## Search found 60 matches

Wed Jan 13, 2021 10:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Lecture 4 cubic problem
Replies: 6
Views: 42

### Re: Lecture 4 cubic problem

Dr Lavelle emphasized how difficult it is to solve cubics so I was under the impression that the only time cubics will be involved is when the x value is small enough to not affect the other numbers so that solving for x will be simplified. If we did ever have to solve for a cubic, I am sure he woul...
Wed Jan 13, 2021 10:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH and pKa
Replies: 6
Views: 26

### Re: pH and pKa

Both refer to acids and bases but pKa is specifically related to dissociation and how much the substance will dissociate in water while pH is simply the acidity of the substance.
Wed Jan 13, 2021 10:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Dilute Solution
Replies: 4
Views: 15

### Re: Dilute Solution

I would say the same thing. Unless specified, the solvent used to dilute can be assumed to be water.
Wed Jan 13, 2021 10:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Increase in Pressure
Replies: 15
Views: 43

### Re: Increase in Pressure

Pressure with a change in volume will always only be applicable to gases. In order to use Le Chatelier's principle that it will balance out pressure, the substances need to be gaseous.
Wed Jan 13, 2021 10:20 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Getting two positive x values when using quadratic
Replies: 43
Views: 157

### Re: Getting two positive x values when using quadratic

This happened to me when I was doing the sapling homework! Most of the time, when it comes to calculating equilibrium concentration, there is an initial value that you subtract x from. The larger value is most likely the one that will not work because once you subtract the larger number from the ini...
Thu Jan 07, 2021 10:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Audio-Visual Topics
Replies: 13
Views: 54

### Re: Audio-Visual Topics

For 14A, the audio-visual topics were only used before the class as an intro and a reminder of what we've learned. I assume it will be the same and the sapling and textbook questions will be the practice throughout the course.
Thu Jan 07, 2021 10:32 pm
Forum: Ideal Gases
Topic: reversing reactions
Replies: 80
Views: 387

### Re: reversing reactions

K becomes inverted. The way to remember this is that when an equation is reversed, what was once the products (numerator) becomes the reactants (denominator) and vice versa so the K equation would flip.
Thu Jan 07, 2021 10:29 pm
Forum: Ideal Gases
Topic: Kc for Gases
Replies: 11
Views: 75

### Re: Kc for Gases

I think it would depend on the equation. If the K equation is entirely gas you can use Kp but if some are aqueous solutions and some are gases then you have to use concentration and solve for Kc.
Thu Jan 07, 2021 10:24 pm
Forum: Administrative Questions and Class Announcements
Topic: Proctored Exam?
Replies: 13
Views: 91

### Re: Proctored Exam?

The tests were all multiple choice for 14A but he might change it up for this quarter! Though he does say that the two are similar so I have a feeling they'll be the same. And to proctor you have to have a second device so that you can zoom your TA and show your work station while Respondus is on yo...
Thu Jan 07, 2021 10:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc
Replies: 11
Views: 40

### Re: Kc

Yes, Kc is always calculated from molarity which is the concentration but Kp is always calculated by partial pressure.
Wed Dec 09, 2020 11:38 am
Forum: Conjugate Acids & Bases
Topic: Conjugates and Charge
Replies: 8
Views: 46

### Re: Conjugates and Charge

You can look at the number of protons, or H+, that are taken away or added and change the charge for that! When you take an H+ from an acid, the conjugate base has a charge that is one less from the acid. When you add an H+ to a base to form a conjugate acid, the resulting acid has a charge that is ...
Tue Dec 08, 2020 12:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity in intermolecular forces
Replies: 2
Views: 27

### Re: polarity in intermolecular forces

For induced dipole-induced dipole bonds, or dispersion, those are present in every intermolecular interaction so it can occur both with non-polar and polar molecules. However, with non polar molecules, they are the only intermolecular force present. Dipole-dipole and hydrogen bonds require polar mol...
Tue Dec 08, 2020 12:24 pm
Forum: Administrative Questions and Class Announcements
Topic: Review Midterm Mistakes
Replies: 3
Views: 32

