equilibrium constant to use? I used a Kc value for a question asking to find the equilibrium concentrations, but the homework used the K value. I assumed that K by itself should only be used for finding partial pressu...
by Cecilia Cisneros 1F
Tue Jan 05, 2021 5:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling HW #9
Replies: 7
Views: 54

Re: Sapling HW #9

Q Scarborough 1b wrote:Hi there! I just realized that my sapling has a different value for the initial values of N2 and O2. So while mine would be k=36, it seems yours is K=4. Sorry for the confusion!

No worries! Thanks for your help too!
by Cecilia Cisneros 1F
Tue Jan 05, 2021 2:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling HW #9
Replies: 7
Views: 54

Re: Sapling HW #9

Yes, you are correct that K=4! To find the value at equilibrium, you need to write the K equation in terms of x. Draw an ICE table, and in the "change" row, you would subtract 2x in the NO column and add x in the N2 and O2 columns (because you are adding more product, the reaction shifts ...
by Cecilia Cisneros 1F
Tue Jan 05, 2021 1:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Boxes
Replies: 13
Views: 98

Re: ICE Boxes

Hi! Generally, changes in reactants are negative because we're using up the reactant to make a product. Therefore, changes in products are positive because we are making product by using up the reactant. I'm not really sure of any circumstances in which this rule would change, but please let me kno...
by Cecilia Cisneros 1F
Tue Jan 05, 2021 1:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Boxes
Replies: 13
Views: 98

ICE Boxes

How do we know whether to be labeling the change as a positive or negative in the ice boxes? Does it depend on the initial concentration we are given/not given?
by Cecilia Cisneros 1F
Tue Jan 05, 2021 1:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling HW #9
Replies: 7
Views: 54

Re: Sapling HW #9

Hi there, For this problem you would set the initial value of NO as .900M. We can determine the value of K from the given concentrations, which turns out to be K=36. From there, you can use an equilibrium table to find the final NO, and use K=36, since that value does not change. Hope this helps. I...
by Cecilia Cisneros 1F
Tue Jan 05, 2021 10:23 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling HW #9
Replies: 7
Views: 54

Sapling HW #9

Can anyone help me solve this problem I am having trouble figuring out where to begin. Would the initial value of NO be .900M and then how would we find the value at equilibrium is we are not given a change? Anything would be really helpful. Thanks!
by Cecilia Cisneros 1F
Tue Jan 05, 2021 8:21 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium is shifted to the right/left
Replies: 9
Views: 37

Re: Equilibrium is shifted to the right/left

I believe this refers to if the equilibrium is favoring products(right) vs. reactants (left). In terms of K that would depend on the ratio since K=[P]/[R] when K is large then equilibrium favors products and if K is small then equilibrium favors reactants.
by Cecilia Cisneros 1F
Tue Jan 05, 2021 8:14 am
Forum: Student Social/Study Group
Topic: Advice for someone who didn't take 14A with professor Lavelle
Replies: 61
Views: 259

Re: Advice for someone who didn't take 14A with professor Lavelle

I would pick a few UA sessions to attend weekly because this helps you to review the information for the week and helps you to understand what problems you may or may not understand. Also, I recommend doing all the practice problems from the outline because they are helpful to make sure you understa...
by Cecilia Cisneros 1F
Tue Jan 05, 2021 8:07 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant in terms of stability
Replies: 4
Views: 32

Equilibrium Constant in terms of stability

Could someone help explain the equilibrium constant in terms of stability? I got a bit confused when Dr. Lavelle mentioned this in lecture.
by Cecilia Cisneros 1F
Sat Dec 12, 2020 12:13 am
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 8
Views: 43

Re: Atomic Radius

The ion with the larger atomic radius would be the one with the less positive charge. In this case, it would be Fe 2+. The reason being is that the one with the lesser positive charge has more electron repulsion between the electrons which result in the radius to be slightly expanded. For the more ...
by Cecilia Cisneros 1F
Fri Dec 11, 2020 11:16 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 8
Views: 43

Atomic Radius

How do we know between ions of the same element, which ion may have a larger atomic radius?

