Search found 64 matches

by faithkim1L
Wed Jan 15, 2020 2:09 pm
Forum: Ideal Gases
Topic: ICE Table
Replies: 6
Views: 37

Re: ICE Table

An ICE table is used for equilibrium concentrations when we are unsure of the amount of change (in molarity) in the reactants as the chemical reaction moves to equilibrium. I stands for initial, which are the molarities that are given. Sometimes, the problem will only provide the moles and the conta...
by faithkim1L
Wed Jan 15, 2020 1:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: x is small approximation
Replies: 6
Views: 25

Re: x is small approximation

When Kc is a very small number, we know that there will be a large amount of reactant and a small amount of product (Kc is products over reactant, so the larger the denominator the smaller Kc). When Kc is 10^-3 or smaller, we can assume that the change (x) is so small that is makes a negligible effe...
by faithkim1L
Wed Jan 15, 2020 1:53 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Module 3 #19
Replies: 2
Views: 12

Re: Module 3 #19

First, convert moles given to molarity. It's a 10.0 L container, so the molarities of N2 and O2 are .0482 and .0933 respectively. With the equation given, Kc = [NO2]^2/[O2][N2]^2 Create the ICE table. N2 O2 N2O I .0482 .0933 0 C -2x -x 2x E .0482 - 2x .0933 - x 2x Kc = 2.0 x 10^-37 Kc = (2x)^2/(.933...
by faithkim1L
Wed Jan 15, 2020 1:48 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating Q
Replies: 16
Views: 40

Re: Calculating Q

When you calculate Q, you use the exact same process as if you were calculating for K. This means that you include all aqueous solutions and gases. Do not include solids or liquids in your calculations for Q (or K for that matter).
by faithkim1L
Wed Jan 15, 2020 1:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module Part 3, Question 7 (pre-assessment)
Replies: 4
Views: 629

Re: Module Part 3, Question 7 (pre-assessment)

First, you create your ice table. SO2. O2. SO3 I. .522 .633 0 C. - 2x -x 2x E. .522 - 2x .633 - x 2x Then, set up Kc and put in all the numbers/expressions. Kc = 5.66 x 10^-10 Kc = [SO3]^2/[SO2]^2[O2] 5.66 x 10^-10 = ((2x)^2)/(.522-2x)^2(.633-x) *Since Kc is so small, we know that the equilibrium re...
by faithkim1L
Fri Jan 10, 2020 11:51 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 34
Views: 348

Re: R in PV=nRT

R is the gas constant. I believe it will be given on the equation/constant sheet on tests.
by faithkim1L
Fri Jan 10, 2020 11:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Le Chatelier's Principle
Replies: 7
Views: 30

Re: Le Chatelier's Principle

Le Chatelier's Principle basically just says that a chemical equation will move to decrease the amount of change as much as possible. So if there is a chemical equation and product has been added, the equation will move "away" from the products and towards the reactants (reverse reaction).
by faithkim1L
Fri Jan 10, 2020 11:48 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Using Kc Vs Kp
Replies: 7
Views: 30

Re: Using Kc Vs Kp

Kp is used for gases. Kc can be used for aqueous solutions. It's best to just go by the equation. Remember Kp is in pressure units and Kc is for concentration (M).
by faithkim1L
Fri Jan 10, 2020 11:22 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework 1
Replies: 18
Views: 103

Re: Homework 1

Most TAs correct HW based on correctness and completion. There is the answer solution book to check answers, and just make sure you do five problems a week.
by faithkim1L
Fri Jan 10, 2020 11:20 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework 1
Replies: 18
Views: 103

Re: Homework 1

Homework is usually due during discussion, but for the first week it was due after lecture on Friday.
by faithkim1L
Fri Jan 10, 2020 11:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Ratios
Replies: 7
Views: 33

Re: ICE Table Ratios

As long as the ratio is the same as the ratio of the balanced equation, it doesn't matter what the actual numbers are.
by faithkim1L
Sat Dec 07, 2019 8:18 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Equilibrium calculations
Replies: 6
Views: 43

Re: Equilibrium calculations

I think we only need to know the concepts and the logistics of Ka, but we won't have to do any calculations since we haven't learned everything about weak acids. We will, however, need to know about strong acids and its dissociation properties.
by faithkim1L
Sat Dec 07, 2019 8:15 pm
Forum: Calculating the pH of Salt Solutions
Topic: Titrations
Replies: 6
Views: 58