### Review Midterm Mistakes

Is there a way for me to access my past midterms to see what mistakes I have made and fix them? I tried CCLE but I can't access the test even though it has been graded and I wanted to make sure that I don't make the same mistakes on the final.
Mon Dec 07, 2020 5:24 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: H3O+ versus H+
Replies: 16
Views: 113

### H3O+ versus H+

When calculating pH, I have seen calculations that use the concentration of H+ and calculations that use the concentration of H3O+. Is there a different calculation between the two? Or are they different because the question provided different information?
Mon Dec 07, 2020 5:21 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: From pOH- to [H+]
Replies: 3
Views: 28

### Re: From pOH- to [H+]

The simplest way to do this would be to subtract the pOH from 14 to get the pH. Then, use pH=-log[H+] to solve for [H+], which would be 10^(-pH).
Tue Dec 01, 2020 9:42 pm
Forum: Hybridization
Topic: How to find the hybridization
Replies: 14
Views: 93

### Re: How to find the hybridization

Counting the regions of electron density is the simplest way to find the hybridization. 2 regions = sp, 3 regions = sp^2, and so on.
Tue Dec 01, 2020 9:40 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: Overall Review of Intermolecular Forces
Replies: 4
Views: 38

### Re: Overall Review of Intermolecular Forces

I think the most common usage of this idea would be boiling/freezing/melting points! The stronger the intermolecular force, the higher the boiling/melting points because they require more energy to break the stronger bond.
Tue Dec 01, 2020 9:38 pm
Forum: SI Units, Unit Conversions
Topic: How to memorize prefixes
Replies: 22
Views: 207

### Re: How to memorize prefixes

For me, a table was actually the most helpful for me! I used the table for every problem I completed until I was naturally doing it without checking the table because it became a force of habit! Maybe try to memorize them in order so you don't have to match them up individually, but you know the lis...
Tue Dec 01, 2020 9:36 pm
Forum: Naming
Topic: Textbook problem 9c.3
Replies: 4
Views: 47

### Re: Textbook problem 9c.3

If the compound ends in -ate, then it is a negative compound but I believe the charge would be specified if it was positive rather than neutral. I just assume the compound is neutral and because of that assumption, you must have 3 potassiums to balance out the charge.
Tue Dec 01, 2020 9:33 pm
Forum: Naming
Topic: Lecture Example [Co(Nh3)5 Cl]Cl2H2O
Replies: 8
Views: 52

### Re: Lecture Example [Co(Nh3)5 Cl]Cl2H2O

If the atoms are outside of the bracket they are not within the coordination sphere so they are not a part of the coordination compound. Because of that, you name them as you would normally, not with the ligand endings.
Mon Nov 30, 2020 12:28 pm
Forum: Bond Lengths & Energies
Topic: London Dispersion Forces/ van der Waal forces
Replies: 8
Views: 66

### Re: London Dispersion Forces/ van der Waal forces

He introduced the force and listed all the potential names but those are the same thing! He did say he prefers the term induced dipole induced dipole, I think because it gives a good summary of what is occurring when these forces are at play.
Mon Nov 30, 2020 12:27 pm
Forum: Hybridization
Topic: Two Pi Bonds?
Replies: 4
Views: 45

### Re: Two Pi Bonds?

I also believe that one of those shared regions is considered a sigma bond, if I remember correctly. One overlap represents a sigma bond but any additional overlap are pi bonds.
Mon Nov 30, 2020 12:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equatorial/ Axial Planes
Replies: 14
Views: 73

### Re: Equatorial/ Axial Planes

The atoms bonded to the central atom should be as far away from each other as possible because of repulsion. I think that is the greatest determining factor as to what shape the molecule is and then you can see which atoms are equatorial and which are axial.
Mon Nov 30, 2020 12:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Type of Bond from Shape
Replies: 12
Views: 48

### Re: Determining Type of Bond from Shape

The type of bond is based on how many bonds exist in one region of density. Shape can only help you determine how many sigma bonds there are because one exists in each bond but you have to create the Lewis structure to determine if any bonds are double or triple because that is where pi bonds come in.
Mon Nov 30, 2020 12:21 pm
Forum: Naming
Topic: Using ido or o
Replies: 24
Views: 134