Fe2+ vs. Fe3+

Also, do isoelectronic elements have the same size radius? I know they have the same number of electrons, but I am not sure if they have the same atomic radius.
by Cecilia Cisneros 1F
Thu Dec 10, 2020 8:51 pm
Forum: Amphoteric Compounds
Topic: Amphoteric
Replies: 8
Views: 90

Amphoteric

Would we be asked to see how an amphoteric compound will act as an acid or base in water? (pH <,>,= 7) OR do those types of questions just refer to analyzing salts?
by Cecilia Cisneros 1F
Wed Dec 09, 2020 10:25 pm
Forum: Conjugate Acids & Bases
Topic: Neutralization
Replies: 3
Views: 53

Neutralization

I'm having a lot of trouble writing out the formulas for neutralization of acids and bases to salts does anyone have any tips!! Should we be writing them in the ionic forms like the textbook or can we leave them as compounds?
by Cecilia Cisneros 1F
Wed Dec 09, 2020 9:55 pm
Forum: Bronsted Acids & Bases
Topic: Fundamentals J.7 b)
Replies: 1
Views: 33

Fundamentals J.7 b)

We are asked to write the neutralization of the salt by selecting an acid and base that would result in the formation of the given salt. How are we supposed to know that Zn(OH)2 is written in this format? We are not given the charge for Zinc so I was just confused as to how we should know this?
by Cecilia Cisneros 1F
Tue Dec 08, 2020 10:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: Angular Quantum Number
Replies: 3
Views: 25

Angular Quantum Number

Does the angular momentum quantum number "l" give only the number of angular nodes or does it give the number of nodal planes?
by Cecilia Cisneros 1F
Tue Dec 08, 2020 10:03 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Radicals
Replies: 3
Views: 34

Radicals

How do we know which atom the single electron would be placed when drawing the lewis structure of a radical?
by Cecilia Cisneros 1F
Tue Dec 08, 2020 4:40 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: IMFs
Replies: 2
Views: 32

IMFs

Are there any H-bonds present in the compound: H2SeO4? Question 3F.1 says there are, but I didn't think there were any present.
by Cecilia Cisneros 1F
Tue Dec 08, 2020 1:44 pm
Forum: Bond Lengths & Energies
Topic: Compound stability
Replies: 5
Views: 36

Compound stability

If we are asked to determine the most stable compound should we be looking at the bond lengths or IMFs?
by Cecilia Cisneros 1F
Mon Dec 07, 2020 11:27 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: edta ligand
Replies: 2
Views: 30

edta ligand

Is the hexadentate ligand "edta" charged? It is in the anionic section on the list of ligands on the class textbook, but I cannot seem to find the charge on it.
by Cecilia Cisneros 1F
Mon Dec 07, 2020 11:10 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Cl- not effecting pH
Replies: 5
Views: 45

Cl- not effecting pH

How do we know that Na+ and Cl- do not effect the pH. Dr. Lavelle mentioned that they don't, but I was unsure as to why that was the case.
by Cecilia Cisneros 1F
Fri Dec 04, 2020 8:58 am
Forum: Naming
Topic: Coordination Complex Anion
Replies: 2
Views: 32

Coordination Complex Anion

If the coordination complex is an anion I understand that we add the suffix -ate to the transition metal. Do we still need to add the oxidation number in roman numerals at the very end of the coordination compound name?
by Cecilia Cisneros 1F
Thu Dec 03, 2020 7:52 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Compound
Replies: 6
Views: 49

Coordination Compound

What would be the formula to:
triamminediaquafluorocobalt(III) bromide?