Re: Titrations

I think most of it is conceptual. Titrations allow us to find the molarity of an unknown solution using another solution with a known molarity. We use the stoichiometric point/equivalence point to figure out the molarity of the unknown solution.
by faithkim1L
Sat Dec 07, 2019 8:10 pm
Forum: Polyprotic Acids & Bases
Topic: amphiprotic vs amphoteric
Replies: 2
Views: 24

Re: amphiprotic vs amphoteric

Amphiprotic means that the molecule can accept or donate an H+. Amphoteric means that the molecule can can act as a base and an acid. If a molecule is amphiprotic, it's amphoteric, but it doesn't necessarily work the other way (think Lewis acids - relationship with electrons).
by faithkim1L
Sat Dec 07, 2019 8:08 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Negative pH
Replies: 5
Views: 33

Re: Negative pH

The pH would only be negative if it's a super acid. In these cases, Ka is larger than 1. I don't think we need to know this for the final though.
by faithkim1L
Sat Dec 07, 2019 8:06 pm
Forum: Air Pollution & Acid Rain
Topic: dirty/clean coal
Replies: 6
Views: 55

Re: dirty/clean coal

Dirty coal has a larger amount of S in it. I think that's all we need to know.
by faithkim1L
Sat Nov 30, 2019 12:10 pm
Forum: Student Social/Study Group
Topic: Preparing for the final
Replies: 25
Views: 150

Re: Preparing for the final

I think practice problems are a really good idea, on top of maybe some reinforcement through the step-up sessions and online videos.
by faithkim1L
Sat Nov 30, 2019 12:07 pm
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equations
Replies: 5
Views: 32

Re: Net Ionic Equations

There are solubility rules that help you identify which ones will dissociate in water and become aqueous, and those that will not. The best way to know is just to memorize the solubility rules. It was mandatory in HS AP Chem to know them, but I'm not sure if Lavelle will have us memorize them too.
by faithkim1L
Sat Nov 30, 2019 12:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Polarity
Replies: 10
Views: 66

Re: Determining Polarity

Drawing net dipoles helps a lot, but you need to make sure that you are not just cancelling dipoles that seem opposite each other. For example, in CHCl3, you can't cancel the dipoles of Cl that are across from each other, because the bond angle is actually 109.5 and not 90/180. Also, when there is a...
by faithkim1L
Sat Nov 30, 2019 12:03 pm
Forum: General Science Questions
Topic: test taking nervousness
Replies: 19
Views: 146

Re: test taking nervousness

Doing practice problems really help. It's the best way to get used to the types of problems that will be on the test, and it will also reinforce the concepts that you're learning for the test.
by faithkim1L
Sat Nov 30, 2019 12:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw Shape
Replies: 12
Views: 74

Re: Seesaw Shape

The bond angles for the seesaw molecule will be slightly less than 90 and 120 degrees, since the lone pair affects the bonding angles.
by faithkim1L
Sun Nov 24, 2019 5:19 pm
Forum: Naming
Topic: using brackets
Replies: 5
Views: 23

Re: using brackets

Anything inside the brackets are part of the main coordination compound.
by faithkim1L
Sun Nov 24, 2019 5:18 pm
Forum: Lewis Acids & Bases
Topic: lewis vs. bronsted
Replies: 10
Views: 54

Re: lewis vs. bronsted

A Bronsted acid is a proton donor while a Lewis acid accepts an electron pair.
by faithkim1L
Sun Nov 24, 2019 5:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 23
Views: 121

Re: Seesaw

Because there is a lone pair, the angles should be slightly less than 90 and 120.
by faithkim1L
Sun Nov 24, 2019 5:16 pm
Forum: Hybridization
Topic: Sigma and Pi bonds
Replies: 13
Views: 55

Re: Sigma and Pi bonds

When you draw the bonds, you draw them as normal and just label each bond below or beneath the bond with a pi or sigma symbol.
by faithkim1L
Sun Nov 24, 2019 5:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE Format
Replies: 34
Views: 117

Re: AXE Format

When there is only an X or an E, it is implied that there is one of those.
by faithkim1L
Sun Nov 24, 2019 5:14 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: AXE
Replies: 6
Views: 48