### Re: Using ido or o

He used -o in his lecture so to be safe, I'd say use -o because that's what he presented to us.
Fri Nov 20, 2020 3:49 pm
Forum: Dipole Moments
Topic: higher dipole moment sapling #10
Replies: 5
Views: 59

### Re: higher dipole moment sapling #10

Dipole moments are based on electron density and with COF2, the two F's are balanced but there are far more electrons in an F atom than an H atom so the electron density is less balanced than if there are two of the same atoms on either side.
Fri Nov 20, 2020 3:47 pm
Forum: Dipole Moments
Topic: Dipole Moments Cancelling out
Replies: 10
Views: 90

### Re: Dipole Moments Cancelling out

I always look to see if there's a way that i can fold the molecule to find symmetry. So if you were to cut the molecule in half and fold it, you would have two pieces that are identical which means the dipole moments cancel out.
Fri Nov 20, 2020 3:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: determining molecular shape
Replies: 10
Views: 78

### Re: determining molecular shape

CO2 is nonpolar because it is symmetrical and has no lone pairs. The lone pair on the S atom in SO2 distorts it and repels the atoms down into a bent molecular shape.
Fri Nov 20, 2020 3:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling HW Question 6
Replies: 2
Views: 32

### Re: Sapling HW Question 6

I also got confused on this question because I assumed that you needed an even number of lone pairs in order to distort it back to linear but I think it has to have more than 2 lone pairs in order to distort it back to linear.
Fri Nov 20, 2020 3:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: axial and equatorial atoms
Replies: 2
Views: 24

### Re: axial and equatorial atoms

Equatorial atoms are the atoms that are bonded above or below the central atom and axial atoms are located around the atom on the same plane. When you change your perspective on the atom, I think the same atoms would be axial or equatorial. It depends on how many are bonded. For example, in the trig...
Sun Nov 15, 2020 1:18 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Hydrogen Bonding Vs Ion-Ion Interaction: Which One is Stronger?
Replies: 3
Views: 33

### Re: Hydrogen Bonding Vs Ion-Ion Interaction: Which One is Stronger?

Intramolecular forces will always be stronger than intermolecular forces because "intra" suggests that the bond in present WITHIN the molecule, which hold tighter that the forces BETWEEN molecules. Hydrogen bonding is an INTERmolecular force and the ion-ion forces are INTRAmolecular. So io...
Sun Nov 15, 2020 1:14 am
Forum: Lewis Structures
Topic: Nitrite vs Nitrate
Replies: 17
Views: 140

### Re: Nitrite vs Nitrate

Polyatomic ions that end in "-ite" will always have one less Oxygen than its "-ate" counterpart.
Sun Nov 15, 2020 1:12 am
Forum: Ionic & Covalent Bonds
Topic: A2.23 Textbook Problem
Replies: 3
Views: 31

### Re: A2.23 Textbook Problem

You're not looking for the charge of the compound because the compound should be neutral once it is complete. The charges of the atoms have to be balanced so if the cation and the anion have, respectively, a positive and negative charge that are opposite to each other than you only need one of each....
Sun Nov 15, 2020 1:09 am
Forum: Resonance Structures
Topic: Confusion on Potential Resonance Structure Diagram
Replies: 6
Views: 43

### Re: Confusion on Potential Resonance Structure Diagram

The dashed lines are present when the structure allows for resonance. It is representative of the fact that the average bond length for this structure is 1.5 because the double bond and the single bond have the potential to be in either place.
Sun Nov 15, 2020 1:07 am
Forum: Resonance Structures
Topic: lewis base or acid
Replies: 15
Views: 115

### Re: lewis base or acid

Lewis acid accept electrons while Lewis bases give the electrons.
Mon Nov 09, 2020 12:17 am
Forum: Trends in The Periodic Table
Topic: positive and negative ion
Replies: 14
Views: 74

### Re: positive and negative ion

Negative ions are larger than the positive or neutral counterparts.
Mon Nov 09, 2020 12:14 am
Forum: Lewis Structures
Topic: lewis structure
Replies: 17
Views: 49