I was practicing and came across this question, but I'm not sure if I'm right. Im thinking its:
[Co(NH3)3(OH2)2F] Br2
by Cecilia Cisneros 1F
Wed Dec 02, 2020 11:27 am
Forum: Bronsted Acids & Bases
Topic: Strong Acid vs. Weak Acid
Replies: 7
Views: 68

Strong Acid vs. Weak Acid

How do we differentiate acids as being strong acids vs. weak acids? Dr. Lavelle listed some for us, but how do we determine this ourselves when given different compounds?
by Cecilia Cisneros 1F
Wed Dec 02, 2020 10:50 am
Forum: Bronsted Acids & Bases
Topic: HCl vs. HBr
Replies: 6
Views: 52

HCl vs. HBr

Is HCl or HBr the stronger acid? Dr. Lavelle said that HBr is the stronger acid, but the bond between HBr is longer than the bond between HCl. Longer bonds are weaker bonds. So now I'm not sure how HBr can be stronger than HCl.
by Cecilia Cisneros 1F
Tue Dec 01, 2020 11:03 pm
Forum: Naming
Topic: Nitrito
Replies: 2
Views: 36

Nitrito

When writing nitrito does it matter if we write it in the formula of the coordination compound as "ONO" or "NO2".
Would there be a difference as to which is more correct?
by Cecilia Cisneros 1F
Tue Dec 01, 2020 11:01 pm
Forum: Naming
Topic: use of bis,tris,etc
Replies: 3
Views: 44

Re: use of bis,tris,etc

One of the UA's mentioned that a good note to have is that: the bis,tris,etc prefixes are mainly used for polydentate ligands. So if you have multiples of a polydentate ligand then you would use those prefixes.
by Cecilia Cisneros 1F
Mon Nov 30, 2020 10:59 am
Forum: Biological Examples
Topic: Hemoglobin vs. Myoglobin
Replies: 29
Views: 225

Re: Hemoglobin vs. Myoglobin

Hemoglobin is primarily for oxygen transport in the blood and is the main mechanism used in our bodies for oxygen transport because it can hold more oxygen than myoglobin. On the other hand, myoglobin is only used when we are in need a quick bursts of oxygen for example in the tissue while we are wo...
by Cecilia Cisneros 1F
Mon Nov 30, 2020 10:56 am
Forum: Naming
Topic: Formula from Naming
Replies: 3
Views: 30

Formula from Naming

When we are asked to give the formula of a coordination compound is there a specific order that the ligands are placed in the compound? I know that they must be written alphabetically in the compound name, but does it matter in which order we write the ligands in the formula?
by Cecilia Cisneros 1F
Fri Nov 27, 2020 6:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair VSEPR
Replies: 5
Views: 57

Lone Pair VSEPR

Do lone pairs cause the bonding regions to be slightly smaller than the base geometry because they occupy a larger volume?
by Cecilia Cisneros 1F
Wed Nov 25, 2020 10:29 pm
Forum: Hybridization
Topic: UA Workshop Number 6a
Replies: 4
Views: 67

UA Workshop Number 6a

Hi! I attended Matthew Tran's workshop earlier, but I didn't get to stay at until the end. I was reviewing my answers with the answers from the workshop that someone kindly shared with me, but I was having trouble understanding the answer to 6a. "6. For each of the following molecules, identify...
by Cecilia Cisneros 1F
Wed Nov 25, 2020 11:14 am
Forum: Determining Molecular Shape (VSEPR)
Topic: sapling HW question three
Replies: 5
Views: 47

Re: sapling HW question three

Well the molecule has five areas of electron density. The VSEPR formula is AX2E3, so you know that it began with a base geometry of trigonal bipyramidal. Once you remove 3 bonds for lone pairs, you are left with a linear shape and the bond angle would be 180 degrees. I usually like to work my way do...
by Cecilia Cisneros 1F
Wed Nov 25, 2020 10:10 am
Forum: Hybridization
Topic: S-character
Replies: 3
Views: 31

S-character

Can anyone explain what s-character is?
by Cecilia Cisneros 1F
Tue Nov 24, 2020 10:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.7
Replies: 3
Views: 21

Re: 2E.7

Lisa Wang 2J wrote:Please correct me if I am wrong, but I believe the size of the atom do not factor into the bond angle.