Re: AXE

It allows you to picture the molecule, allowing you to know how many pairs of lone pair electrons there are and how many atoms the central atom is bonded to.
by faithkim1L
Sat Nov 16, 2019 3:18 pm
Forum: Dipole Moments
Topic: Hydrogen bonds
Replies: 17
Views: 85

Re: Hydrogen bonds

Hydrogen bonds only form between H atoms and N, O, and F.
by faithkim1L
Sat Nov 16, 2019 3:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining if a molecule is polar or non polar
Replies: 9
Views: 48

Re: Determining if a molecule is polar or non polar

We don't have to memorize the electronegativity chart. It's easier to use the net dipole to figure out if the molecule is polar or not. For example, for CH3Cl, there is a net dipole towards the chlorine atom, making the whole molecule. However, for CH4, there is no net dipole which makes the molecul...
by faithkim1L
Sat Nov 16, 2019 3:15 pm
Forum: Sigma & Pi Bonds
Topic: Sigma & Pi Bonds
Replies: 4
Views: 27

Re: Sigma & Pi Bonds

Sigma bonds are the first bonds between any two atoms. So, for single bonds, there are only sigma bonds. However, for double and triple bonds, pi bonds are the other bonds (2nd and 3rd bonds) formed between two atoms. So for a double bond, there will be one sigma bond and one pi bond. The pi bonds a...
by faithkim1L
Sat Nov 16, 2019 3:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: test 2
Replies: 13
Views: 74

Re: test 2

If I remember correctly, hybridization will not be on Test 2. The test covers material from the midterm on. The lecture on Monday, about sigma and pi bonds, will be on the test.
by faithkim1L
Sat Nov 16, 2019 3:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 9
Views: 47

Re: Bond Angles

The angles for the molecular shapes are all standardized. When a molecule is polar, the bond angles will change, but we do not need to know the exact values. All we need to indicate is that the angles either decrease or increase (i.e. with lone pairs of electrons instead of bonding pairs).
by faithkim1L
Sat Nov 09, 2019 4:53 pm
Forum: Dipole Moments
Topic: London forces
Replies: 9
Views: 52

Re: London forces

London Dispersion Forces (LDF) are classified as universal because any molecule or atom with any number of electrons will experience some kind of movement. Since electrons are not in a "fixed" position (they are in an electron cloud and move around there), there will be some areas that are...
by faithkim1L
Sat Nov 09, 2019 4:51 pm
Forum: General Science Questions
Topic: Rusty on High School Chem [ENDORSED]
Replies: 168
Views: 102283

Re: Rusty on High School Chem [ENDORSED]

The modules on Lavelle's website are extremely helpful, especially when you just want to go over the concepts that you went over in class. Also, the step up classes are helpful and office hours are too. I recommend just going through a lot of the chem problems from the textbook (the odd ones, since ...
by faithkim1L
Sat Nov 09, 2019 4:48 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: Boiling Points
Replies: 6
Views: 51

Re: Boiling Points

When you draw the lewis structure for both AsF3 and AsF5, the former has a lone pair of electrons over As. This results in polarity, and there are dipole-dipole moments in the molecule. However, in AsF5, there are no lone pairs on As, meaning that the whole molecule is nonpolar and has no dipole-dip...
by faithkim1L
Sat Nov 09, 2019 4:45 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: Intermolecular forces
Replies: 3
Views: 21

Re: Intermolecular forces

Hydrogen bonds are the strongest IMFs. They are significantly stronger than London Dispersion Forces because those are only temporary and are not necessarily "permanent." They tend to move around more than hydrogen bonds, which are usually always polarized.
by faithkim1L
Sat Nov 09, 2019 4:44 pm
Forum: SI Units, Unit Conversions
Topic: Memorizing Conversions
Replies: 23
Views: 216

Re: Memorizing Conversions

It's really nice to know the conversions at the top of your head so you're not looking around the reference sheet for them. However, I believe Lavelle is quite generous and provides most of the formulas and conversions for the exams.
by faithkim1L
Sat Nov 02, 2019 10:13 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis Structure for Ionic Bonds
Replies: 4
Views: 34