### Re: lewis structure

The charge outside of the bracket represents the charge of the whole molecule. This can be seen in the charge placed on the molecular formula (such as NH4+) or by combining the formal charges of individual atoms.
Mon Nov 09, 2020 12:11 am
Forum: Dipole Moments
Topic: Sapling #17
Replies: 3
Views: 28

### Re: Sapling #17

I also agree with the above posts. The molecule is symmetrical, making the molecule itself non-polar. Though each bond is polar, they are evenly spaced out and counteracting each other. Since the molecule is non-polar, the only forces present would be LDF.
Mon Nov 09, 2020 12:07 am
Forum: Resonance Structures
Topic: Valence Electrons [ENDORSED]
Replies: 43
Views: 256

### Re: Valence Electrons[ENDORSED]

You can either calculate the number of valence electrons based on the number of electrons and then subtracting the inner ones or looking at the periodic table. Personally, I prefer the periodic table because it is faster and easier. You just look at what group the element is in and that is the numbe...
Fri Nov 06, 2020 4:07 pm
Forum: Ionic & Covalent Bonds
Replies: 38
Views: 222

As you go across a period, there are more protons in the nucleus. Because of this, the attraction to the electrons is stronger so they are pulled in tighter, making the atom smaller. My high school teacher always described it as "Coulombic attraction" and it increases as protons are added ...
Sun Nov 01, 2020 9:21 pm
Forum: Ionic & Covalent Bonds
Topic: intermolecular vs intramolecular
Replies: 17
Views: 298

### Re: intermolecular vs intramolecular

Intermolecular bonds are between molecules (LDF, Dipole-Dipole, Hydrogen). Intramolecular bonds are within molecules (Covalent, Ionic, Metallic).
Sun Nov 01, 2020 9:17 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling #24
Replies: 16
Views: 73

### Re: Sapling #24

I imagined how they would look when wrapped around in a circle. If they end in places that don't match up when wrapped and are not continuous, then the waves are not regular.
Sun Nov 01, 2020 9:15 pm
Forum: Ionic & Covalent Bonds
Topic: hydrogen
Replies: 19
Views: 240

### Re: hydrogen

A hydrogen bond is only possible between hydrogen and either fluorine, oxygen, or nitrogen. I always remember this by "a hydrogen bond can only be formed by a Freak Of Nature (FON)"
Sun Nov 01, 2020 9:12 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling Question Number 20
Replies: 4
Views: 37

### Re: Sapling Question Number 20

Ionization Energy is the energy required to remove an electron from an atom. Electron affinity is the energy that is released when an electron is added to the shell of an atom. And effective nuclear charge, if I remember correctly, is the positive charge experienced by an electron that has more than...
Sun Nov 01, 2020 9:08 pm
Forum: DeBroglie Equation
Replies: 21
Views: 129

Avogadro's number is 6.02 x 10^23. It identifies how many particles are in a mole and is often used in unit conversions between moles and particles.
Sun Nov 01, 2020 9:05 pm
Forum: Photoelectric Effect
Topic: Sapling HW Electron Affinity
Replies: 2
Views: 28

### Re: Sapling HW Electron Affinity

It becomes just unit conversion! eV to joules is given on the equation sheet (1 eV=1.602e-19) which then needs to be converted into kilojoules (1 kJ = 1000 J). Since it is eV per proton, you also have to multiply it by 6.02e23 so as to make it per mole.
Sun Oct 25, 2020 4:49 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Clarification on the "uncertainty" part of this equation
Replies: 7
Views: 100

### Re: Clarification on the "uncertainty" part of this equation

The indeterminacy equation gives the general idea of where the electron may be. It is impossible to tell with certainty where an electron is located, because of its wave and particle properties, so this equation is used to estimate position, velocity, and momentum.
Sun Oct 25, 2020 4:42 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Diffraction
Replies: 4
Views: 30

### Re: Diffraction

I think both because diffraction talks about how the waves interact with each other once they've gone through a barrier with holes :)
Sun Oct 25, 2020 4:36 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Amplitude
Replies: 16
Views: 85