You could be totally right. I was just wondering if that had any effect on bond angle, but I could be completely overthinking it.
by Cecilia Cisneros 1F
Tue Nov 24, 2020 10:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: equatorial vs. axial atom positions
Replies: 4
Views: 13

Re: equatorial vs. axial atom positions

In the trigonal bipyramidal structure you should identify the 3 atoms that form the trigonal planar structure and these atoms are the in equatorial position and then the remaining two atoms (positioned above and below the trigonal planar) would be the two atoms in the axial positions. I think of it ...
by Cecilia Cisneros 1F
Tue Nov 24, 2020 10:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.7
Replies: 3
Views: 21

2E.7

In part c, the question asks: (c) What values are expected for the OSCl and ClSCl bond angles?

If the shape of the molecule is trigonal pyramidal are we able to conclude that all bond angles are less than 109.5 regardless of the size of the atom?
by Cecilia Cisneros 1F
Tue Nov 24, 2020 4:00 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and pi bonds relation to covalent bonds
Replies: 6
Views: 48

Re: Sigma and pi bonds relation to covalent bonds

When two atoms are bound by one covalent bond this is known as a sigma bond. Whereas when two atoms are bound by two covalent bonds then there is one sigma bond and one pi bond.
by Cecilia Cisneros 1F
Thu Nov 19, 2020 7:21 pm
Forum: Resonance Structures
Topic: Lowest Energy Lewis Structure
Replies: 8
Views: 83

Lowest Energy Lewis Structure

Would the lowest energy structure be the one where the negative FC is on the most electronegative atom? For example the structure of NO2. It could be drawn two ways with a +1 charge on central N atom and a -1 on the O OR a +1 charge on the central N atom and a -1 charge on the other N atom. Which wo...
by Cecilia Cisneros 1F
Wed Nov 18, 2020 9:12 pm
Forum: Octet Exceptions
Topic: Textbook Problem 2C.1
Replies: 2
Views: 17

Re: Textbook Problem 2C.1

Also, I think you could tell which molecule is a radical based on the number of valence electrons between the atoms. If it is an odd number you know that there will be one electron that is unpaired, so it is a radical. At least that has worked for me!
by Cecilia Cisneros 1F
Wed Nov 18, 2020 9:09 pm
Forum: Dipole Moments
Topic: Dipole Dipole Interactions
Replies: 7
Views: 53

Re: Dipole Dipole Interactions

I think C-Cl would experience dipole-dipole interactions. I believe that dipole-dipole interactions occur when there is a difference between electronegativities in a molecule. However, they do not occur in nonpolar molecules. At least that is the way I think of it. Yeah that's what I'm thinking too...
by Cecilia Cisneros 1F
Wed Nov 18, 2020 7:13 pm
Forum: Dipole Moments
Topic: Dipole Dipole Interactions
Replies: 7
Views: 53

Dipole Dipole Interactions

Would a bond between C-Cl be enough to experience dipole-dipole interactions? How do we determine whether there is a dipole moment present if we are just given the molecular formula and the molecule does not include N,O,F (the most electronegative atoms on the PT).
by Cecilia Cisneros 1F
Tue Nov 17, 2020 9:05 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 4
Views: 37

Resonance

Can someone explain how the other two lewis structures are apart of the resonance structures? I thought resonance would have to be only with the lowest energy structure. In this case isn't the last one the only one that would be the lowest energy structure with all formal charges = 0. Therefore this...
by Cecilia Cisneros 1F
Tue Nov 17, 2020 4:34 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: ElectronConfigurations
Replies: 3
Views: 17

ElectronConfigurations

When we are writing the electron configuration of (For Example: Br-) would it be acceptable to write it as either [Kr] or [Ar]3d^10 4s^2 4p^6? Is one preferred over the other?
by Cecilia Cisneros 1F
Mon Nov 16, 2020 11:14 pm
Forum: Quantum Numbers and The H-Atom
Topic: London Dispersion Forces
Replies: 7
Views: 65