Re: Lewis Structure for Ionic Bonds

Charged molecules are completely bracketed with the total charge written outside in the top right corner outside the brackets.
by faithkim1L
Sat Nov 02, 2019 10:08 pm
Forum: Lewis Structures
Topic: Expanded Octet
Replies: 3
Views: 25

Re: Expanded Octet

Elements in or after the third period have expanded octets. The central elements usually end up with the expanded octets (the extra pairs of electrons).
by faithkim1L
Sat Nov 02, 2019 10:06 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7741
Views: 1058249

Re: Post All Chemistry Jokes Here

All the chemistry jokes argon!
by faithkim1L
Sat Nov 02, 2019 10:04 pm
Forum: Resonance Structures
Topic: Drawing Resonance Structures
Replies: 3
Views: 36

Re: Drawing Resonance Structures

When a molecule has resonance, you usually have to draw all the possible structures.
by faithkim1L
Sat Nov 02, 2019 10:02 pm
Forum: Lewis Structures
Topic: drawing lewis structures
Replies: 5
Views: 49

Re: drawing lewis structures

Br has an expanded octet in this case. Any element in or after period 3 can have an expanded octet.
by faithkim1L
Sat Nov 02, 2019 10:00 pm
Forum: Ionic & Covalent Bonds
Topic: ionic vs. covalent
Replies: 7
Views: 41

Re: ionic vs. covalent

Covalent bonds share electrons across the elements in the molecule. In ionic bonds, the cation "gives" its electron(s) to the anion.
by faithkim1L
Sun Oct 27, 2019 5:09 pm
Forum: Quantum Numbers and The H-Atom
Topic: determining the number of orbitals
Replies: 7
Views: 57

Re: determining the number of orbitals

l=0; s
l=1; p
l=2; d
l=3; f
by faithkim1L
Sun Oct 27, 2019 5:08 pm
Forum: Student Social/Study Group
Topic: Miderm Review
Replies: 10
Views: 109

Re: Miderm Review

Sapling Learning is a good resource to use other than the midterm review sessions. Doing all the recommended practice problems on the outlines is also really helpful.
by faithkim1L
Sun Oct 27, 2019 5:07 pm
Forum: Student Social/Study Group
Topic: Study Tips
Replies: 58
Views: 635

Re: Study Tips

Studying chemistry is really just practice. I find it best to do practice problems. Lavelle's Step Up Program is also really helpful if you're struggling with the material in general.
by faithkim1L
Sun Oct 27, 2019 5:06 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons
Replies: 16
Views: 108

Re: Valence Electrons

Valence electrons are the number of electrons in the valence (last) shell of the atom. For example, Cl has 7 valence electrons.
by faithkim1L
Sun Oct 27, 2019 5:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions to Electron Configuration
Replies: 7
Views: 37

Re: Exceptions to Electron Configuration

Cu and Cr are the only exceptions.
by faithkim1L
Sat Oct 19, 2019 10:26 pm
Forum: Properties of Electrons
Topic: mass of electron, proton, neutron
Replies: 7
Views: 47

Re: mass of electron, proton, neutron

I am pretty sure that these are provided on the 'reference sheet' that Lavelle gives us. It will probably be similar to the one on the first test we took Week 3.
by faithkim1L
Sat Oct 19, 2019 10:20 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Inner e- and Outer e-
Replies: 14
Views: 81

Re: Inner e- and Outer e-

In multi-electron atoms, there is a shielding effect that causes the outer electrons to be 'shielded' from the nucleus by the inner electrons. Because of this, there is a lesser attraction between the outer electrons and the nucleus, and this results in a larger atomic radius.
by faithkim1L
Sat Oct 19, 2019 10:18 pm
Forum: General Science Questions
Topic: Tests
Replies: 9
Views: 70

Re: Tests

It's very helpful to know the basic conversions, especially the metric system (because they're all multiples of ten). However, I believe that on the tests, Lavelle provides some of the conversions as a reference sheet.
by faithkim1L
Sat Oct 19, 2019 10:16 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Which Element to Use in Electron Configurations
Replies: 5
Views: 31

Re: Which Element to Use in Electron Configurations

When shortening the electron configuration to make it easier to sort through, people use the noble gas and write out the last line of the electron configuration. However, you can also just write out the whole thing.
by faithkim1L
Sat Oct 19, 2019 10:13 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Unit for Avogadro's Number
Replies: 10
Views: 121