### Re: Amplitude

Amplitude is unrelated to frequency and wavelength because it is solely the height of the waves and not the distance between them.
Sun Oct 25, 2020 12:15 pm
Forum: Photoelectric Effect
Topic: Mass of atoms
Replies: 18
Views: 105

### Mass of atoms

When it comes to certain questions, we need the mass of electrons or certain atoms in order to solve it. Does that always need to be in kilograms? And will we be given the value or do we need to memorize the basic ones?
Sun Oct 18, 2020 6:56 pm
Forum: Properties of Electrons
Topic: Light Emission
Replies: 4
Views: 44

### Re: Light Emission

I'm not sure about color but it does change the type of light. The amount of energy emitted changes from energy level to energy level and that changes type of the light. If the electron falls to level 1, the light is Ultraviolet, level 2 is visible and level 3 is infrared.
Sun Oct 18, 2020 6:51 pm
Forum: Photoelectric Effect
Topic: Wave Properties of Electrons
Replies: 3
Views: 19

### Re: Wave Properties of Electrons

I think it's in reference to light and how it acts both as groups of photons and waves. So electrons themselves aren't waves and require certain quanta of energy to eject but there are certain aspects of behavior that are similar to that of waves.
Sun Oct 18, 2020 6:49 pm
Forum: Properties of Light
Topic: Cross Country Analogy
Replies: 2
Views: 25

### Re: Cross Country Analogy

The connection was between the runners and the photoelectric effect and why increasing light intensity doesn't have an effect on ejected electrons. Increasing light intensity is adding to the number of photons, or in the analogy, the number of runners. But if the runners can't jump the barrier (or t...
Sun Oct 18, 2020 6:46 pm
Forum: Properties of Light
Topic: Frequency vs Wavelength
Replies: 22
Views: 141

### Re: Frequency vs Wavelength

Frequency and wavelength are inversely related, so as wavelength increases, frequency decreases and vice versa.
Sun Oct 18, 2020 6:42 pm
Forum: Photoelectric Effect
Topic: In a Vacuum
Replies: 7
Views: 35

### Re: In a Vacuum

To my understanding, if the electrons are interacting with the molecules in the air we wouldn't get an accurate representation of how the electrons react with the light. We can't get an accurate velocity of the escaping electrons because they're colliding with what's already in the air. It keeps the...
Fri Oct 09, 2020 2:23 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions Order
Replies: 31
Views: 241

### Re: Balancing Chemical Reactions Order

There's no correct order but I have found it easiest to balance polyatomic ions first, then elements that only exist in one molecule on each side, which normally leaves me with H's and O's. When it comes down to those, it normally isn't easier one way or another but for combustion, I tend to end wit...
Fri Oct 09, 2020 2:19 pm
Forum: Molarity, Solutions, Dilutions
Topic: NaHCO3
Replies: 2
Views: 48

### Re: NaHCO3

When a liquid is measured in a volumetric flask, the final volume will always match that of the flask. The initial 15 mL are poured in there in order to be diluted by an additional 85mL of water, meaning the final volume is 100mL.
Mon Oct 05, 2020 9:12 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Determining Molar Mass
Replies: 19
Views: 210

### Re: Determining Molar Mass

As a whole, once that number is plugged into different equations, it won't matter too much whether you used 15.999 or 16.000 because of the minute difference but I would use exactly the number seen on the periodic table that he provided. I think if the answer asks for a lot of significant figures, a...
Mon Oct 05, 2020 9:09 pm
Forum: Significant Figures
Topic: Sig Figs for elements on Periodic table
Replies: 14
Views: 141

### Re: Sig Figs for elements on Periodic table

Personally, I use four sig figs from the masses on periodic table and then adjust the final answer after every calculation is complete to get the most accurate and precise answer possible.
Mon Oct 05, 2020 6:44 pm
Forum: Balancing Chemical Reactions
Topic: Stoichemetric Coeffiecients
Replies: 12
Views: 141

### Re: Stoichemetric Coeffiecients

When it comes to stoichiometric coefficients being fractions, it can be helpful during the actual balancing process because it suggests that the final molecule was balanced. However, once the reaction is balanced, the whole reaction must be multiplied by the denominator of the fraction in order to r...