Re: London Dispersion Forces

London Dispersion Forces are synonymous with Induced Dipole-Induced Dipole, Van Der Waals, and Dispersion forces. These type of intermolecular forces tend to appear in all molecules, and when non polar molecules interact with each other they only experience LDFs.
by Cecilia Cisneros 1F
Mon Nov 16, 2020 11:12 pm
Forum: Bond Lengths & Energies
Topic: Higher Melting Point
Replies: 5
Views: 49

Re: Higher Melting Point

I would say yes because NaCl would contain ion-ion forces and HCl would only contain induced dipole-induced dipole. The relationship between melting point and IMFs is that stronger IMFs have higher melting points.
by Cecilia Cisneros 1F
Mon Nov 16, 2020 11:10 pm
Forum: Student Social/Study Group
Topic: grade worries
Replies: 110
Views: 1173

Re: grade worries

Yes I agree with you! I think it may also be because the anxiety of the midterm tends to creep up on you as the midterm is approaching and you can't help but just worry about your grade! As long as you are studying the topics effectively I'm sure it will reflect in your exams! You got this :)
by Cecilia Cisneros 1F
Mon Nov 16, 2020 11:07 pm
Forum: Ionic & Covalent Bonds
Topic: Lecture 16 More explanation
Replies: 1
Views: 13

Re: Lecture 16 More explanation

For this question I would think you can look at it both ways. The general guideline I follow for polarizability is that the bigger the anion the more polarizable. Since (I) is bigger then (F), (I) would be more polarizable than (F). In addition, bigger anions have more electrons than smaller anions ...
by Cecilia Cisneros 1F
Mon Nov 16, 2020 1:26 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electrostatic Coloumb Potential
Replies: 1
Views: 37

Electrostatic Coloumb Potential

Do we only need to know that the charge and distance between charges is what effects the energy of an electron in a multi-electron system? Or would it just be more generally looking at effective nuclear charge for particular atoms?
by Cecilia Cisneros 1F
Mon Nov 16, 2020 10:55 am
Forum: Dipole Moments
Topic: Dipole Moment
Replies: 7
Views: 83

Dipole Moment

If asked if a molecule has a dipole moment and the molecule has no net dipole moment since the dipoles cancel (for ex: CO2) would it still be considered to have a dipole moment?
by Cecilia Cisneros 1F
Sat Nov 14, 2020 7:01 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Palladium
Replies: 1
Views: 8

Palladium

Is there a rule that we should know to know that the ground-state electron confuguration of palladium is [Kr]4d^10?
Why is the 5s empty? Does this occur for every element with 8 electrons in the d-orbital?
by Cecilia Cisneros 1F
Sat Nov 14, 2020 6:46 pm
Forum: Dipole Moments
Topic: H-Bond acceptor
Replies: 9
Views: 70

H-Bond acceptor

Does an H-bond acceptor (O,N, or F) need to be attached to a hydrogen atom to participate in h-bonds?
by Cecilia Cisneros 1F
Fri Nov 13, 2020 1:14 pm
Forum: Dipole Moments
Topic: Vapor Pressure and Boiling Points
Replies: 1
Views: 10

Vapor Pressure and Boiling Points

I understand the relationship between IMFs and Boiling points. Where molecules that have stronger IMFs would be more tightly bound so you would need a higher boiling point to unbind electrons. However, what is the relationship between IMF strength and vapor pressure?
by Cecilia Cisneros 1F
Thu Nov 12, 2020 4:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B [ENDORSED]
Replies: 3
Views: 526

Chem 14B [ENDORSED]

Hello,
I'm not sure if this true, but I had heard that everyone on the waitlist for Chem 14B would get into the class? With enrollment coming up I want to plan enrolling in my classes accordingly. Can anyone confirm this?
by Cecilia Cisneros 1F
Wed Nov 11, 2020 1:36 pm
Forum: Dipole Moments
Topic: Dipole Dipole vs Induce Dipole Induced Dipole
Replies: 2
Views: 15