Re: Unit for Avogadro's Number

The answer depends on each problem. Avogadro's number represents the number of (mcls, atoms, ions) per mol of the given element or compound.
by faithkim1L
Sat Oct 12, 2019 4:35 pm
Forum: *Black Body Radiation
Topic: Black Body Radiation
Replies: 12
Views: 106

Re: Black Body Radiation

Black body radiation is not necessary to the course. It's more of a physics experiment.
by faithkim1L
Sat Oct 12, 2019 4:34 pm
Forum: Properties of Light
Topic: Light Intensity
Replies: 6
Views: 27

Re: Light Intensity

Yes, this is correct. The light intensity is directly related to the number of photons.
by faithkim1L
Sat Oct 12, 2019 4:27 pm
Forum: Properties of Light
Topic: Quantum Levels
Replies: 9
Views: 65

Re: Quantum Levels

There is no maximum to the number of energy levels. But in the diagram that is drawn in class, the energy levels get closer and closer together.
by faithkim1L
Sat Oct 12, 2019 4:18 pm
Forum: Properties of Electrons
Topic: Electron After Excited State
Replies: 7
Views: 31

Re: Electron After Excited State

An electron is excited and rises to a higher energy level. However, electrons can release energy in the form of a photon. This will cause the electron to eventually fall back to its original state.
by faithkim1L
Sat Oct 12, 2019 4:12 pm
Forum: Properties of Light
Topic: Frequency vs. Wavelength
Replies: 15
Views: 92

Re: Frequency vs. Wavelength

Frequency and wavelength are inversely related. So if frequency increases, then wavelength decreases. Frequency is in Hz (s^-1), and wavelength is usually in nm. However, if you're finding wavelength to put it into another equation, make sure the units cancel out.
by faithkim1L
Tue Oct 01, 2019 10:55 pm
Forum: Balancing Chemical Reactions
Topic: Tips on what number to multiply the entire equation if needed
Replies: 8
Views: 111

Re: Tips on what number to multiply the entire equation if needed

The best way to ensure that you will end up with whole numbers on all of the stoichiometric coefficients is to multiply all the coefficients by the common denominator of the fractions. For example, if you had two fractions as stoichiometric coefficients with the denominators 2 and 3, you should mult...
by faithkim1L
Tue Oct 01, 2019 10:48 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Units in Answer
Replies: 18
Views: 169

Re: Units in Answer

Usually, the problem will ask for the amount in moles or in grams. When this is not the case, I usually read the context of the problem. In labs, you usually just use grams. It's not very likely that you will use moles in the lab.
by faithkim1L
Tue Oct 01, 2019 10:45 pm
Forum: Significant Figures
Topic: Rounding
Replies: 3
Views: 40

Re: Rounding

The only difference between rounding and chemistry rounding is when the last digit is a 5. When you have a number that ends in 5 (ex: 3.65), you round up or down to the nearest even number. In the example, it would be 3.6. However, if you had 4.75, you would round up to 4.8.
by faithkim1L
Tue Oct 01, 2019 10:43 pm
Forum: Empirical & Molecular Formulas
Topic: homework problem E9
Replies: 6
Views: 82

Re: homework problem E9

The molar mass (MM) is the mass of the whole molecule, which includes the heptahydrate. Hepta means 7, so you need to multiply 18.02 g by 7 in order to get the mass of the heptahydrate. After that, you can just add the MM of the molecule MgSO4 to find the total molar mass of the molecule.
by faithkim1L
Tue Oct 01, 2019 10:41 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Balancing Equations [ENDORSED]
Replies: 25
Views: 450

Re: Balancing Equations [ENDORSED]

If leaving the coefficients in fractions when solving for them is helpful, then do that first. After you balance the equation, you can just multiply all the coefficients by the common denominator for the fractional stoichiometric coefficients.
by faithkim1L
Tue Oct 01, 2019 10:40 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Balancing Equations [ENDORSED]
Replies: 25
Views: 450

Re: Balancing Equations [ENDORSED]

If leaving the coefficients in fractions when solving for them is helpful, then do that first. After you balance the equation, you can just multiply all the coefficients by the common denominator for the fractional stoichiometric coefficients.

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