Re: Dipole Dipole vs Induce Dipole Induced Dipole

I believe another hint to let you know would be if an atom is bound to one of the high electronegative atoms (O,N,F). In the case where an atom is bound to one of those, then the electrons would be pulled closer to the more electronegative atom and cause a dipole moment on the compound. Dipole-Dipol...
by Cecilia Cisneros 1F
Wed Nov 11, 2020 1:31 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Textbook 2D.3
Replies: 2
Views: 17

Re: Textbook 2D.3

Hey Cecilia, I would say for this problem you're going to need to use electronegativity. You're right in saying that you can use electronegativity to compare covalent bonds and polarizability to compare ionic bonds. It's just that in this case you're actually looking at a set of compounds with mixe...
by Cecilia Cisneros 1F
Tue Nov 10, 2020 11:05 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: increasing polarizability
Replies: 5
Views: 48

Re: increasing polarizability

Bigger anions will have a greater polarizability. Therefore, if you are ranking N3-, O2-, F-, and Cl- you could look at the atomic radius to deduce which anion is the largest and that would be the anion with the greatest polarizability. The order of increasing polarizability would be from smallest t...
by Cecilia Cisneros 1F
Tue Nov 10, 2020 10:25 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Textbook 2D.3
Replies: 2
Views: 17

Textbook 2D.3

I approached this problem looking at the polarizability of the compounds since these are ionic compounds. Which led me to believe that BBr3 would have the most primarily ionic bonds, since it is the smallest, most positively charged ion out of the three cations bound to Br (which means it has the gr...
by Cecilia Cisneros 1F
Tue Nov 10, 2020 8:16 pm
Forum: Electronegativity
Topic: Electronegativity Difference for Covalent and Ionic Bonds
Replies: 6
Views: 37

Re: Electronegativity Difference for Covalent and Ionic Bonds

If the value falls within 1.5-2 Dr. Lavelle mentioned in lecture that we would have to analyze the bond to see if it has a greater ionic or covalent character. However, for our purposes I believe they would give us a value that would be obvious in determining whether it is ionic or covalent. I.e. >2...
by Cecilia Cisneros 1F
Tue Nov 10, 2020 8:13 pm
Forum: Dipole Moments
Topic: London Dispersion forces
Replies: 7
Views: 34

Re: London Dispersion forces

Hello, to my knowledge I don't believe there are any exceptions to London Dispersion Forces. All molecules interacting with each other should experience London dispersion forces!
by Cecilia Cisneros 1F
Tue Nov 10, 2020 5:58 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s before 3d?
Replies: 6
Views: 77

4s before 3d?

I wanted to clarify the 4s is lower in energy that is why the orbital is filled with electrons first and that is why it comes before 3d when writing electron configurations. However, why is it that when an atom loses electrons is loses them from the 4s before the 3d? Could someone clarify?
by Cecilia Cisneros 1F
Fri Nov 06, 2020 11:23 am
Forum: Lewis Structures
Topic: 2B.3 part d)
Replies: 2
Views: 30

Re: 2B.3 part d)

Oh yes I think that was where I confused the expanded octet rule! Thank you!
by Cecilia Cisneros 1F
Fri Nov 06, 2020 9:49 am
Forum: Lewis Structures
Topic: 2B.3 part d)
Replies: 2
Views: 30

2B.3 part d)

In this question we are asked to draw the Lewis structure for BrF3. I drew my lewis structure with Br as the central atom and two of the F atoms had a single bond with Br and 6 lone pair electrons. For the third F, I drew a triple bond with Br and then 4 lone pair electrons. In addition, my Br had 2...
by Cecilia Cisneros 1F
Thu Nov 05, 2020 10:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground-State Electron Configuration
Replies: 3
Views: 22

Ground-State Electron Configuration

When asked for ground-state electron configurations would we write out the FULL electron configuration or the noble gas electron configuration? Would both be acceptable for example on an exam?
by Cecilia Cisneros 1F
Wed Nov 04, 2020 9:00 pm
Forum: Lewis Structures
Topic: Electrons in Lewis Structures
Replies: 8
Views: 41

Re: Electrons in Lewis Structures

Looking at the row in the periodic table always helps me. When you count the rows [1,2,13,14,15,16,17,18] when you omit the d block. You can see that the number of electrons correspond to the row because there are 8 rows. Hope that makes sense! Quick question, can you explain why you omit the d-blo...
by Cecilia Cisneros 1F
Wed Nov 04, 2020 8:52 pm
Forum: Trends in The Periodic Table
Topic: Effective nuclear charge
Replies: 5
Views: 46

Effective nuclear charge

Can someone help explain effective nuclear charge and what it means. Also when asked about two different atoms how do we know which has a stronger/weaker effective nuclear charge. For ex) effective nuclear charge between Si and Al.
by Cecilia Cisneros 1F
Wed Nov 04, 2020 10:40 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Equation
Replies: 16
Views: 72

Re: Formal Charge Equation

The L represents the number of lone pairs and it can be found by the number of electrons on an element that are not shared between another element.
by Cecilia Cisneros 1F
Wed Nov 04, 2020 10:17 am
Forum: Lewis Structures
Topic: Electrons in Lewis Structures
Replies: 8
Views: 41

Re: Electrons in Lewis Structures

Looking at the row in the periodic table always helps me. When you count the rows [1,2,13,14,15,16,17,18] when you omit the d block. You can see that the number of electrons correspond to the row because there are 8 rows. Hope that makes sense!
by Cecilia Cisneros 1F
Wed Nov 04, 2020 10:14 am
Forum: Lewis Structures
Topic: ionization energy vs. electronegativity
Replies: 5
Views: 23

ionization energy vs. electronegativity

On sapling it directed to place the least electronegative atom as the center atom in a lewis structure. However, Dr. Lavelle mentioned in lecture that we should place the element with the lowest ionization in the center. Should we be following only one guideline and if so which one?
by Cecilia Cisneros 1F
Fri Oct 30, 2020 10:25 am
Forum: Ionic & Covalent Bonds
Topic: Octet Rule Lecture 12
Replies: 7
Views: 44

Octet Rule Lecture 12

Wouldn't Boron also be included in the exception to the octet rule since it loses 3 electrons to become like He? Therefore, it would never have an octet?
by Cecilia Cisneros 1F
Wed Oct 28, 2020 7:41 pm
Forum: Molarity, Solutions, Dilutions
Topic: Dilution module
Replies: 6
Views: 65

Dilution module

Are the units to these answers supposed to be in L? Since the volume they give us is in liters, and when you use the equation
Minitial*Vinitial = Mfinal*Vfinal
the units you get for the final volume are liters, right?
by Cecilia Cisneros 1F
Wed Oct 28, 2020 10:56 am
Forum: Empirical & Molecular Formulas
Topic: Emp/Molecular ratio
Replies: 2
Views: 46

Emp/Molecular ratio

In a practice problem I was trying to solve for the molecular formula but the ratio of the molar mass between the molecular formula and the empirical formula was not a whole number. What should I do in this instance? This was the problem: "After analyzing a sample of lactose there was found to ...
by Cecilia Cisneros 1F
Mon Oct 26, 2020 8:03 pm
Forum: Photoelectric Effect
Topic: Finding the wavelength of an ejected atom
Replies: 4
Views: 43

Re: Finding the wavelength of an ejected atom

If you found the KE then you can use the equation:
KE = 1/2mv^2 to solve for the velocity of the electron.
Then you can use the de broglie equation:
wavelength = h/mv to solve for the wavelength of the electron.
by Cecilia Cisneros 1F
Mon Oct 26, 2020 7:59 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Change in Velocity Uncertainty
Replies: 4
Views: 67

Re: Change in Velocity Uncertainty

You multiply the given uncertainty of your velocity when its a "±". Because the uncertainty is the difference between the ± 0.1m/s Uncertainty of velocity = difference = (0.2m/s -0.0m/s) = 0.2m/s Subtracting the difference is the same as multiplying by 2. You do not multiply 2 when they ex...
by Cecilia Cisneros 1F
Mon Oct 26, 2020 7:56 pm
Forum: Limiting Reactant Calculations
Topic: What counts as theoretical yield?
Replies: 8
Views: 79

Re: What counts as theoretical yield?

The theoretical yield would be the amount of product you find when converting from your limiting reactant based on a certain chemical reaction. It is the "perfect" reaction and amount of product that would come about from reacting your two reactants and there are no side reactions present....
by Cecilia Cisneros 1F
Mon Oct 26, 2020 7:51 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: position units
Replies: 19
Views: 124

Re: position units

I convert to m to be consistent with the velocity (m/s) and momentum (kg*m/s). I think that is always the best way to go! So long as all your units match up you should be good to go.
by Cecilia Cisneros 1F
Mon Oct 26, 2020 7:36 pm
Forum: Photoelectric Effect
Topic: 1B.15
Replies: 3
Views: 51

1B.15

1B.15 The velocity of an electron that is emitted from a metallic surface by a photon is 3.6×10^3km⋅s−1. (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50×10^16Hz. How much energy is requir...
by Cecilia Cisneros 1F
Sun Oct 25, 2020 10:53 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect [ENDORSED]
Replies: 4
Views: 79

Photoelectric Effect [ENDORSED]

Can someone help me understand part C for this question? In the manual it says its based on the wave model, but if someone could explain it further I would appreciate it!
by Cecilia Cisneros 1F
Sat Oct 24, 2020 7:58 pm
Forum: Photoelectric Effect
Topic: Calculations
Replies: 18
Views: 97

Calculations

As a general rule of thumb should we be doing our calculations by using the entire number that we get on our calculator? I was solving a photoelectric effect problem and my answer was not matching with one of the workshop worksheet answers. They rounded to 2 sig figs when they plugged values other t...
by Cecilia Cisneros 1F
Fri Oct 23, 2020 10:05 pm
Forum: Properties of Electrons
Topic: Rydberg
Replies: 10
Views: 83

Rydberg

Is there a big difference if we use nf and ni instead of n1 and n2 in the Rydberg equation? Thanks in advance!
by Cecilia Cisneros 1F
Fri Oct 23, 2020 10:01 pm
Forum: Properties of Electrons
Topic: Sapling Homework Week 2 question 8
Replies: 3
Views: 50

Re: Sapling Homework Week 2 question 8

I would combine the two above answers to solve for this question. You know that the emission is from a red light meaning this is apart of the Balmer series, so the ending energy level will be n=2. Then you can plug in that value and find the frequency from the wavelength provided in the question (to...
by Cecilia Cisneros 1F
Tue Oct 20, 2020 1:31 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Sapling Q 26
Replies: 2
Views: 33

Re: Sapling Q 26

Wow thank you I just found my mistake!!
by Cecilia Cisneros 1F
Mon Oct 19, 2020 11:55 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Sapling Q 26
Replies: 2
Views: 33

Sapling Q 26

I tried solving the second part to this problem, but I couldn't seem to get the right answer. "What is the minimum uncertainty in a helium atom's velocity (Δvmin) if the position is known within 1.4 Å." I did convert the molar mass of helium to kg and then I used Heisenberg's uncertainty p...
by Cecilia Cisneros 1F
Mon Oct 19, 2020 8:37 pm
Forum: Photoelectric Effect
Topic: Sapling Q 7
Replies: 2
Views: 56

Sapling Q 7

How many photons with a wavelength of 857 nm are needed to melt 417 g of ice? The enthalpy of fusion of water can be found in this table. I solved this problem by multiplying the enthalpy of fusion with the mass of ice to get the energy needed to melt the ice. From there I solved for the energy of t...
by Cecilia Cisneros 1F
Mon Oct 19, 2020 10:31 am
Forum: Properties of Light
Topic: Midterm
Replies: 5
Views: 54

Re: Midterm

Thanks! Thats what I was thinking too.

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